NOS HYDROGRAPHIC SURVEYS SPECIFICATIONS

AND DELIVERABLES

April 2009

U.S. Department of Commerce

National Oceanic and Atmospheric Administration
Contents

1 Introduction 1

1.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Changes from April 2008 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 Datums 3

2.1 Horizontal Datum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Sounding Datum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.3 Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 Hydrographic Position Control 4

3.1 Horizontal Position Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.2 Differential Global Positioning System . . . . . . . . . . . . . . . . . . . . . . . 4

3.2.1 DGPS Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.2.2 DGPS Site Confirmation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.2.3 Other GPS Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Tides and Water Levels Requirements 6

4.1 General Project Requirements and Scope . . . . . . . . . . . . . . . . . . . . . 6

4.1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.1.2 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.1.3 Planning and Preliminary Tidal Zoning . . . . . . . . . . . . . . . . . . . 7

4.1.4 NOS Control Stations and Data Quality Monitoring . . . . . . . . . . . . 7

4.1.5 General Data and Reference Datum Requirements . . . . . . . . . . . 8

4.1.6 Error Budget Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.2 Data Collection and Field Work . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.2.1 Water Level Station Requirements . . . . . . . . . . . . . . . . . . . . . 9

4.2.2 Water Level Measurement Systems and Data Transmissions . . . . . 10

4.2.3 Station Installation, Operation and Removal . . . . . . . . . . . . . . . 12
4.2.4 Tide Staffs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.2.5 Bench Marks and Leveling . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.2.6 Water level Station Documentation . . . . . . . . . . . . . . . . . . . . . 20

4.2.7 Additional Field Requirements . . . . . . . . . . . . . . . . . . . . . . . . 20

4.2.8 Geodetic Connections and Datums Relationship . . . . . . . . . . . . . 21

4.2.9 NAVD 88 Level Tie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.2.10GPS Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4.2.11North American Datum (NAD 83) GPS Tie . . . . . . . . . . . . . . . . . 25

4.2.12GPS Data Processing Using OPUS . . . . . . . . . . . . . . . . . . . . . . 26

4.2.13OPUS DB Preliminary Information . . . . . . . . . . . . . . . . . . . . . . 27

4.2.14NAVD 88 GPS Tie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.3 Data Processing and Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.3.1 Data Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.3.2 Data Processing and Tabulation of the Tide . . . . . . . . . . . . . . . . 29

4.3.3 Computation of Monthly Means . . . . . . . . . . . . . . . . . . . . . . . 30

4.3.4 Data Editing and Gap Filling Specifications . . . . . . . . . . . . . . . . 30

4.4 Computation of Tidal Datums and Water Level Datums . . . . . . . . . . . . . 34

4.4.1 National Tidal Datum Epoch . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.4.2 Computational Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.4.3 Tidal Datum Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.4.4 Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.5 Final Zoning and Tide Reducers . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.5.1 Water Level Station Summaries . . . . . . . . . . . . . . . . . . . . . . . 50

4.5.2 Construction of Final Tidal Zoning Schemes . . . . . . . . . . . . . . . . 51

4.5.3 Tide Reducer Files and Final Tide Note . . . . . . . . . . . . . . . . . . . 51

4.6 Data Submission Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4.6.1 Station Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4.6.2 GPS Project Documentation . . . . . . . . . . . . . . . . . . . . . . . . . 58

4.6.3 Water Level Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

4.6.4 Tabulations and Tidal Datums . . . . . . . . . . . . . . . . . . . . . . . . 76

4.6.5 Tide Reducers and Final Zoning and Final Tide Note . . . . . . . . . . . 82

4.6.6 Submission and Deliverables – Documentation and Time lines . . . . 82

4.7 Guidelines and References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5 Depth Sounding 87

5.1 Multibeam and Other Echosounders . . . . . . . . . . . . . . . . . . . . . . . . 87

5.1.1 Accuracy and Resolution Standards . . . . . . . . . . . . . . . . . . . . 87

5.1.1.1 Accuracy Standards . . . . . . . . . . . . . . . . . . . . . . . . . 87

5.1.1.2 Multibeam Resolution Standards . . . . . . . . . . . . . . . . . 88

5.1.1.3 Gridded Data Specifications . . . . . . . . . . . . . . . . . . . . 88

5.1.2 Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

5.1.2.1 Object Detection Coverage . . . . . . . . . . . . . . . . . . . . 90

5.1.2.2 Complete Multibeam Coverage . . . . . . . . . . . . . . . . . . 91

5.1.2.3 Set Line Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . 92

5.1.3 Corrections to Echo Soundings . . . . . . . . . . . . . . . . . . . . . . . 92

5.1.3.1 Instrument Error Corrections . . . . . . . . . . . . . . . . . . . . 93

5.1.3.2 Draft Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . 94

5.1.3.3 Speed of Sound Corrections . . . . . . . . . . . . . . . . . . . . 95

5.1.3.4 Attitude Corrections . . . . . . . . . . . . . . . . . . . . . . . . . 97

5.1.3.5 Error Budget Analysis for Depths . . . . . . . . . . . . . . . . . 97

5.1.3.6 Uncertainty Budget Analysis for Depths . . . . . . . . . . . . 99

5.1.4 Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

5.1.4.1 Multibeam Sonar Calibration . . . . . . . . . . . . . . . . . . . . 100

5.1.4.2 Positioning System Confidence Checks . . . . . . . . . . . . . 101

5.1.4.3 Crosslines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

5.2 Lidar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

5.2.1 Accuracy and Resolution Standards . . . . . . . . . . . . . . . . . . . . 102

5.2.1.1 Lidar Resolution Standards . . . . . . . . . . . . . . . . . . . . . 102

5.2.1.2 Gridded Data Specifications . . . . . . . . . . . . . . . . . . . . 103

5.2.2 Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

5.2.3 Corrections to Lidar Soundings . . . . . . . . . . . . . . . . . . . . . . . 104

5.2.3.1 Instrument Error Corrections . . . . . . . . . . . . . . . . . . . . 105

5.2.4 Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

5.2.4.1 Lidar Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

5.2.4.2 Positioning System Confidence Checks . . . . . . . . . . . . . 105

5.2.4.3 Crosslines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
6 Towed Side Scan Sonar 107

6.1 Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

6.2 Side Scan Acquisition Parameters and Requirements . . . . . . . . . . . . . . 107

6.2.1 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

6.2.2 Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

6.2.3 Towfish Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

6.2.4 Horizontal Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

6.3 Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

6.3.1 Confidence Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

6.3.2 Significant Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.3.3 Contact Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.3.4 Identification of Potential Field Examinations . . . . . . . . . . . . . . . 109

7 Other Data 110

7.1 Bottom Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

7.2 Aids to Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

8 Deliverables 111

8.1 Field Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

8.1.1 Progress Sketch and Survey Outline . . . . . . . . . . . . . . . . . . . . 111

8.1.2 Danger to Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

8.1.2.1 Charted Feature Removal Request . . . . . . . . . . . . . . . . 113

8.1.3 Descriptive Report (DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

8.1.4 Descriptive Report Supplemental Reports . . . . . . . . . . . . . . . . . 123

8.1.4.1 Data Acquisition and Processing Report . . . . . . . . . . . . . 123

8.1.4.2 Horizontal and Vertical Control Report . . . . . . . . . . . . . . 125

8.2 S-57 Feature File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

8.2.1 S-57 Attribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

8.2.2 Cartographic Specifications and Conventions . . . . . . . . . . . . . . 132
8.3 Side Scan Sonar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

8.3.1 Side Scan Sonar Mosaic . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

8.3.2 Side Scan Sonar Contact List . . . . . . . . . . . . . . . . . . . . . . . . 134

8.3.3 Data Acquisition and Processing Abstracts . . . . . . . . . . . . . . . . 136

8.4 Digital Data Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

8.4.1 Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

8.4.2 Single-beam Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

8.4.3 Shallow-Water Multibeam and Lidar Data . . . . . . . . . . . . . . . . . 139

8.4.4 Side Scan Sonar Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

8.4.5 Other Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

A Appendix 1: Tide Station Report and Next Generation Water Level Measurement System Site Report 142

B Appendix 2: Descriptive Report Cover Sheet (NOAA Form 76-35A) 147

C Appendix 3: Descriptive Report Title Sheet (NOAA Form 77-28) 148

D Appendix 4: Abstract of Times of Hydrography for Smooth Tides or Water Levels 149

E Appendix 5: Example Request for Smooth Tides/Water Levels Letter 150

F Appendix 6: Danger to Navigation Report 151

G Appendix 7: Data Acquisition and Processing Report 153

H Appendix 8: Rock Attribution 154

I Appendix 9: Statistics Spreadsheet Example 155
1 Introduction

These technical specifications detail the requirements for hydrographic surveys to be

undertaken either by National Oceanic and Atmospheric Administration (NOAA) field

units or by organizations under contract to the Director, Office of Coast Survey (OCS),

National Ocean Service (NOS), NOAA, U.S. Department of Commerce.

The specifications described herein are based in part on the International Hydrographic

Organization’s Standards for Hydrographic Surveys, Special Publication 44, Fourth Edition, April 1998, specifically for Order 1 surveys. Hydrographic surveys classified as

Order 1 are intended for harbors, harbor approach channels, recommended tracks,

inland navigation channels, coastal areas of high commercial traffic density, and are

usually in shallower areas less than 100 meters water depth. Additional details for the

specific project areas, including any modifications to the specifications in this manual,

will be provided in Hydrographic Survey Project Instructions for NOAA field units or the

Statement of Work for contractors.

If a hydrographer has any questions on the interpretation of these Specifications or

feels that there may be a “better way” to provide a deliverable, they should contact

the COTR or appropriate NOAA Program Office to discuss and clarify the issue. The

Specifications will continue to evolve and can only improve with the input of all users.

1.1 Definition

The term “hydrographer” as used through this document, refers to: (a) the chief of

party or officer in charge, when the survey is being conducted by NOAA field units, or

(b) the contractor where the work is being performed for NOAA under contract.

1.2 Changes from April 2008

Chapter 5 ”Depth Sounding”

1. Minor changes were made to section 5.1.1.3 Gridded Data Specifications to clarify

grid resolution and requirements.

2. Section 5.1.1.3 Gridded Data Specifications was revised to consider the scale of

the survey when choosing soundings as well as changing the 30m depth to 20m.

3. Section 5.1.2.1 Object Detection Coverage has been revised to include more accurate grid resolution thresholds.

4. Section 5.1.3.6 Uncertainty Budget Analysis for Depths has been added to the

document.

1
Chapter 8 ”Deliverables”

1. Section 8.1.2 Danger to Navigation has been updated for the contractor to include:

A chartlet showing the DTON on the largest scale chart and screen captures of Side

Scan Sonar or Multibeam images of the DTON.

2. Section 8.2 Feature File has been revised to include that the deliverables for a

NOAA field unit survey shall be delivered via Pydro files and/or notebook files.

2
2 Datums

2.1 Horizontal Datum

All positions will be referenced to the North American Datum of 1983 (NAD 83). This

datum must be used throughout a survey project for everything that has a geographic

position or for which a position is to be determined. Those documents used for comparisons, such as charts, junctional surveys, and prior surveys, must be referenced or

adjusted to NAD 83. In addition, all software used on a survey must contain the correct

datum parameters.

The only exception for the NAD83 datum requirement is that the S-57 feature file will be

in the WGS84 datum to comply with the international S-57 specifications (see Section

8.2). All data shall be collected in the NAD83 datum and then transformed to the WGS84

datum in the S-57 feature file.

2.2 Sounding Datum

All sounding data will be reduced to Mean Lower Low Water (MLLW). Heights of bridges

and overhead cables will be referenced to Mean High Water (MHW).

2.3 Time

Coordinated Universal Time (UTC) will be used for all time records.

3
3 Hydrographic Position Control

3.1 Horizontal Position Accuracy

The NOS specification for hydrographic positioning is that the total error in position of

soundings, at the 95 percent confidence level, will not exceed 5 meters + 5 percent of

the depth. This accuracy requirement is independent of survey scale.

For hydrographic surveys using single-beam echosounders, the accuracy of the vessel

position can be considered the accuracy of the sounding obtained by that vessel, taking

into account transducer offsets. However, for multibeam surveys, due to the oblique

sounding pattern, the position of a sounding may be at some distance from the vessel position. The accuracy requirement for the vessel position will depend upon how

accurately the sounding is positioned relative to the vessel. That, in turn, will depend

upon the characteristics of the multibeam system, depth of water, the accuracy with

which heave, roll, pitch, heading, and latency are accounted for and applied, and the

reliability with which the speed of sound profile is known. Refer to section 8.1 regarding

horizontal reporting requirements.

3.2 Differential Global Positioning System

DGPS is the primary positioning system currently used for hydrographic surveys. DGPS

correctors can be obtained either through the U.S. Coast Guard (USCG) Maritime DGPS

Service or other differential services provided they meet the accuracy requirement in

Section 3.1.

3.2.1 DGPS Specifications

Unless specified otherwise in the Hydrographic Survey Project Instructions or Statement of Work, the following specifications are recommended when DGPS is used as the

primary positioning system:

• GPS receiver(s) aboard the vessel will be configured such that satellites below 8

degrees above the horizon will not be used in position computations.

• The age of pseudo-range correctors used in position computation should not exceed 20 seconds; and any horizontal positioning interpolation must not exceed the

accuracy requirement in Section 3.1.

• Horizontal Dilution of Precision (HDOP) will be monitored and recorded, and should

not exceed 2.5 nominally. Satellite geometry alone is not a sufficient statistic for

determining horizontal positioning accuracy. Other variables, including satellite

pseudorange residuals can be used in conjunction with HDOP to estimate DGPS

horizontal accuracy.

• A minimum of four satellites will be used to compute all positions.

• Horizontal and vertical offsets between the GPS antenna and transducer(s) will be

observed and applied in no coarser than 0.1 m increments.

4
Any deviations from the above specifications shall be clearly documented in the Descriptive Report with an explanation and supporting data to show that the resulting

positions meet the accuracy requirement in Section 3.1.

3.2.2 DGPS Site Confirmation

If any non-USCG differential reference stations are used, the hydrographer shall annually conduct a certification to ensure that no multipath or other site specific problems

exist. Using a receiver established over a known point, create a plot to compare positions generated (at least one per second for 24 hours) to the known position and

prove that the position accuracy requirement of Section 3.1 is met. Include plots in the

Horizontal Control Report for each project (see section 8.1.4.2) .

3.2.3 Other GPS Techniques

Real Time Kinematic (RTK) and Post Processed Kinematic (PPK) may be used for positioning during hydrographic surveys. If RTK or PPK techniques are used, the hydrographer must ensure that all positions meet the accuracy requirements of Section 3.1.

Many vessels receive survey positions from a DGPS aided inertial navigation system

(e.g. POS MV). A high quality inertial system may be able to maintain accurate positions

for several minutes after loss of differential correctors. Also, age of correctors, satellite

elevation variables, etc., may not be configurable. When using DGPS aided inertial

navigation systems, the DGPS recommended configurations of Section 3.2.1 may not

apply. However, whatever positioning system is used, the hydrographer must always

ensure that positions meet the accuracy requirements of Section 3.1.

The hydrographer must describe the quality control checks used to ensure positional

accuracy was met in the Data Acquisition and Processing Report (DAPR) and/or Descriptive Report (DR).

5
4 Tides and Water Levels Requirements

4.1 General Project Requirements and Scope

4.1.1 Scope

The requirements and specifications contained in this section cover the water level

and vertical datum requirements for operational support of hydrographic surveys and

photogrammetric surveys conducted as part of the NOAA Nautical Charting Program.

The scope of this support is comprised of the following functional areas:

1. Tide and water level requirements planning

2. Preliminary tidal zoning development

3. Control water level station operation, monitoring, and maintenance

4. Subordinate water level station installation, operation, monitoring, maintenance,

and removal

5. Data quality control, processing, and tabulation

6. Tidal datum computation and tidal datum recovery

7. Generation of water level reducers and final tidal zoning

8. Quality control check of contractor submitted data to CO-OPS

For NOAA in-house surveys hydrographic survey, personnel from the NOAA’s National

Ocean Service (NOS) Center for Operational Oceanographic Products and Services (COOPS) are responsible for functional areas 1, 2, 3, 5, 6 and 7. NOS hydrographers shall

be responsible for functional area 4 above.

For NOAA contract hydrographic surveys, NOS CO-OPS personnel are responsible for

functional areas 1, 2, 3 and 8. NOAA contract hydrographers shall be responsible for

functional areas 4 through 7 above. NOS CO-OPS will be responsible for operating,

maintaining, and processing data from the National Water Level Observation Network

(NWLON) control stations.

4.1.2 Objectives

The work performed according to the requirements and specifications of this document

is required for NOS major program areas of navigational products and services. The

first objective is to provide time series of water level reducers that can be applied

to hydrographic soundings so that they can be corrected to chart datum. A second

objective is to establish and/or recover tidal datums relative to local benchmarks at

each station that can be used for continuing and future hydrographic surveys in the

area. A third objective is to provide new information or updated information that can

be used to update NOAA tide prediction products and tidal zoning for promote safe

navigation applications.

6
4.1.3 Planning and Preliminary Tidal Zoning

CO-OPS is responsible for all planning of tide requirements for NOS hydrographic surveys. CO-OPS will analyze historical data and tidal characteristics for each project area,

specify operational NOS control stations, specify subordinate tide station locations to

be installed, and provide the preliminary tidal zoning to be used during survey operations. CO-OPS will provide 6-minute interval tide predictions relative to chart datum

for appropriate NOS control stations prior to each survey and will also provide historical published bench mark information available for all historical tide stations specified

for reoccupation. If CO-OPS provides a new preliminary tidal zoning scheme, the contractor must use that zoning scheme first for each project, and then, may generate a

new scheme if the one provided is not adequate. At the conclusion of the survey, the

contractor shall suspend the use of preliminary zoning scheme and develop final zoning scheme using correctors derived from the subordinate stations installed during the

survey. Refer to Section 4.5.2 for further details.

4.1.4 NOS Control Stations and Data Quality Monitoring

National Water Level Observation Network

CO-OPS manages the NWLON of approximately 200 (as of October 2007) continuously

operating water level observation stations in the U.S. coastal zone, including the Great

Lakes. As most of these stations are equipped with satellite radios, near real-time

(within about 30 minutes of collection) raw data are made available to all users through

the CO-OPS Web homepage at www.tidesandcurrents.noaa.gov. Verified products, such

as edited 6-minute data, hourly heights, high and low waters, and monthly means are

made available over the Web within one to four weeks after data collection. NWLON

data and accepted tidal datums are used in hydrographic surveys either to provide tide

reducers directly or for control for datum determination at subordinate (short-term)

stations. Preliminary and verified data are made available over the Web relative to

MLLW datum, station datum, or special water level datum (such as Columbia River

datum) as an user option in the interface.

Data Quality Monitoring

CO-OPS has an in-place Continuous Operational Real-Time Monitoring System (CORMS)

that provides quality control and system monitoring functions on a 24 hour/day, 7

days/week, all year around basis for CO-OPS monitored gauges. CORMS will monitor the status and performance of all in-house hydro gauges equipped with satellite

radios using the NOS satellite message format and that are installed by either CO-OPS,

NOAA Ships, Navigational Response Teams (NRT), or CO-OPS IDIQ contractors for NOAA

in-house hydro projects only, and once these gauges are listed on the hydro hot list by

CO-OPS, as it does for all other NOS water level systems, including all NWLON stations.

The CORMS system description can be found in System Development Plan, CORMS.

CORMS is a NOS provided support function to the operational field parties and does

not relieve the hydrographer of responsibility for performing QC and ensuring proper

gauge operation. As stated in Section 4.1.1, for NOAA hydrographic contract surveys,

the contractor is responsible for all data monitoring, repairs, and proper functioning of

the subordinate gauges.

7
4.1.5 General Data and Reference Datum Requirements

The present NOAA Nautical Chart Reference Datum for tidal waters is Mean Lower Low

Water (MLLW) based on the NOAA National Tidal Datum Epoch (NTDE) of 1983-2001 as

defined in the Tide and Current Glossary. All tidal datum computations and water level

reductions shall be referenced to this datum. In non-tidal areas, including the Great

Lakes, special low water datums have been defined for specific areas and are used as

chart datum in these locations. In some cases where historical sites are re-occupied,

site datum shall be zeroed to a pre-established MLLW datum held on a bench mark. In

that case, data can be acquired relative to MLLW for immediate application during the

survey. At present, in Great Lakes areas, a special Low Water Datum relative to IGLD

85 is the reference datum.

4.1.6 Error Budget Considerations

The water level reducers can be a significant corrector to soundings to reduce them

relative to chart datum especially in shallow water areas with relatively high ranges of

tide. The errors associated with water level reducers are generally not depth dependent, however. The portion of the error of the water level reducers must be balanced

against all other sounding errors to ensure that the total sounding error budget is not

exceeded. The allowable contribution of the error for tides and water levels to the total

survey error budget falls between 0.20 m and 0.45 m (at the 95% confidence level)

depending on the complexity of the tides.

The total error of the tides and water levels can be considered to have component

errors of:

1. The measurement error of the gauge/sensor and processing error to refer the measurements to station datum. Gauges/sensors need to be calibrated, and sensor

design and data sampling need to include strategies to reduce measurement errors due to waves, currents, temperature, and density effects. The measurements

need to be properly referenced to the bench marks and tide staffs, as appropriate and monitored for vertical stability. The measurement error, including the

dynamic effects, should not exceed 0.10 m at the 95% confidence level. The processing error also includes interpolation error of the water level at the exact time

of the soundings. An estimate for a typical processing error is 0.10 m at the 95%

confidence level.

2. The error in computation of tidal datums for the adjustment to an equivalent 19-

year National Tidal Datum Epoch (NTDE) periods for short term stations. The

shorter the time series, the less accurate the datum, i.e. bigger the error. An

inappropriate control station also decreases accuracy. The NTDE does not apply in

the Great Lakes, however the accuracy of datum based on shorter time series is

analogous. The estimated error of an adjusted tidal datum based on one month of

data is 0.08 m for the east and west coasts and 0.11 m for the Gulf coast (at the

95% confidence level).

3. The error in application of tidal zoning. Tidal zoning is the extrapolation and/or

interpolation of tidal characteristics from a known shore point(s) to a desired survey area using time differences and range ratios. The greater the extrapolation/interpolation, the greater the uncertainty and error. Estimates for typical errors associated with tidal zoning are 0.20 m at the 95% confidence level. However,

8
errors for this component can easily exceed 0.20 m if tidal characteristics are very

complex, or not well-defined, and if there are pronounced differential effects of

meteorology on the water levels across the survey area.

Project planning by NOS attempts to minimize and balance these potential sources of

errors through the use and specification of accurate reliable water level gauges, and

optimization of the mix of zoning required, the number of station locations required,

and the length of observations required within practical limits of the survey area and

survey duration. The practical limits depend upon the tidal characteristics of the area

and suitability of the coastline for the installation and operation of appropriate water

level stations.

4.2 Data Collection and Field Work

The hydrographer shall collect continuous and valid data series. Accurate datums cannot be computed for a month of data with a break in the water level measurement

series in excess of three days. Even breaks of significantly less than three days duration will not allow for interpolation during times when strong meteorological conditions

are present and in areas with little periodic tidal influence. Any break in the water

level measurement series affects the accuracy of datum computations. Breaks in data

also result in increased error in the tide reducers when interpolation is required to provide data at the time of soundings. At a critical measurement site where the water

level measurement data cannot be transmitted or monitored during hydrographic operations, an independent backup sensor or a complete redundant water level collection

system shall be installed and operated during the project.

4.2.1 Water Level Station Requirements

Data from NOS National Water Level Observation Network (NWLON) stations will be

provided to support hydrographic survey operations where appropriate. Data provided

are relative to Chart Datum which is Mean Lower Low Water for the 19-year National

Tidal Datum Epoch (NTDE).

The acquisition of water level data from subordinate locations may be required for hydrographic surveys and if so shall be specified by NOS in each individual set of Project

Instructions or Statement of Work. These stations shall be used to provide 6-minute

time series data, tidal datum references and tidal zoning which all factor into the production of final tide reducers for specific survey areas. Station locations and requirements may be modified after station reconnaissance or as survey operations progress.

Any changes shall be made only after consultation between the CO-OPS and the hydrographer (and COTR if contract survey) as moving required stations to new locations

may require new seven-digit station identifier numbers and new/historical station and

bench mark information.

The duration of continuous data acquisition shall be a 30-day minimum except for zoning stations. Data acquisition shall be from at least 4 hours before the beginning of

the hydrographic survey operations to 4 hours after the ending of hydrographic survey

operations, and/or shoreline verification in the applicable areas. Stations identified as

“30-day” stations are the “main” subordinate stations for datum establishment, providing tide reducers for a given project and for harmonic analysis from which harmonic

9
constants for tide prediction can be derived. At these stations, data must be collected

throughout the entire survey period in specified areas for which they are required, and

not less than 30 continuous days are required for accurate datum determination. Additionally, supplemental and/or back-up gauges may also be necessary based upon the

complexity of the hydrodynamics and/or the severity of environmental conditions of the

project area.

In non-tidal areas the correctors for hydrographic soundings are simply water level

measurements relative to a specified local low water level datum established for navigational purposes. Laguna Madre and parts of Pamlico Sound are examples of such areas classified as non-tidal which have special low water datums. Some river areas also

have special datums due to the effects of seasonal changes on the river, e.g., Columbia

River Datum, Hudson River datum, and Mississippi River Low Water are examples of

this case. Great Lakes NWLON permanent stations will provide water level data referenced to an established Low Water Datum relative to International Great Lakes Datum

of 1985 (IGLD 85).

4.2.2 Water Level Measurement Systems and Data Transmissions

Water Level Sensor and Data Collection Platform

The water level sensor shall be a self-calibrating air acoustic, pressure (vented), or

other suitable type that is approved by CO-OPS. The sensor measurement range shall

be greater than the expected range of water level. Gauge/sensor systems shall be

calibrated prior to deployment, and the calibration shall be checked after removal from

operations. The calibration standard’s accuracy must be traceable to National Institute

of Standards and technology (NIST). The required water level sensor resolution is a

function of the tidal range of the area in which hydrographic surveys are planned. For

tidal range less than or equal to 5 m, the required water level sensor resolution shall be

1 mm or better; for tidal range between 5 m and 10 m, the required water level sensor

resolution shall be 3 mm or better; and for tidal range greater than 10 m, the required

water level sensor resolution shall be 5 mm or better.

The Data Collection Platform (DCP) shall acquire and store water level measurements

at every 6- minutes. The water level measurements shall consist of an average of

at least three minutes of discrete water level samples with the period of the average

centered about the six minute mark (i.e. :00, :06, :12, etc.). In addition to the average measurement, the standard deviation of the discrete water level samples which

comprise the 6-minute measurements shall be computed and stored. The 6-minute

centered average water level data is required for compatibility with the NWLON stations, and the standard deviation provides valuable data quality information regarding

each measurement. The clock accuracy of a satellite radio system shall be within 5

seconds per month so that channel “stepping” does not occur. Non-satellite radio systems shall have a clock accuracy of within one minute per month. Known error sources

for each sensor shall be handled appropriately through ancillary measurements and/or

correction algorithms. Examples of such errors are water density variations for pressure gauges, sound path air temperature differences for acoustic systems, and high

frequency wave action and high velocity currents for all sensor types.

The NOS is currently using the Aquatrak® self-calibrating air acoustic sensors at the

majority of the NWLON stations. (For further information refer to Next Generation Water

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level Measurement System (NGWLMS) Site Design, Preparation, and Installation Manual, NOAA/NOS, January 1991 and User’s Guide for 8200 Acoustic Gauges, NOAA/NOS,

Updated August 1998). At stations where the acoustic sensor can not be used due to

freezing or the lack of a suitable structure, either a ParoScientific intelligent pressure

(vented) sensor incorporated into a gas purge system, or a well/float with absolute shaft

angle encoder (Great Lakes Stations) are used for water level measurements. (For further information refer to User’s Guide for 8200 Acoustic Gauges, NOAA/NOS, Updated

February 1998).

In each and any case, the water leveling sampling/averaging scheme shall be as described above. For short term subordinate stations which are installed to support NOS

hydrographic surveys, the use of air acoustic sensor is preferred over pressure sensor

whenever possible. Where the air acoustic sensor can not be installed, NOS uses a

vented strain gauge pressure sensor in a bubbler configuration (Refer to User’s Guide

for 8200 Acoustic Gauges, NOAA/NOS, updated February 1998). When using the vented

pressure sensor, a series of gauge/staff comparisons through a significant portion of a

tidal cycle shall be required (1) at the start, (2) at frequent intervals during deployment, and (3) at the end of a deployment. Frequent gauge/staff comparisons (at least

two times per week or minimum eight times per month) during deployment shall be

required to assist in assuring measurement stability and minimizing processing type

errors. The staff to gauge observations shall be at least three hours long at the beginning and end of deployment and the periodic observations during deployment shall be

1 hour long. The staff-to-gauge comparison criteria are general requirements. When

these staff-to-gauge observation frequency or time requirements cannot be met, then

refer to section 4.2.4. Staff observations for further information. Along with the averaging procedure described above which works as a digital filter, NOS uses a combination

protective well/parallel plate assembly on the acoustic sensor and a parallel plate assembly (with 2" orifice chamber) on the bubbler orifice sensor to minimize systematic

measurement errors due to wave effects and current effects, as shown in Figure 4.1.

When pressure sensors are used to collect the water level data, orifice should be

mounted on vertical surface such as piling of a wharf so that precise elevation of orifice below a staff stop could be measured with a steel tape, and the elevation of the

staff stop can be measured via differential leveling to the nearest benchmark and with

the primary bench mark. If the orifice is mounted vertically and its elevation can be

determined precisely with reference to the primary bench mark, then staff to gauge

readings may not be necessary, and the requirement for staff-to-gauge readings may

be waived (e.g. in seawater). If the orifice can not be mounted to a vertical surface i.e.

if the elevation of the orifice can not be determined precisely with the primary bench

mark, then staff-to-gauge readings are required to relate the water level datums to

the bench marks. Refer to additional information about staff and staff observations in

section 4.2.4.

Data Transmissions

The Data Transmissions requirements are applicable where CO-OPS is monitoring the

gauges as described in Section 4.1.4 above. The ability to monitor water level measurement system performance for near real-time quality assurance is essential to properly

support hydrographic survey operations. Therefore, it is required that, where access

to the satellite is available, the measurement system shall be equipped with a GOES

transmitter to telemeter the data to NOS every three hours or hourly. The data transmissions must use a message format identical to the format as currently implemented

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in NOS’ Next Generation Water Level Measurement Systems (NGWLMS). This is required

to assure direct compatibility with the NOS Data Management System (DMS). This data

format is detailed in the reference document “NGWLMS GOES MESSAGE FORMATTING”

(refer to Section 4.7 for References). Once station and gauge information is configured in DMS and station listed on the Hydro Hot List (HHL), the NOS Continuous Operational Real-Time System (CORMS) will monitor all water level measurement system

GOES transmissions to assure they are operating properly, provided that the GOES data

transmitted is compatible with NOS format. Data that is not transmitted by GOES, or

data transmitted but not in NOS compatible GOES format, or is submitted to CO-OPS

on electronic formats currently used such as, CD-ROM, DVD-ROM or such other digital

media, must also conform to the format specified in the above document so that data

can be loaded properly into DMS software. Refer to Section 4.6.3 for further details

about the water level data format specifications.

Close coordination is required between hydrographer and Requirements and Development Division (RDD) of CO-OPS for all hydrographic water level installations with satellite transmission capability. NOS will assist in acquiring assigned platform ID’s, time

slots, etc. At least three business days prior to the initiation of GOES data transmission

in the field, information about the station number, station name, latitude, longitude,

platform-ID, transmit time, channel, and serial numbers of sensors, and DCP shall be

faxed, phoned, or sent to RDD. Test transmissions conducted on site are outside this

requirement. This station and DCP information must be configured in DMS before data

transmissions begin so that the data will be accepted in DMS. The documentation required prior to transmission in field is defined in the NGWLMS Site Report, Field Tide

Note, or Water Level Station Report, as appropriate. (Refer to Section 4.6 Data Submission Requirements).

4.2.3 Station Installation, Operation and Removal

Hydrographers shall obtain all required permits and permissions for installation of the

water level sensor(s), Data Collection Platforms (DCP), bench marks, and utilities, as required. The hydrographer shall be responsible for security and/or protective measures,

as required. The hydrographer shall install all components in the manner prescribed

by manufacturer, or installation manuals. The hydrographer or contractor shall provide

CO-OPS of the position of all tide gauges installed before hydrography begins, including those that were not specified in the Statement of Work or Project Instructions, as

appropriate. The positions of bench marks and stations installed or recovered shall be

obtained as latitudes and longitudes (degrees, minutes, and tenth of seconds).

Water level station and its various components (tide house, Data Collection Platform,

all sensors, bench marks, and pertinent access facilities such as railings, steps, etc.,

as appropriate), when designed or installed by contractors, shall be installed and maintained as prescribed by manufacturers, installation manuals, appropriate local building

codes, or as specified by the Contracting Officer’s Technical Representative (COTR), if

applicable. Water level station and all installed components shall be structurally sound,

secure, and safe to use for NOS, local partners, and general public, as appropriate.

The following paragraphs provide general information regarding requirements for station installation, operations and maintenance, and station removal.

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Station Installation

A complete water level measurement gauge installation shall consist of the following:

• The installation of the water level measurement system (water level sensor(s),

DCP, and satellite transmitter) and its supporting structure and a tide staff if required.

• The recovery and/or installation of a minimum number of bench marks and a level

connection between the bench marks and the water level sensor(s), and tide staff

as appropriate.

• The preparation of all documentation and forms.

Operation and Maintenance

When GOES telemetry and NOS satellite message format is used, the hydrographer

shall monitor the near-real time water level gauge data daily for indications of sensor

malfunction or failure, and for other causes of degraded or invalid data, such as marine

fouling. This monitoring can be performed by accessing the COOPS web page (http:

//www.TidesandCurrents.noaa.gov). The data over this system are typically available for

review within three to four hours after collection.

All repairs, adjustments, replacements, cleaning, or other actions potentially affecting

sensor output or collection of data shall be documented in writing using appropriate

maintenance forms (see section on water level station documentation below) and retained as part of the water level data record. This documentation shall include, but

not be limited to, the following information: date and time of start and completion of

the maintenance activity; date and time of adjustments in sensor/DCP, datum offset, or

time; personnel conducting the work; parts or components replaced; component serial

numbers; tests performed; etc.

Removal

A complete removal of the water level measurement gauge shall consist of the following:

• Closing levels - a level connection between the minimum number bench marks

and the water level sensor(s) and tide staff as appropriate.

• Removal of the water level measurement system and restoration of the premises,

reasonable wear and tear accepted.

• The preparation of all documentation, forms, data, and reports.

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4.2.4 Tide Staffs

Staff

The hydrographer shall install a tide staff at a station if the reference measurement

point of a sensor (zero of a gauge) cannot be directly leveled to the local bench marks,

e.g. orifice is laid over sea floor in case of pressure based bubbler gauges. Even if a

pressure gauge can be leveled directly, staff readings are still required for assessment

of variations in gauge performance due to density variations in the water column over

time. The tide staff shall be mounted independent of the water level sensor so that

stability of the staff or sensor is maintained. Staff shall not be mounted to the same pile

on which the water level sensor is located. The staff shall be plumb. When two or more

staff scales are joined to form a long staff, the hydrographer shall take extra care to

ensure the accuracy of the staff throughout its length. The distance between staff zero

and the rod stop shall be measured before the staff is installed and after it is removed

and the rod stop above staff zero height shall be reported on the documentation forms.

In areas of large tidal range and long sloping beaches (i.e. Cook Inlet and the Gulf of

Maine), the installation and maintenance of tide staffs can be extremely difficult and

costly. In these cases, the physical installation of a tide staff(s) may be substituted by

systematic leveling to the water’s edge from the closest bench mark. The bench mark

becomes the “staff stop” and the elevation difference to the water’s edge becomes the

“staff reading”.

Staff Observations

When using the vented pressure sensor, a series of gauge/staff comparisons through

a significant portion of a tidal cycle shall be required (1) at the start of water level

data collection, (2) at frequent intervals during deployment, and (3) at the end of a deployment before gauge has been removed. Frequent gauge/staff comparisons during

deployment shall be required to assist in assuring measurement stability and minimizing processing type errors. The staff to gauge observations at the start and end of

deployment shall be at least each three hours long and the periodic observations during the deployment shall be at least 1 hour long. The staff to gauge observations shall

be performed three times per week, during each week of the project, with at least an

hour long observations of 6 minute interval for each time. Where staff to gauge observations can not be performed three times a week as required then an explanation is

required for the deficiency of number of observations and staff to gauge observations

shall be performed at least (a) minimum eight times spread out over each month (e.g.

two times per week) and at each time at least 1 hour of observations at 6 minute interval, or (b) minimum of four times spread out over each month (e.g. one time per

week) and at each time at least 2 hours of observations at 6 minute interval, whichever

is convenient.

The staff-to-gauge differences should remain constant throughout the set of observations and show no increasing or decreasing trends. After the water level data has

been collected, the averaged staff-to-gauge shall be applied to water level measurements to relate the data to staff zero. A higher number of independent staff readings

decrease the uncertainty in transferring the measurements to station datum and the

bench marks. Refer to Figure 4.2 for an example pressure tide gauge record.

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If the old staff is found destroyed by elements during the deployment, then a new staff

shall be installed for the remainder period of the deployment and a new staff to gauge

constant needs to be derived by new sets of staff to gauge observations. Also when a

staff or an orifice is replaced or re-established, check levels shall be run to minimum of

three bench marks including the PBM. Refer to Section 4.2.5 for leveling frequency and

other leveling requirements.

For water level historic stations that are reoccupied, NOS CO-OPS will provide the station datum (SD) information for the station. This information is generally given about

the Primary Bench Mark (PBM) above the historic SD. In that case, for pressure sensors

that require staff-to-gauge observations, all the water level data shall be placed on the

station datum using the following equation:

Water level data on the SD = (Preliminary pressure water level data on an arbitrary

datum as collected by the gauge) + (PBM above SD) - (Staff zero below PBM) - (weighted

staff-to-gauge constant)

Staff zero below PBM = (Staff stop below PBM) + (Staff zero below Staff stop)

The staff-to-gauge constant shall be derived as a weighted average of all the staff-togauge readings done for the project. The staff zero below PBM is obtained generally by

(a) leveling from PBM to staff stop and (b) then measuring the staff stop to staff zero

elevation with a steel tape and (c) then combining the two (a and b) elevation values.

The staff zero below PBM is obtained by averaging the elevations differences during the

opening (installation) and closing (removal) leveling runs for short term occupations.

The orifice elevation above station datum is also defined as accepted orifice offset in

CO-OPS Data Management System (DMS).

Bubbler Orifice and Parallel Plate Assembly

This bottom assembly is made of red brass, its chemical properties prevent the growth

of marine life by the slowly releasing copper oxide on its metal surface. A Swagelok®

hose fitting is screwed into the top end cap and is used to discharge the Nitrogen gas.

The Nitrogen gas flows through the bottom of the orifice at a rate sufficient to overcome

the rate of tidal change and wave height. This opening establishes the reference point

for tidal measurements. The parallel plates produce a laminar flow across the orifice to

prevent venturi effect. A two inch by eight inch pipe provides the correct volume gas

for widest range of surf conditions encountered by most coastal surveys.

15
Figure 4.1: Bubbler Orifice Bottom Assembly

16
Figure 4.2: Example - Pressure Tide Gauge Record

17
Pressure Tide Gauge Record

Station Name: Station No. (7 digit #):

Date Time Staff Reading Gauge/Staff Gas Pressure Wind Air

(M,D,Y) Gauge Correct High Low Difference Cyln Feed (Dir/Spd) Temp. Remarks

Table 1: Example Tide Gauge Record

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4.2.5 Bench Marks and Leveling

Bench Marks

A bench mark is a fixed physical object or marker (monumentation) set for stability

and used as a reference to the vertical and/or horizontal datums. Bench marks in

the vicinity of a water level measurement station are used as the reference for the

local tidal datums derived from the water level data. The relationship between the

bench marks and the water level sensor or tide staff shall be established by differential

leveling.

Number and Type of Bench Marks

The number and type of bench marks required depends on the duration of the water

level measurements. The User’s Guide for the Installation of Bench Marks and Leveling Requirements for Water Level Stations, dated October 1987, specifies the installation and documentation requirements for the bench marks. Each station will have one

bench mark designated as the primary bench mark (PBM), which shall be leveled to on

every run. The PBM is typically the most stable mark in close proximity to the water

level measurement station. The contractor shall select a PBM at sites where the PBM

has not already been designated. For historic NOS station reoccupations, CO-OPS will

furnish the designation/stamping of the PBM and PBM elevation above station datum,

as appropriate and if available.

The most desirable bench mark for GPS observations will have 360 degrees of horizontal clearance around the mark at 10 degrees and greater above the horizon and

stability code of A or B. Refer to Section 4.2.10 GPS Observations, and User’s Guide for

GPS Observations, Updated March 2007, for further information.

If the PBM is determined to be unstable, another mark shall be designated as PBM.

The date of change and the elevation difference between the old and new PBM shall

be documented. NOAA will furnish the individual NOS standard bench mark disks to

be installed. Bench mark descriptions shall be written according to User’s Guide for

Electronic Levels, updated January 2003.

Leveling

At least, geodetic third-order levels (refer to Reference 19, but 2nd order class I levels

are preferred) shall be run at short-term subordinate stations operated for less than

one-year. Requirements for higher order levels will be specified in individual project instructions, as appropriate. Standards and specifications for leveling are found in Standards and Specifications for Geodetic Control Networks and Geodetic Leveling (NOAA

Manual NOS NGS 3). Additional field requirements and procedures used by NOS for

leveling at tide stations can be found in the User’s Guide for the Installation of Bench

Marks and Leveling Requirements for Water Level Stations. Electronic digital/barcode

level systems are preferable. Specifications and standards for digital levels can be

found in Standards and Specifications for Geodetic Control Networks and additional

field requirements and procedures used by NOS for electronic leveling at water level

stations can be found in the User’s Guide for Electronic Levels, updated January 2003.

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Leveling Frequency

Levels shall be run between the water level sensor(s) or tide staff and the required number of bench marks when the water level measurement station is installed, modified

(e.g., water level sensor serviced, staff, or orifice replaced), for time series bracketing

purposes, or prior to removal. In any case, levels are required at a maximum interval

of six (6) months during the station’s operation, and are recommended after severe

storms, hurricanes, earthquakes to document stability (see stability discussed below).

Bracketing levels to appropriate number of marks (five for 30-day minimum stations)

are required (a) if smooth tides are required 30 days or more prior to the planned

removal of a applicable gauge(s), or (b) after 6 months for stations collecting data for

long term hydrographic projects.

Stability

If there is an unresolved movement of the water level sensor or tide staff zero relative

to the PBM, from one leveling to the next, of greater than 0.006 m, the hydrographer

shall verify the apparent movement by re-running the levels between the sensor zero

or tide staff to the PBM. This threshold of 0.006 m should not be confused with the

closure tolerances used for the order and class of leveling.

4.2.6 Water level Station Documentation

The field team shall maintain a documentation package for each water level measurement station installed for hydrographic projects. The documentation package shall be

forwarded to CO-OPS after a) installation of a station, b) performance of bracketing levels, c) gauge maintenance and repair, or d) removal of the station. Refer to time frames

for submission of documentation in Section 4.6.6.

Generally, all documentation (see Section 4.6 for Data Submission Requirements) shall

be forwarded to CO-OPS when a station is installed. For other situations, only information that has changed shall be submitted (e.g., levels and abstract for bracketing or

removal levels, NGWLMS Site Report for maintenance and repair or station removal,

etc.)

4.2.7 Additional Field Requirements

1. Generally upon completion of the data acquisition for each gauge installed, the

data must be sent as a batch for a 30-day minimum station unless the data are

transmitted via satellite. For long term station running more than three months,

the data shall be sent periodically (monthly) unless the data are transmitted via

satellite.

2. All water level data from a gauge shall be downloaded and backed up at least

weekly on electronic formats currently used such as CD-ROM or DVD-ROM, whether

the gauge data are sent via satellite or not.

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3. For new stations that do not have station numbers assigned, once the location of

the gauge has been finalized then contact CO-OPS and provide latitude and longitude of the gauge site at least three business days prior to actual installation of

the gauge in field. CO-OPS will assign a new station number within three business

days and inform the hydrographer.

4. The progress sketch shall show the field sheet, layout, area of hydrography, gauge

locations, and other information as appropriate. Verify the location of the gauge as

shown on the progress sketch, bench mark and tide station location sketch, field

tide note, Xpert Site report, NGWLMS Site Report or Tide station Report.

4.2.8 Geodetic Connections and Datums Relationship

Tidal datums are local vertical datums which may change considerably within a geographical area. A geodetic datum is a fixed plane of reference for vertical control of

land elevations. The North American Vertical Datum of 1988 (NAVD 88) is the accepted

geodetic reference datum of the National Geodetic Spatial Reference System and is

officially supported by the National Geodetic Survey (NGS) through a network of GPS

continuously operating reference stations. The relationship of tidal datums to NAVD

88 has many hydrographic, coastal mapping and engineering applications including

monitoring sea level change and the deployment of GPS electronic chart display and

information systems, etc.

Existing geodetic marks in the vicinity of a subordinate tidal station shall be searched

for and recovered. A search routine is available at http://www.ngs.noaa.gov. An orthometric level connection and ellipsoidal GPS tie is required at a subordinate tide station

which has geodetic bench marks located nearby as stated below for NAVD 88 Level Tie

and NAD 83 GPS Tie requirements. NAVD 88 heights for published bench marks are

given in Helmert orthometric height units by NGS. The GPS ellipsoid network height

accuracies are classified as conforming to 2 cm or 5 cm standards accuracies (Refer to

NOAA Technical Memorandum NOS NGS-58. At the present time, GPS ellipsoid heights

conforming to the 2 cm accuracy standards are required for contract hydrographic surveying projects. Refer to Section 4.2.10 GPS Observations and User’s Guide for Observations, NOAA/NOS, Updated March 2007.

A connection to the geodetic datums at a water level station enhances the value of the

tidal data, allowing comparison with other data sets. The geodetic network essentially

serves as a global reference datum to which all tidal datums can be referenced. The

connection to geodetic datums involves the following three ties:

1. NAVD 88 Level Tie

2. NAD 83 GPS Tie

3. NAVD 88 GPS Tie

4.2.9 NAVD 88 Level Tie

At all water level stations, a valid level tie to at least two Geodetic Bench Marks (GBM)

is required on each set of levels, where appropriate marks are available within 1.6 KM

21
(1 mi) leveling distance of the station location. A GBM is defined as a bench mark that

exists, is useable, is available in the NGS database, has a Permanent ID (PID), and has

a NAVD 88 elevation published on the datasheet.

At stations supporting hydro or other special projects, the tie shall be consistent with

the accuracy of the levels required for the project. Information on performing a valid

level tie is provided in the FGCC Standards and Specifications for Geodetic Control Networks, listed at the following website:

http://www.ngs.noaa.gov/FGCS/tech_pub/1984-stds-specs-geodetic-control-networks.htm#

3.5.

Also, Section 3.4 of Reference 2 User’s Guide for the Installation of Bench Marks and

Leveling Requirements for Water Level Stations provides information regarding how to

perform a valid level tie.

The Second Order, Class I tie is a requirement for digital levels to be accepted into the

NGS database. Since a level connection to GBMs with dynamic heights defines the IGLD

85 datum offset at each station in the Great Lakes, a valid connection to at least two

GBMs is required at each site in the Great Lakes.

A note shall be made in the remarks of the leveling section of the Tide Station Site

Report that a valid tie was achieved or not achieved. If a valid tie is not achieved, an

explanation shall be provided and/or recommendations made for making a valid tie in

the future.

If the water level station does not have two or more GBMs within 1.6 km (1 mi) leveling

distance of the station location, then the level tie requirement is waived.

4.2.10 GPS Observations

GPS observations are required to obtain elevation ties between the tidal datums and

GPS derived datums.

1. References and standards:

Static GPS observations shall be performed at water level stations in accordance

with Reference 8 “User’s Guide for GPS Observations”, NOAA/NOS Updated March

2007. Reference 20 “NOS NGS 58" provides further details. These guidelines

are written for establishing GPS derived ellipsoid height accuracy standards of 2

cm as outlined in NGS-58 document, for all survey projects, and special project

applications.

Static GPS surveys shall be conducted on a minimum of one bench mark at each

subordinate water level station installed/occupied for hydrographic or photogrammetric surveys.

Static GPS surveys shall be conducted at water level stations concurrently with

the occupation of NAVD 88 marks, if possible, to accomplish water level datum

transfers using GPS-derived orthometric heights.

22
2. Equipment and accuracies:

High accuracy static differential GPS surveys require a geodetic quality, dual frequency, full-wavelength GPS receiver with a minimum of 10 channels for tracking

GPS satellites.

A choke ring antenna is preferred, however, any geodetic quality ground plane antenna may be used. More important than antenna type, i.e. choke ring or ground

plane, is that the same antennas or identical antennas should be used during the

entire observing sessions. (If not, a correction for the difference in antenna phase

patterns (modeled phase patterns) must be applied.) This is extremely critical for

obtaining precise vertical results. The antenna cable length between the antenna

and receiver should be kept to a minimum when possible; 10 meters is the typical

antenna cable length. If a longer antenna cable is required, the cable must be

fabricated from low loss coaxial cable (RG233 for up to 30 meters and RG214 over

30 meters).

A fixed height precise GPS antenna tripod is required for this type of a survey. This

is a fixed height, 2 meter pole with three adjustable legs, a bull’s eye bubble to

plumb the antenna, and a magnetic compass to align the antenna to North. These

fixed height tripods reduce the chance of introducing an Height of Instrument (HI)

“blunder” during the post-processing of the data.

The manufacturer, model, and complete serial numbers of all receivers and antennas must be noted for each occupation on each station/bench mark observation

log sheet as shown in Figure 4.18.

3. Criteria for bench mark selection for GPS observations

The GPS Water Level Station Bench Mark (GPSBM) shall be selected based on the

following criteria: permanence or stability; historic GPS use; satellite visibility; and

safety and convenience.

• Permanence or stability of bench marks

NGS has defined the following monumentation quality codes, also called the

stability codes, for various bench mark settings.

Stability code A: monuments of the most reliable nature which may be expected to hold their elevations very well; e.g. Class A rod marks, or marks

installed on large boulders/rock outcrop.

Stability code B: monuments which probably hold their elevations well; e.g.

Class B rod marks, or marks installed on large concrete footings/foundations.

Stability code C: monuments which may hold their elevations but which are

commonly subject to surface ground movements; e.g. pavement or concrete

monuments.

Stability code D: movements of questionable or unknown reliability.

The station bench mark selected for GPS observations shall be of stability

code A or B. GPS observations on the primary bench mark (PBM) are preferred if the PBM is either stability code A or B, and is suitable for satellite

observations. Stability code C and D bench marks shall not be used for GPS

observations, unless NGS has previously made GPS observations on those

marks. Generally once a mark is selected for GPS observations, future GPS

observations shall be done on the same mark.

23
• Historic GPS use

In many states, CO-OPS has provided NGS with lists of selected marks suitable for GPS observations at water level stations, and NGS has completed

observations on these marks. Some tidal marks designated as Federal Base

Network (FBN) or Cooperative Base Network (CBN) marks may be of stability

code C. Generally once a mark is selected for GPS observations, future GPS

observations shall be done on the same mark. If leveling reveals instability of

the mark over time, select another mark.

Priority shall be given to a GBM for GPS observations because the GBM already

has a NSRS height (NAVD 88). The GBM considered here is one of the 10 tidal

or water level bench marks at a water level station.

• Satellite visibility

The most desirable bench mark for GPS observations should have 360 degrees clearance around the mark at 10 degrees and greater above the horizon. Newly established marks shall be set in locations that have these clearances, if at all possible. If a station does not have any marks suitable for GPS

observations, and it has been selected as needing GPS observations, a new

mark (stability A or B) shall be established. This new mark shall be connected

to the station bench mark network through conventional geodetic leveling,

and then GPS observations shall be made.

All existing station bench marks at operating stations shall be assessed for

feasibility of GPS observations, as time and resources permit. If electronic

leveling equipment is used, then a note shall be made, either in the APP field

of the electronic leveling HA file or on a copy of the published bench mark

sheet, stating the suitability of GPS observations for each mark. The GPS

visibility obstruction diagram shall also be completed for each mark observed.

GPS visibility obstruction diagram shall also be completed for each mark observed as shown in Figure 4.20.

• Safety and convenience

The location of the GPS bench mark should be safe, secure, and convenient.

Bench mark locations which allow unattended GPS data collection are desirable as the field crew can multi-task at the same time as collecting the GPS

data. The safety of the GPS equipment (vandalism proof) should be considered in the mark selection process.

The bench mark selected for GPS observations should be located on public

property rather than on private property, as permissions from private owners

may be required in the future to access the bench mark and for collecting the

GPS data. The distance from the station DCP should also be convenient.

4. Recording of data

Set the epoch update or recording interval (REC INT) for 15-seconds, which should

agree with the recording interval of the reference stations (IGS or CORS) used to

post-process the data. For GPS sessions greater than 30 minutes, collect data at

15-second epoch intervals, starting at an even minute. The elevation mask (ELEV

MASK) is typically set for 10 degrees for static surveys; low angle satellites can

degrade the final solution. Set the minimum number of satellites to four. For static

surveying, setting the minimum number of satellites (MIN SV) is not as critical as

for kinematic surveying. However, if the number of satellites tracked drops below

24
four, it could be an indication of other problems, such as an antenna or antenna

cable connection problem, RF interference, or an obstruction from traffic (vehicle

or vessel). The GPS signal from the satellite is not very strong when entering the

receiver, so anything that produces further attenuation of the signal can cause the

receiver to stop tracking satellites.

5. Position and photograph of the GPS bench mark

GPS (horizontal) positions (latitude and longitude) of each bench mark installed or

recovered shall be listed on the HA files for laser levels, if used, or on the bench

mark descriptions sheet for optical leveling, as applicable, at each subordinate

water level station occupied for hydrographic or photogrammetric surveys.

Digital photographs shall be taken of all station bench mark disks in accordance

with Reference 23 - Attachment R, Requirements for Digital Photographs of Survey

Control, NGS, July 2005”. A minimum of three photos shall be taken: close-up of

the disk face; chest or waist level view of the disk and setting; and horizontal

view of location and direction of view. The digital file for a bench mark photo shall

have the bench mark designation in its file name, followed by the view, with a jpg

extension, i.e. CONTAINER setting.jpg, or CONTAINER location NE.jpg.

A digital photo of the stamping of the bench mark occupied must be made as

shown in Figure 4.22. If digital photo is not available, then a rubbing of the bench

mark must be done as shown in Figure 4.21. A digital photo of the stamping is

preferred over rubbing of the mark.

Photos shall also be taken of station components such as protective wells, staffs,

tide house, DCPs, sensors, etc. One general location photo shall be taken showing

the water level station in relationship to its supporting structure and the local body

of water. All digital station photo files should be named such that the name of the

file will indicate the station number and the type of photo taken. For example,

the pressure sensor photo for DCP1 at San Francisco shall be named as 94142901

sensor N1.jpg.

6. Miscellaneous

Additional GPS suitable marks may be connected during the static survey using

rapid static GPS procedures to verify bench mark stability, if time and personnel

resources are available. Priority shall be given to connecting to the NSRS, particularly to the North American Vertical Datum of 1988 (NAVD 88) bench marks.

4.2.11 North American Datum (NAD 83) GPS Tie

The NGS Online Positioning User Service (OPUS) is now used extensively for quick and

convenient processing of the GPS raw data for a variety of applications. The position

solution provided by OPUS is considered preliminary data and is not retained by NGS.

Further information regarding using OPUS is provided in the next section.

The expected ellipsoid height accuracy for a 4 hour OPUS solution is 1.8 cm (at the 67%

confidence level), and that is desirable, practical, and achievable with the requirements

as specified in reference 20, NOAA Technical Memorandum NOS NGS-58, Guidelines for

Establishing GPS-Derived Ellipsoid Heights (Standards 2 cm and 5 cm), Version 4.3.

25
The length of GPS observation sessions depends upon the length of time the field crew

has available for GPS observations, security of the equipment, number of satellites

available at a site, number of GPS receivers available for GPS observations, etc.

For water level stations, collect a minimum of 4 hours of GPS data on the GPSBM. Extra

care shall be taken to ensure that the antenna height is precisely recorded, and that

the antenna setup is stable. A continuous long session (at least 4 hours long but less

than 24 hours) repeated annually is preferred to two or more shorter sessions (of less

than 4 hours each) repeated on the same visit, providing better data for OPUS and more

independent observations.

After the data collection session is complete, two independent downloads are required

from the GPS receiver to the laptop computer. If one downloaded file gets corrupted,

the other file may have good data. Do not make a copy of the downloaded file, as both

the files will have the same problem, if there is a problem. Follow the NGS guidelines for

naming these files. Submit both copies of the digital GPS data along with the necessary

documentation as specified in the User’s Guide for GPS Observations.

4.2.12 GPS Data Processing Using OPUS

Field parties shall use OPUS for processing the raw GPS observations. OPUS provides

an easily accessible, rapid method for submitting GPS data and receiving an almost

instantaneous solution response from NGS via email.

The NGS OPUS web page can be obtained at http://www.ngs.noaa.gov/OPUS/. The following information is found on the OPUS web page but is also presented here for convenience of the reader.

OPUS allows users to submit their GPS data files to NGS, where the data will be processed to determine a position using NGS computers and software. Each data file that

is submitted will be processed with respect to three CORS sites. The sites selected may

not be the nearest to your site but are selected by distance, number of observations,

site stability, etc. The position for your data will be reported back to you via email in

both ITRF and NAD 83 coordinates as well as Universal Transverse Mercator (UTM), U.

S. National Grid (USNG) and State Plane Coordinates (SPC) northing and easting.

OPUS is completely automatic and requires only a minimal amount of information from

the user:

1. The email address where you want the results sent.

2. The data file that you want to process (which you may select using the browse

feature; raw or RINEX accepted).

3. The antenna type used to collect this data file (selected from a list of calibrated

GPS antennas).

4. The height of the Antenna Reference Point (ARP) above the monument or mark

that you are positioning.

Once this information is complete, you then click the Upload button to send your data to

NGS. Your results will be emailed to you, usually within a few minutes. You may upload

26
multiple data files in a zip archive if you wish. However, be careful, the options that

you choose will be applied to all of the data files in that archive (i.e. the same antenna

type, ARP height will be used for all of the files in the zip file).

The following are some simple guidelines for analyzing the OPUS solutions.

1. Make sure the antenna type and the ARP height are correct.

2. Review the solution statistics:

(a) A good quality OPUS run should typically use 90% or more of your observations.

(b) OPUS should have fixed at least 80% of the ambiguities.

(c) The overall RMS should seldom exceed 3 cm.

(d) The maximum peak to peak errors should be less than 2 cm for horizontal and

4 cm for vertical (This depends, of course, on the accuracy you are trying to

achieve).

NGS needs to receive orbit data from IGS in order to obtain a solution. If the data is submitted too quickly, the submitter may need to re-submit the data at a later time. For

best results, submit the GPS data to OPUS at least 17 hours after the first midnight (in

Greenwich Mean Time) following the time when the observations were recorded. Compare the resultant solution to the last previous solution made at the station, if available,

to ensure that you do not have a blunder in the antenna setup. This will be revealed

by a noticeable discrepancy in the ellipsoid height. Include a copy of the solution in the

station inspection documentation package submitted to CO-OPS RDD/OET, as well as

the GPS data sets.

4.2.13 OPUS DB Preliminary Information

Pending NGS support, OPUS DB will be released by NGS. This advanced version of OPUS

will submit OPUS solutions directly to the NGS database if all required documentation is

provided by the submitter. Further guidance will be provided once OPUS DB is released

and these specifications will be updated as appropriate. Any data sets submitted to

OPUS and the results will be subsequently re-submitted by CO-OPS’ RDD/OET to OPUS

DB to ensure the data is published by NGS.

Height modernization guidelines are here: http://www.ngs.noaa.gov/heightmod/guidelines.

shtml

The Opus DB datasheet concept is fully listed at the following NGS web site: http:

//www.ngs.noaa.gov/PROJECTS/draft/OPUS/OPUS-DB-concept.htm

The following tables identify the required data elements and optional data elements for

OPUS DB

Respectively:

27
ELEMENT RATIONALE

e-mail For identification & correspondence

Filename Necessary to compute position

Antenna Necessary to compute position

Antenna height Necessary to compute position

Name of submitting agency Identifies the observer

Permanent Identifier (PID) Identifies the station

Designation Identifies the station

Descriptive text Aids in station recovery

Rod/pipe depth & units Describes monumentation quality

Sleeve depth & units Describes monumentation quality

Setting code & specific setting text Describe monumentation quality

Photograph (of marker) Aids in station recovery

Table 2: Required Data Elements (15 each)

ELEMENT RATIONALE

Photographs (of equipment, horizon) Equipment photos describe antenna height and

equipment used. Horizon photos aid in station

recovery and could explain visibility or multipath

problems.

Vertical stability code Useful for stability assessment.

Magnetic property code Aids in station recovery.

Antenna s/n Useful in identifying equipment-specific problems.

Receiver Useful in identifying equipment-specific problems.

Receiver s/n Useful in identifying equipment-specific problems.

Receiver firmware Useful in identifying firmware-specific problems.

Stamping Aids in station identification.

Condition code Useful for stability assessment.

Special application codes Identifies the station type (tidal station, Public

Land Survey corner, etc.)

Remarks Allows user to record observation comments.

Table 3: Optional Data Elements (11 each):

28
This information regarding the Required Data Elements and Optional Data Elements is

for reference only and not required at the present time. These requirements will be

active once OPUS DB is designated operational by NGS. Out of the 15 Required Data

Elements, 13 are applicable to all the marks and the remaining two - rod/pipe depth &

units and sleeve depth & units – are applicable only to rod marks.

4.2.14 NAVD 88 GPS Tie

The NAVD 88 GPS tie involves simultaneous GPS observations at the GPSBM and one

or more GBMs located up to 10 KM (6.26 mi) from the GPSBM. This “Height Mod” tie

is deferred until such time as NGS enables user-friendly bluebooking of campaign data

(OPUS projects).

4.3 Data Processing and Reduction

4.3.1 Data Quality Control

The required output product used in generation of tide reducers and for tidal datum

determination is a continuous time series of 6-minute interval water level data for the

desired time period of hydrography and for a specified minimum time period from which

to derive tidal datums. CO-OPS will monitor the installed system operation information

for all gauges equipped with GOES satellite radios. The 6-minute interval water level

data from the water level gauges shall be quality controlled to NOS standards by the

contractor for invalid and suspect data as a final review prior to product generation and

application. This includes checking for data gaps, data discontinuities, datum shifts,

anomalous data points, data points outside of expected tolerances such as expected

maximum and minimum values and for anomalous trends in the elevations due to sensor drift or vertical movement of the tide station components and bench marks.

Quality control shall include comparisons with simultaneous data from backup gauges,

predicted tides or data from nearby stations, as appropriate. Data editing and gap

filling shall use documented mathematically sound algorithms and procedures and an

audit trail shall be used to track all changes and edits to observed data. All inferred

data shall be appropriately flagged. Water level measurements from each station shall

be related to a single, common datum, referred to as Station Datum. Station Datum

is an arbitrary datum and should not be confused with a tidal datum such as MLLW. All

discontinuities, jumps, or other changes in the gauge record (refer to the specific gauge

user’s guide) that may be due to vertical movement of any the gauge, staff, or bench

marks shall be fully documented. All data shall be recorded on UTC and the units of

measurement shall be properly denoted on all hard-copy output and digital files. Refer

to Section 4.6 Data Submission Requirements for details.

4.3.2 Data Processing and Tabulation of the Tide

The continuous 6-minute interval water level data are used to generate the standard

tabulation output products. These products include the times and heights of the high

and low waters, hourly heights, maximum and minimum monthly water levels, and

29
monthly mean values for the desired parameters. Examples of these tabulation products are found in Figure 4.3 and 4.4 for tide stations and Figure 4.5 for Great Lakes

stations. The times and heights of the high and low waters shall be derived from appropriate curve-fitting of the 6-minute interval data. For purposes of tabulation of the high

and low tides and not non-tidal high frequency noise, successive high and low tides

shall not be tabulated unless they are greater than 2.0 hours apart in time and 0.030

meters different in elevation. Hourly heights shall be derived from every 6-minute value

observed on the hour. Monthly mean sea level and monthly mean water level shall be

computed from the average of the hourly heights over each calendar month of data.

Data shall be tabulated relative to a documented consistent station datum such as tide

staff zero, arbitrary station datum, MLLW, etc.. over the duration of the data observations. Descriptions of general procedures used in tabulation are also found in the Tide

and Current Glossary, Manual of Tide Observations, and Tidal Datum Planes.

4.3.3 Computation of Monthly Means

Monthly means are derived on a calendar month basis in accordance with the definitions for the monthly mean parameters as found in the Tide and Current Glossary.

Examples of the desired monthly means are found in 4.7. For purposes of monthly

mean computation, monthly means shall not be computed if gaps in data are greater

than three consecutive days. For partial months of data, tide by tide comparison with

the control station data shall be performed.

4.3.4 Data Editing and Gap Filling Specifications

When backup sensor data are not available, data gaps in 6-minute data shall not be

filled if the gaps are greater than three consecutive days in length. Data gap filling shall

use documented mathematically and scientifically sound algorithms and procedures

and an audit trail shall be used to track all gap-fills in observed data. Data gaps of

less than 3-hours can be inferred using interpolation and curve-fitting techniques. Data

gaps of longer than three hours shall use external data sources such as data from

a nearby station. All data derived through gap-filling procedures shall be marked as

inferred. Individual hourly heights, high and low waters, and daily means derived from

inferred data shall also be designated as inferred.

30
Figure 4.3: High and Low Water Data

31
Figure 4.4: Hourly Height Water Level Data for a Tide Station

32
Figure 4.5: Hourly Height Water Level Data for a Great Lakes Station

33
4.4 Computation of Tidal Datums and Water Level Datums

4.4.1 National Tidal Datum Epoch

Tidal datums must be computed relative to a specific 19 year tidal cycle adopted by

the National Ocean Service (NOS) called the National Tidal Datum Epoch (NTDE). The

present NTDE is the period 1983 through 2001. A primary datum determination is

based directly on the average of tide observations over the 19 year Epoch period at NOS

permanent long term primary control stations in the National Water Level Observation

Network (NWLON). The data from NOS primary stations are used to compute datums at

short term subordinate stations by reducing the data from those subordinate stations

to equivalent 19 year mean values through the method of comparison of simultaneous

observation.

4.4.2 Computational Procedures

The equivalent 19 year tidal datums for subordinate stations are computed for certain

phases of the tide using tide-by-tide comparisons or monthly mean comparisons with

an appropriate NOS long term control station. Accepted 19 year mean values of mean

tide level (MTL), mean range (Mn), diurnal high water inequality (DHQ), diurnal low water inequality (DLQ), diurnal tide level (DTL), and great diurnal range (Gt) are required

in the reduction process in which a “short series” of tide observations at any location

are compared with simultaneous observations from an NOS control station. Datums are

computed by the “standard” method of range ratio comparison generally on the West

coast and Pacific Islands where there exists a large diurnal inequality in the low and

high waters. The “modified” method of range ratio comparison is generally used on the

East coast and Caribbean where small differences exist in the low and high water diurnal inequalities. For stations requiring a datum determination, at least 30 continuous

days of tide observations are required for stations where adequate primary datum control exists. For error budget purposes, one month of data results in a datum accuracy of

0.11 m (95% confidence level) for Stations in the Gulf of Mexico and 0.08 m (95% confidence level) for east and West Coast stations. Examples of a tide by tide and a monthly

mean simultaneous comparison for datum determination are found in Figures 4.6 and

4.7. Descriptions of the tidal datum computational procedures are found in the Tide

and Current Glossary, Tidal Datum Planes, Manual of Tide Observations, NOAA Special Publication NOS CO-OPS 1Tidal Datums and Their Applications and Computational

Techniques for Tidal Datums.

4.4.3 Tidal Datum Recovery

Whenever tide stations are installed at historical sites, measures shall be taken to “recover” the established tidal datums through leveling which shall be accomplished by

referencing the gauge or tide staff zero “0" to more than one existing bench mark (three

bench marks are preferred) with a published tidal elevation. Through this process, the

published MLLW elevation is transferred by level differences to the “new” gauge or tide

staff and compared to the MLLW elevation computed from the new data on the same

zero “0". Factors affecting the datum recovery (i.e. differences between old and newly

computed datums) include the length of each data series used to compute the datums,

34
the geographical location, the tidal characteristics in the region, the length of time between reoccupations, the sea level trends in the region, and the control station used.

Based on all of these factors, the datum recovery can be expected to vary from +/-

0.03 m to +/- 0.08 m. Hence, this process also serves as a very useful quality control

procedure. After a successful datum recovery is performed and benchmark stability is

established, the historical value of Mean Lower Low Water (MLLW) shall be used as the

operational datum reference for data from the gauge during hydrographic survey operations. An example of a published tidal datum sheet for a station for which a datum

recovery could be made is found in Figure 4.8.

35
(a)

Figure 4.6: Tide-By-Tide Comparison

36
(b)

Figure 4.6: Tide-By-Tide Comparison (continued)

37
(c)

Figure 4.6: Tide-By-Tide Comparison (concluded)

38
(a)

Figure 4.7: Monthly Mean Simultaneous Comparison Example

39
(b)

Figure 4.7: Monthly Mean Simultaneous Comparison (continued)

40
(c)

Figure 4.7: Monthly Mean Simultaneous Comparison (concluded)

41
(a)

Figure 4.8: Published Bench Mark Sheet

42
(b)

Figure 4.8: Published Bench Mark Sheet (continued)

43
(c)

Figure 4.8: Published Bench Mark Sheet (continued)

44
(d)

Figure 4.8: Published Bench Mark Sheet (continued)

45
(e)

Figure 4.8: Published Bench Mark Sheet (continued)

46
(f)

Figure 4.8: Published Bench Mark Sheet (continued)

47
(g)

Figure 4.8: Published Bench Mark Sheet (continued)

48
(h)

Figure 4.8: Published Bench Mark Sheet (concluded)

49
4.4.4 Quality Control

It is essential for tidal datum quality control to have data processing and leveling procedures carried out to the fullest extent. Caution must also be used in computing tidal

datums in riverine systems or in regions of unknown tidal regimes. Tide-by-tide comparisons between subordinate and control station data will often detect anomalous differences which should be investigated for possible gauge malfunction or sensor movement. Datums shall be established from more than one bench mark. Differences in

elevations between bench marks based on new leveling must agree with previously

established differences from the published bench mark sheets. Any changes in the elevation differences must be reconciled before using in any datum recovery procedure.

Datum accuracy at a subordinate station depends on various factors, but availability

and choice of an adequate control station of similar tidal characteristics, similar daily

mean sea level and seasonal mean sea level variations, and similar sea level trends

are the most important. The length of series will also determine accuracy. The longer

the series, the more accurate the datum and the greater quality control and confidence

gained from analyzing numerous monthly mean differences between the subordinate

and control station. At reoccupied historical stations for which datum recoveries are

made, updated datums shall be computed from the new time series and compared

with the historical datums as the survey progresses.

4.5 Final Zoning and Tide Reducers

Data relative to MLLW from subordinate stations or from NWLON stations, as appropriate, shall be applied to reduce sounding data to chart datum, either directly or indirectly

through a correction technique referred to as tidal zoning. Whether corrected or direct,

time series data relative to MLLW or other applicable LWD applied to reference hydrographic soundings to chart datum are referred to as “tide reducers” or “water level

reducers”.

4.5.1 Water Level Station Summaries

Data are reduced to mean values and subsequently adjusted to National Tidal Datum

Epoch (NTDE) values for tidal datums and characteristic tidal attributes as prescribed

in Section 4.4 and 4.5. “Summary files” shall be created for each subordinate tide

station occupied for the survey. These summary data facilitate the development of

corange and cophase lines and final zoning schemes. They also provide input into the

NOS tidal datum bench mark publication process which supports navigation, boundary

and shoreline determination, coastal engineering and management. NTDE values for

Greenwich high and low water intervals, mean and diurnal ranges and high and low

water inequalities shall be tabulated in these summary files which also contain the

datums, the time and length of the series and NOS control station which was used

to compute 19-year equivalent NTDE values. NTDE datums shall be tabulated in the

summary file relative to a documented consistent station datum such as tide staff zero

or arbitrary station datum. The elevation of the primary bench mark shall be provided

in this summary relative to the same zero or station datum. Latitude and longitude

positions shall also be provided. An example of a summary file is provided in Figure 4.9.

Summary file data from new station occupations and NOS provided summaries from

historical occupation and control stations within the survey area shall be used as input

data to the tidal zoning process.

50
4.5.2 Construction of Final Tidal Zoning Schemes

As tidal characteristics vary spatially, data from deployed water level gauges may not

be representative of water levels across a survey area. Tidal zoning shall be implemented to facilitate the provision of time series water level data relative to chart datum for any point within the survey area such that prescribed accuracy requirements

are maintained for the water level measurement component of the hydrographic survey. NOS currently utilizes the “discrete tidal zoning” method for operations, where

survey areas are broken up into a scheme of zones bounding areas of common tidal

characteristics. The minimum requirement is for a new zone for every 0.06 m change

in mean range of tide and every 0.3 hour progression in time of tide (Greenwich high

and low water intervals). Phase and amplitude corrections for appropriate tide station

data shall be assigned to each zone.

As part of the process, tidal characteristics shall be accessed using geographic spatial

placement of summary data in a commercial GIS compatible format to assess spatial

variations in tidal characteristics. Corange and cophase maps shall be generated to

provide the base for development of zoning schemes. Preliminary zoning, which is

based on available historical tide station data and estuarine and global tide models,

is referenced to an applicable predictions reference station for utilization during field

work. For final processing, preliminary zoning shall be superseded by “final zoning”

which is a refinement based on new data collected at subordinate stations during the

survey. With the final zoning scheme, correctors for each zone shall be derived from a

subordinate station specifically installed for the survey rather than the reference station used with preliminary zoning. For contract surveys, the contractor shall develop

and utilize a zoning scheme to the specifications mentioned above such that water

level reducers are within required accuracy across the entire survey area. Zoning errors shall be minimized such that when combined with errors from actual water level

measurement at the gauge and errors in reduction to chart datum, the total error of

the tide reducers is within specified tolerances. The final zoning scheme and all data

utilized in its development shall be documented and submitted. Examples of zoning

files and graphics are provided in Figures 4.10, 4.11, 4.12, 4.13, and 4.15 .

4.5.3 Tide Reducer Files and Final Tide Note

Verified time series data collected at appropriate subordinate stations are referenced

to the NTDE Mean Lower Low Water (Chart Datum) through datum computation procedures outlined in Section 4.4. Time series data collected in six-minute intervals and

reduced to chart datum as specified, both from subordinate gauges operated by the

contractor and from NWLON stations where appropriate, shall be used either directly

or corrected through use of a zoning scheme as determined appropriate by the contractor such that tide reducers are within specified tolerances. A Final Tide Note shall

be submitted for each hydrographic sheet with information as to what final tidal zoning

should be applied to which stations to obtain the final tide reducers. An example Final

Tide Note and final tidal zoning graphic is found in Figure 4.15.

51
Figure 4.9: Tide Station Summary

52
Figure 4.10: GIS Summary Data File

53
Figure 4.11: Corange Line of Greenwich, High and Low Water Intervals (in hours)

54
Figure 4.12: Tidal Zoning for Approaches to Nikiski, Alaska

55
Figure 4.13: Example Tide Reducer File from NOAA Acoustic System

56
4.6 Data Submission Requirements

Data submission requirements for water level measurement stations are comprised of

both supporting documents for the installation, maintenance, and removal of stations,

and the formatted digital water level data collected by the water level measurement

system required for NOS quality control and ingestion into the NOS data base management system. In addition, documentation for processing and tabulation of the data,

tidal datum computation, and final tidal zoning are required.

Data submission requirements for GPS project consists of project reports, station (bench

mark) description or recovery notes, observation log sheets, station visibility diagrams,

photographs or rubbings of station marks, raw GPS data, RINEX GPS data, and other info

as pertinent.

4.6.1 Station Documentation

The documentation package shall be forwarded to CO-OPS after a) installation of a

station, b) performance of bracketing levels, c) gauge maintenance and repair, or d)

removal of the station. Refer to Section 4.6.6 for time frames for documentation submission requirements and Figure 4.14, Water Level Station Documentation Checkoff

List. The station documentation generally includes, but is not limited to the following:

1. Transmittal letter (PDF format).

2. Field Tide Note (PDF format), if applicable.

3. Calibration test documentation from an independent source other than the manufacturer for each sensor used to collect water level or ancillary data. (PDF format).

4. E-Site Report, Water Level Station Xpert Site Report, or Tide Station Report (NOAA

Form 77-12), or equivalent. (E-Site report application is in web based electronic

format, Water Level Station Xpert Site Report or Tide Station report in Microsoft Excel format). Contractor created Site Reports are acceptable as long as the reports

provide same required information.

5. Google Chartlet, or NOAA Chartlet with chart number or map name and scale

shown including standard NOS title block (JPEG and PDF format).

6. U.S. Geological Survey quadrangle map (7.5 minutes map) indicating the exact

location of the station, with map name and scale shown (JPEG and PDF format).

7. Sensor test worksheet (JPEG and PDF format) (applicable for acoustic gauges).

8. Sensor elevation drawing (JPEG and PDF format) showing sea floor, pier elevation,

and sensor elevation if sensor is mounted vertically.

9. Water level transfer form (applicable for Great Lakes stations only, in JPEG and PDF

format).

10. Large-scale bench mark location sketch of the station site showing the relative location of the water level gauge, staff (if any), bench marks, and major reference

objects found in the bench mark descriptions. The bench mark sketch shall include an arrow indicating north direction, a title block, and latitude and longitude

(derived from handheld GPS) of the gauge (JPEG and PDF format).

57
11. New or updated description of how to reach the station from a major geographical

landmark (in Microsoft Word and PDF format). (Refer to User’s Guide for Writing

Bench Mark Descriptions, NOAA/NOS, Updated January 2003).

12. Bench mark descriptions with handheld GPS coordinates (in Microsoft Word and

JPEG format) (Refer to User’s Guide for Writing Bench Mark Descriptions, NOAA/NOS,

Updated January 2003).

13. Digital photographs of bench mark disk faces, setting, bench mark locations from

two different (perpendicular) cardinal directions, station, DCP, equipment, underwater components, and vicinity (JPEG and PDF format). As a minimum, photographs shall show a view of the water level measurement system as installed,

including sensors and DCP; a front view of the staff (if any); multiple views of

the surroundings and other views necessary to document the location; and photographs of each bench mark, including a location view and a close-up view showing the bench mark disk (face) stamping. Bench mark photo file names start with

mark designation followed by either “face” or “location” and direction of view,

with jpg extension (e.g. 8661070 B location south.jpg). All other station component photo file names start with station number and view name (e.g. 8661070

tide station view south).

14. Level records (raw levels) including level equipment information (electronic files)

and field notes of precise leveling, if applicable.

15. Level abstract (electronic file for optical and barcode levels).

16. Datum offset computation worksheet or Staff/Gauge difference work sheet as

appropriate showing how sensor “zero” measurement point is referenced to the

bench marks.

17. Calibration certificates for Invar leveling rods, if applicable (in PDF format).

18. Staff to gauge observations, if applicable (in Microsoft Excel and PDF format).

19. Agreements, MOU, contract documents, utilities/pier agreements, etc., if applicable (in PDF format).

20. Other information as appropriate, or as specified in the contract (in PDF format).

21. Water level data download.

22. GPS Project report, GPS observations in raw and RINEX format, GPS observations

log sheets, antenna height measurements, visibility diagrams, OPUS results, as

required GPS documentation, if applicable, (all in various electronic format). The

GPS documentation requirements are described in detail in the next Section 4.6.2.

4.6.2 GPS Project Documentation

The following information in addition to the results obtained from OPUS shall be submitted to CO-OPS at the end of the project (see the time frames for submission of GPS

data later in Section 4.6.6) so that proper information can be forwarded to NGS for

blue-booking purposes.

This documentation is important because most of the information is used to submit the

GPS data to NGS. In addition to the log, data must comply with the “Data Submission

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to NGS Section” of NGS-58 and the “Input Formats and Specifications of the National

Geodetic Survey (NGS) Data Base” to become part of the NSRS.

GPS data collected by contractors or NOAA Ships for hydrographic survey support, or

special projects shall be processed by the parties, and final data product - Receiver

Independent Exchange Format (RINEX) data and appropriate forms - shall be submitted

to CO-OPS which will be forwarded to NGS, as per the contracts, project instructions,

Statement of Work, or as appropriate.

GPS forms in PDF format can be found at the following NGS Federal Base Network web

site: http://www.ngs.noaa.gov/PROJECTS/FBN/index.htm

Refer to Figure 4.16 through Figure 4.22 for GPS projects submission checklist and sample package contents.

• Project report (Refer to Figure 4.16): One project report per GPS project is required.

• Station (bench mark) description or recovery notes (Refer to Figure 4.17): One per

bench mark, for which GPS observations are submitted, is required.

• Observation log sheets (Refer to Figure 4.18 and Figure 4.19): One per each GPS

observation session is required.

• Station/bench mark visibility diagrams (Refer to Figure 4.20): One per each bench

mark, for which GPS observations are submitted, is required.

• Photographs or rubbings of station (bench) marks (Refer to Figure 4.22 and Figure 4.21): One per each bench mark, for which GPS observations are submitted,

is required.

• Raw GPS data

• RINEX GPS data

• OPUS results

59
(a)

Figure 4.14: Project Documentation and Data Checkoff List

60
(b)

Figure 4.14: Project Documentation and Data Checkoff List (continued)

61
(c)

Figure 4.14: Project Documentation and Data Checkoff List (continued)

62
(d)

Figure 4.14: Project Documentation and Data Checkoff List (concluded)

63
(a)

Figure 4.15: Final Tide Note and Final Tidal Zoning Chart

64
(b)

Figure 4.15: Final Tide Note and Final Tidal Zoning Chart (continued)

However, analyses also show that there are several geographic areas whose sea level

trends are strongly anomalous from the average trends found across the NWLON and

thus, must be treated differently. One of these areas is in Cook Inlet, Alaska. Nikiski

has shown a significant relative sea level change due to continued vertical land movement after the 1964 earthquake. NOS has adopted a procedure for computing accepted

tidal datums for this anomalous region by using an MSL value calculated from the last

several years of data rather than the 19-year NTDE. The accepted range of tide is still

based on the 19-year NTDE and, when applied to the updated MSL, will result in updated values for Mean High Water (MHW) and Mean Lower Low Water (MLLW) derived

through standard datum calculation procedures. For Nikiski, the MSL value was computed from the period of 1994-1998. This resulted in a lowering of the MLLW datums

relative to land by approximately 1.0 ft at Nikiski compared to the previous MLLW elevations used in surveys prior to January 1, 1998. Subordinate tide stations in the area

used for hydrographic surveys and controlled by Nikiski will be affected similarly. Accepted datums have been computed and may be accessed on the Internet through the

URL specification http://www.tidesandcurrents.noaa.gov.

65
Figure 4.16: Project Submission Checklist

66
(a)

Figure 4.17: Station Descriptive - Recovery Form

67
(b)

Figure 4.17: Station Descriptive - Recovery Form (continued)

68
Figure 4.18: GPS Station Observation Log

69
Figure 4.19: GPS Antenna Height Measurements

70
Figure 4.20: GPS Visibility Obstruction Diagram

71
Figure 4.21: Station Pencil Rubbing Form

72
Figure 4.22: Digital Photo of Stamping of Bench Mark

4.6.3 Water Level Data

The final observed water level measurements shall be reported as heights in meters to

three decimal places (i.e. 0.001 m). All heights shall be referenced to station datum and

shall be referenced to UTC. The final tide reducer time series data shall be referenced

to MLLW and shall be referenced to UTC. The contractor shall provide the water level

data in the format specified below from the water level gauges installed.

The original raw water level data and also the correctors used to convert the data to

chart datum shall be retained until notified in writing or at least two years after the

survey is completed. All algorithms and conversions used to provide correctors shall

be fully supported by the calibrations, maintenance documentation, leveling records,

and sound engineering/oceanographic practices. Sensors for measurements used to

convert data (e.g. pressure to heights) shall be calibrated and maintained for the entire

water level collection period.

All digital water level and ancillary data shall be transmitted to CO-OPS in a format

dependent on the DCP configuration. If GOES satellite is used, the data shall be transmitted and received using the NOS compressed pseudo binary format (see NGWLMS

GOES Message Formatting, Libraro, 1/2003). These satellite messages are then decoded by NOS DMS upon receipt from NESDIS before further processing and review by

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CORMS can be completed. If satellite transmission configurations cannot be installed,

the data shall be manually downloaded from the DCP and submitted to NOS, as shown

in the format below, in a digital format, on CD-ROM, or by email as an ASCII data attachment. It may be prudent to submit data at more frequent intervals under specific

circumstances.

Data download files shall be named in the following format: xxxxxxxy.w1.DAT, where

xxxxxxx is the seven digit station number, y is the DCP number (usually 1), w1 is the

product code for 6-minute data, and DAT is the extension (Use T = 2,3...if more than

one file is from the same station and DCP). This is the format needed when the data

is loaded into DMS. Also each water level data file (XXX.BWL or XXX.ACO) shall have

only 3 months of data. If the water level station was operational for more than three

months, please submit multiple xxxxxxxy.DAT files, each file with only three months of

data.

Multiple DCP may have been used to collect 6-minute water level data for a particular

site, and backup or redundant DCP data may be used to fill the gap in the primary DCP

data,. but, water level data shall be submitted for single DCP (numbered as 1). All the

water level data shall be on station datum.

Each input record (including the final record) ends with a carriage return and excludes

any extraneous characters such as trailing blank spaces for all types of water level

data (6-minute water level data, hourly height, high/low, monthly means, and station

datum).

The 6-minute interval data (acoustic sensor and pressure sensor examples follow) shall

have the following format for CO-OPS database to accept.

Acoustic Sensor Data (XXX.ACO format)

Column 1- 7 Station ID (7 digits, assigned in the project instructions)

Column 8- 8 1 (DCP number, use 2, 3 , etc., for additional DCPs)

Column 9-19 Date (MMM DD YYYY format, e.g. JAN 01 1998)

Column 20-20 Blank

Column 21-22 Hours in 24 hour format (i.e. 00, 01, ...., 23)

Column 23-23 : (colon)

Column 24-25 Minutes (00,06,12, ..., 54)

Column 26-32 Data value in millimeters, right justified, (e.g. 1138)

Column 33-38 Sigma (standard deviation in millimeters in integer format)

Column 39-44 Outlier (integer format)

Column 45-50 Temperature 1 (tenth of degrees C in integer format)

Column 51-56 Temperature 2 (tenth of degrees C in integer format)

Column 57-58 Sensor type (A1 for acoustic type)

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Column 59-60 blank

Column 61-61 Data Source (S for Satellite, D for Diskette)

Sample data:

85169901AUG 17 2007 05:00 1138 23 0 308 297A1 D

85169901AUG 17 2007 05:06 1126 26 0 308 298A1 D

85169901AUG 17 2007 05:12 1107 26 1 309 298A1 D

Pressure Sensor or Generic Data (XXX.BWL format)

Column 1- 7 Station ID (7 digits, assigned in the project instructions)

Column 8- 8 1 (DCP number, use 2, 3 , etc., for additional DCPs)

Column 9-19 Date (MMM DD YYYY format, e.g. JAN 01 1998)

Column 20-20 Blank

Column 21-22 Hours in 24 hour format (i.e. 00, 01, ..., 23)

Column 23-23 : (colon)

Column 24-25 Minutes (00-54)

Column 26-32 Data value in millimeters, right justified, (e.g. 1138)

Column 33-38 Sigma (standard deviation in millimeters in integer format)

Column 39-44 Outlier (integer format)

Column 45-50 Sensor temperature (tenth of degrees C in integer format)

Column 51-52 Sensor type (Z1 for generic or pressure)

Column 53-53 blank

Column 54-54 Data Source (S for Satellite, D for Diskette)

Sample data:

85169901AUG 17 2007 05:00 1138 23 0 308Z1 D

85169901AUG 17 2007 05:06 1126 26 0 308Z1 D

85169901AUG 17 2007 05:12 1107 26 1 309Z1 D

Note: pressure data must be accompanied by documented staff observations as listed

in Section 4.2.2 and 4.2.4, if applicable.

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4.6.4 Tabulations and Tidal Datums

For contract surveys, the contract hydrographer shall provide digital and hard copies

of tabulations of staff/gauge differences, hourly heights, high and low waters, monthly

means, and water level datums for the entire time series of observations from each water level station. Along with the final contractor computed tidal datums, the contractor

shall provide copies of the tide-by-tide and/or monthly mean simultaneous comparison

sheets from which the final tidal datums were determined. Audit trails of data edits and

gap-filling shall be summarized and provided also.

The digital tabulation files for hourly heights, high and low waters, monthly means, and

station datum shall have the following formats:

Each input record (including the final record) ends with a carriage return and excludes

any extraneous characters such as trailing blank spaces for all types of water level

data (6-minute water level data, hourly height, high/low, monthly means, and station

datum).

Hourly Height data Format:

Column 1- 7 Station ID (7 digits, assigned in the project instructions)

Column 8- 8 Blank

Column 9-16 Date (YYYYMMDD format, e.g. 20070120)

Column 17-17 Blank

Column 18-19 Hours (2 digits 00-23, use leading zeros)

Column 20-20 : (colon)

Column 21-22 Minutes (2 digits 00-54, use leading zeros)

Column 23-23 Blank

Column 24-30 Water level value in meters (F7.3 format, e.g. 123.456)

Sample data:

9414290 20040101 00:00 123.456

Hourly height data file shall be named in the following format:xxxxxxx.w2.DAT, where

xxxxxxx is the seven digit station number, w2 is the product code for the hourly heights

data, and DAT is the extension. This is the format needed when the data is loaded into

CO-OPS DMS database.

High/Low Data Format:

Column 1- 7 Station ID (7 digits, assigned in the project instructions)

Column 8- 8 Blank

Column 9-16 Date (YYYYMMDD format, e.g. 20070120)

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Column 17-17 Blank

Column 18-19 Hours (2 digits 00-23, use leading zeros)

Column 20-20 : (colon)

Column 21-22 Minutes (2 digits 00-54, use leading zeros)

Column 23-23 Blank

Column 24-30 Water level value in meters (F7.3 format, e.g. 123.456)

Column 31-31 Blank

Column 32-33 Water level high/low type (H, L, HH, or LL)

Sample data:

9414290 20040101 00:00 123.456 HH

Definition of Acronym:

H: Higher low water level value

L: Lower high water level value

HH: Higher high water level value

LL: Lower low water level value

High and low data file shall be named in the following format: xxxxxxx.w3.DAT, where

xxxxxxx is the seven digit station number, w3 is the product code for the high/low

data, and DAT is the extension. This is the format needed when the data is loaded into

CO-OPS DMS database.

Monthly Mean Data Format:

Column 1- 7 Station ID (7 digits, assigned in the project instructions)

Column 8- 8 Blank

Column 9- 12 Year (YYYY format, e.g. 2007)

Column 13- 13 Blank

Column 14- 15 Month (in 2 digits 01-12, use leading zeros)

Column 16- 16 Blank

Column 17- 23 MHHW in meters (F7.3 format, e.g. 123.456)

Column 24- 24 Blank

Column 25- 31 MHW in meters (F7.3 format, e.g. 123.456)

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Column 32- 32 Blank

Column 33- 39 DTL in meters (F7.3 format, e.g. 123.456)

Column 40- 40 Blank

Column 41- 47 MTL in meters (F7.3 format, e.g. 123.456)

Column 48- 48 Blank

Column 49- 55 MSL in meters (F7.3 format, e.g. 123.456)

Column 56- 56 Blank

Column 57- 63 MLW in meters (F7.3 format, e.g. 123.456)

Column 64- 64 Blank

Column 65- 71 MLLW in meters (F7.3 format, e.g. 123.456)

Column 72- 72 Blank

Column 73- 79 GT in meters (F7.3 format, e.g. 123.456)

Column 80- 80 Blank

Column 81- 87 MN in meters (F7.3 format, e.g. 123.456)

Column 88- 88 Blank

Column 89- 95 DHQ in meters (F7.3 format, e.g. 123.456)

Column 96- 96 Blank

Column 97-103 DLQ in meters (F7.3 format, e.g. 123.456)

Column 104-104 Blank

Column 105-111 Maximum Water Level in meters (F7.3 format, e.g. 123.456)

Column 112-112 Blank

Column 113-120 Maximum Water Level Date (in YYYYMMDD format, last occurrence)

Column 121-121 Blank

Column 122-123 Maximum Water Level Hour (2 digits 00-23, use leading zeros)

Column 124-124 : (colon)

Column 125-126 Maximum Water Level Minute (2 digits 00-54, use leading zeros)

Column 127-127 Blank

Column 128-128 Maximum Water Level occurrences (1 digit)

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Column 129-129 Blank

Column 130-136 Minimum Water Level in meters (F7.3 format, e.g. 123.456)

Column 137-137 Blank

Column 138-145 Minimum Water Level Date (in YYYYMMDD format, last occurrence)

Column 146-146 Blank

Column 147-148 Minimum Water Level Hour (2 digits 00-23, use leading zeros)

Column 149-149 : (colon)

Column 150-151 Minimum Water Level Minute (2 digits 00-54, use leading zeros)

Column 152-152 Blank

Column 153-153 Minimum Water Level occurrences (1 digit)

Sample data (with column ruler):

Definition of Acronym:

MHHW Mean Higher High Water

MHW Mean High Water

DTL Diurnal Tide Level

MTL Mean Tide Level

MSL Mean Sea Level

MLW Mean Lower Water

MLLW Mean Lower Low Water

GT Great Diurnal Tide Range

MN Mean Range of Tide

DHQ Diurnal High Water Inequality

DLQ Diurnal Low Water Inequality

MAX_WL Maximum Water Level during the Month measurement period

MAX_DATE Date of Maximum Water Level

MAX_HOUR Hour of Maximum Water Level

MAX_MIN Minute of Maximum Water Level

MAX_OCCUR Number of occurrences during the month the Water Level meets the MAX_WL

MIN_WL Minimum Water Level during the Month measurement period

MIN_DATE Date of Minimum Water Level

MIN_HOUR Hour of Minimum Water Level

MIN_MIN Minute of Minimum Water Level

MIN_OCCUR Number of occurrences during the month the Water Level meets the MIN_WL

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Monthly Means data file shall be named in the following format: xxxxxxx.w5.DAT, where

xxxxxxx is the seven digit station number, w5 is the product code for the monthly

means data, and DAT is the extension. This is the format needed when the data is

loaded into CO-OPS DMS database.

Station Datum Data Format:

Column 1- 7 Station ID (7 digits, assigned in the project instructions)

Column 8- 16 Blank

Column 17- 23 MHHW in meters (F7.3 format, e.g. 123.456)

Column 24- 24 Blank

Column 25- 31 MHW in meters (F7.3 format, e.g. 123.456)

Column 32- 32 Blank

Column 33- 39 DTL in meters (F7.3 format, e.g. 123.456)

Column 40- 40 Blank

Column 41- 47 MTL in meters (F7.3 format, e.g. 123.456)

Column 48- 48 Blank

Column 49- 55 MSL in meters (F7.3 format, e.g. 123.456)

Column 56- 56 Blank

Column 57- 63 MLW in meters (F7.3 format, e.g. 123.456)

Column 64- 64 Blank

Column 65- 71 MLLW in meters (F7.3 format, e.g. 123.456)

Column 72- 72 Blank

Column 73- 79 GT in meters (F7.3 format, e.g. 123.456)

Column 80- 80 Blank

Column 81- 87 MN in meters (F7.3 format, e.g. 123.456)

Column 88- 88 Blank

Column 89- 95 DHQ in meters (F7.3 format, e.g. 123.456)

Column 96- 96 Blank

Column 97-103 DLQ in meters (F7.3 format, e.g. 123.456)

Column 104-104 Blank

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Column 105-111 Maximum Water Level in meters (F7.3 format, e.g. 123.456)

Column 112-112 Blank

Column 113-120 Maximum Water Level Date (in YYYYMMDD format, last occurrence)

Column 121-121 Blank

Column 122-123 Maximum Water Level Hour (2 digits 00-23, use leading zeros)

Column 124-124 : (colon)

Column 125-126 Maximum Water Level Minute (2 digits 00-54, use leading zeros)

Column 127-127 Blank

Column 128-128 Maximum Water Level occurrences (1 digit)

Column 129-129 Blank

Column 130-136 Minimum Water Level in meters (F7.3 format, e.g. 123.456)

Column 137-137 Blank

Column 138-145 Minimum Water Level Date (in YYYYMMDD format, last occurrence)

Column 146-146 Blank

Column 147-148 Minimum Water Level Hour (2 digits 00-23, use leading zeros)

Column 149-149 : (colon)

Column 150-151 Minimum Water Level Minute (2 digits 00-54, use leading zeros)

Column 152-152 Blank

Column 153-153 Minimum Water Level occurrences (1 digit)

Sample data (with column ruler):

Definition of Acronyms for Station Datum data are same as that for the Monthly Mean

data.

Station datum data file shall be named in the following format: xxxxxxx.w7.DAT, where

xxxxxxx is the seven digit station number, w7 is the product code for the station datum

data, and DAT is the extension. This is the format needed when the data is loaded into

CO-OPS DMS database.

If the Greenwich High Water Interval (HWI) and Greenwich Low Water Interval (LWI)

are available, then contractor shall provide that information in F5.2 format and that file

shall be named as xxxxxxx.GWI.txt, where xxxxxxx is the seven digit station number.

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4.6.5 Tide Reducers and Final Zoning and Final Tide Note

The final zoning scheme shall be fully supported by documentation of data and methodology which comprised the final zoning model. The contractor must provide final tidal

zoning scheme digitally in the MAPINFO, ARCVIEW, or CARIS compatible format. Final

tidal zoning scheme in AUTOCAD format is not acceptable.

Final tide reducers shall be submitted in the specified format.

All documentation listed below shall be forwarded to CO-OPS:

• Contractor created summary files.

• Documentation of NOS summary files utilized for final zoning

• GIS compatible zoning development steps in MapInfo©, ArcGIS© or CARIS© format including geographical presentation of summary data and cophase/corange

maps, if appropriate

• GIS compatible digital final zoning files

• Final tide reducer data files

• Final Tide Note

The final zoning scheme shall be fully supported by documentation of data and methodology which derived the final zoning model.

4.6.6 Submission and Deliverables – Documentation and Time lines

The check list in Figures 4.14 shall be used to check and verify the documentation

that is required for submission. All documentation, water level data, processed data

including hourly height, high/low data, monthly means data, and station datums data,

GPS forms and data including OPUS results, zoning and other reports (as listed above

in Section 4.6.5) as required, shall be forwarded within 15 business days of the removal

of the stations/gauges.

Submit a transmittal letter to the appropriate Contracting Officer’s Technical Representative (COTR) listing what is forwarded to CO-OPS. Submit a duplicate transmittal letter,

all data and documentation to CO-OPS POC, as listed below.

All data and documentation submitted to CO-OPS shall be retained by the contractor

for a period of not less than three years or as stipulated in the contract, whichever is

longer.

All data and documentation shall be submitted in digital format. Please refer to Section

4.6.1, 4.6.2, 4.6.3, 4.6.4, and 4.6.5 for details about various data and documentation.

Standard station documentation package includes the following:

1. Transmittal letter

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2. Field Tide note, if applicable

3. Calibration records for sensors, if applicable

4. E-Site Report, Xpert Site Report, or tide station report

5. Chartlet

6. USGS Quad map (7.5 minutes quadrangle maps)

7. Sensor test worksheet

8. Sensor elevation drawing

9. Water level transfer form (Great Lakes stations only)

10. Bench mark sketch

11. “Station To Reach” statement

12. Bench mark descriptions

13. Photographs of bench marks, station, DCP, equipment, and vicinity in digital and

paper format

14. Levels (raw) (electronic files) and field notes of precise leveling

15. Abstract of precise leveling

16. Datum offset computation worksheet or Staff/Gauge difference work sheet as

appropriate showing how sensor “zero” measurement point is referenced to the

bench marks.

17. Calibration certificates for Invar leveling rods, if applicable

18. Staff to gauge observations, if applicable

19. Agreements, MOU, contract documents, utilities/pier agreements, etc., if applicable

20. Other information as appropriate, or as specified in the contract

21. Water level data, 6-minute data, all tabulated data, such as hourly heights, high

and low, monthly means, and station datum data in the specified format. (refer to

Section 4.6.3 and 4.6.4)

22. GPS data and documentation, as applicable

23. Contractor created summary files, final zoning, final tide reducer data, final tide

note, and cophase/corange maps if appropriate, etc.

Generally, for established water level stations, the bench mark sketch, chartlet, and

"To Reach" statement need only be submitted if those items have been revised during

the station maintenance.

When using the electronic/barcode system, the data disk and hard copies of the abstract and bench mark description or recovery notes shall be submitted. For optical

levels, submit the raw levels and the leveling abstract.

For submission in electronic format, the station documentation shall be organized by

various folders under the main station number folder, and then pertinent information

shall be placed in the various folders and submitted on a digital media such as DVD/CDROM etc.

83
Here is an example of submission of the electronic folders for San Francisco tide station:

9414290 San Francisco FY 08 Installation

/Transmittal letter

/Field Tide Note

/Calibration records for sensors, if applicable

/Site Report or tide station report

/Chartlet and USGS Quad maps

/Sensor test worksheet

/Sensor elevation drawing

/Bench mark sketch

/Bench mark descriptions and “Station To Reach” statement

/Photographs of bench marks, station, DCP, equipment, and vicinity in digital and paper

format

/Levels (raw) (electronic files) and field notes of precise leveling

/Abstract of precise leveling

/Staff to gauge observations, if applicable

/Datum offset computation worksheet or Staff/Gauge difference work sheet (elevation

of sensor zero measurement point referenced to bench marks)

/Calibration certificates for Invar leveling rods, if applicable

/Agreements, MOU, contract documents, utilities/pier agreements, etc., if applicable

/Other information as appropriate, or as specified in the contract

/Water level data (6-minute, hourly heights, high/low, monthly means, station datum)

/GPS data and documentation

/Final tidal zoning, final tide reducers, final tide note, summary files, cophase/corange

maps

Submit only required GPS deliverables (data and documentation) on a separate DVD/CDROM, so that CO-OPS can forward that information to NGS. for example, GPS submission

for San Francisco tide station will be as follows:

9414290 San Francisco

/GPS data and documentation, as applicable

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Submit one copy of all the documentation, water level data, including GPS data and

documentation, final tidal zoning, final tidal reducers, final tide note, etc., in digital

format. Submit one copy in digital format of the only required GPS deliverables (GPS

documentation and data including OPUS results) on a separate CD-ROM/DVD for transfer to NGS.

Submit the completed station package to:

Chief, Requirements and Development Division

NOAA/NOS/CO-OPS/RDD

SSMC 4, Station # 6531

1305 East-West Highway

Silver Spring, MD 20910-3281

Tel # 301-713- 2897 X 145

Submit at the same time an original transmittal letter to the COTR, listing what was

forwarded to CO-OPS.

4.7 Guidelines and References

References for the water level measurement and leveling requirements issued by the

NOS Center of Operational Oceanographic Products and Services (CO-OPS) and the

National Geodetic Survey (NGS) are listed below.

Some of these documents are available on CO-OPS web site at http://www.CO-OPS.nos.

noaa.gov.

1. Next Generation Water Level Measurement System (NGWLMS) Site Design, P reparation, and Installation Manual, NOAA/NOS, January 1991.

2. User’s Guide for the Installation of Bench Marks and Leveling Requirements for

Water Level Stations, NOAA/NOS, dated October 1987.

3. User’s Guide for Writing Bench Marks Descriptions, NOAA/NOS, Updated January

2003.

4. User’s Guide for Electronics Levels, NOAA/NOS, updated January 2003.

5. User’s Guide for 8200 Bubbler Gauges, NOAA/NOS, updated February 1998.

6. User’s Guide for 8200 Acoustic Gauges, NOAA/NOS, updated August 1998.

7. User’s Guide for 8210 Bubbler Gauges, NOAA/NOS, updated February 2001.

8. User’s Guide for GPS Observations, NOAA/NOS, updated March 2007.

9. Tidal Datums and Their Applications, Special Publication No. CO-OPS 1, NOAA/NOS,

June 2000.

10. Manual of Tide Observations, U.S. Department of Commerce, Publication 30-1,

Reprinted 1965.

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11. Tidal Datum Planes, U.S. Department of Commerce, Special Publication No.135,

Marmer 1951.

12. Tide and Current Glossary, U.S. Department of Commerce, NOAA, NOS, October

1989.

13. Standing Project Instructions: Great Lakes Water Levels, June 1978.

14. NOAA Technical Report NOS 64 “Variability of Tidal Datums and Accuracy in Determining Datums from Short Series of Observations”, Swanson, 1974.

15. Data Quality Assurance Guidelines for Marine Environmental Programs, Robert J.

Farland, Office of Ocean Engineering, NOAA, March, 1980.

16. System Development Plan, CORMS: Continuous Operational Real-Time Monitoring

System, NOAA Technical Report NOS OES 014, U.S. Department of Commerce,

NOAA, NOS February, 1997.

17. NGWLMS GOES MESSAGE FORMATTING, Phil Libraro, 1/2003.

18. Computational Techniques for Tidal Datums, NOAA Technical Report NOS CO-OPS

2, U.S. Department of Commerce, NOAA, NOS, DRAFT December 1998.

19. Standards and Specifications for Geodetic Control Networks, Federal Geodetic Control Committee, September 1984.

20. NOAA Technical Memorandum “NOS NGS-58, Guidelines for Establishing GPS-Derived

Ellipsoid Heights (Standards 2 cm and 5 cm), Version 4.3", November 1997.

21. Geodetic Leveling, NOAA Manual NOS NGS 3, U.S. Department of Commerce,

NOAA, National Ocean Survey, August, 1981.

22. NOAA Special Publication NOS CO-OPS 1Tidal Datums and Their Applications, February 2001.

23. “Attachment R, Requirements for Digital Photographs of Survey Control, NGS, July

2005”

24. Xpert Operations and Maintenance Manual, October 2006.

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5 Depth Sounding

Depths shall be recorded in meters, with a precision of at least centimeters. This precision shall be maintained throughout the processing pipeline and be maintained in the

digital data.

Depths reported in the Descriptive Report (DR), other reports or correspondence should

be rounded to the nearest centimeter and have the associated Total Propagated Uncertainty (TPU) (or Total Propagated Error (TPE) as it is often referred to) of the depth listed

to the nearest centimeter.

5.1 Multibeam and Other Echosounders

Many SOWs or Hydrographic Project Instructions require the use of multibeam echosounders

for NOS Hydrographic Surveys however there are occasions where there may be a requirement for single beam or in the future Phase Differencing Bathymetric Systems.

Therefore, NOS Specifications, listed in section 5.1 and all its subsections, will refer to

multibeam echosounders unless otherwise specified.

5.1.1 Accuracy and Resolution Standards

As mentioned in Section 1, the NOS Specifications are partly based on the IHO Standards for Hydrographic Surveys as outlined in Special Publication 44 (S-44). IHO S-44

specifications are suggested minimum standards that member states may choose to

follow. The IHO minimum standards for accuracy are used in the NOS Specifications as

a convenient point of reference. When the NOS Specifications refer to an IHO Order, it is

usually in terms of the final accuracy of a measurement. No other claim for “meeting”

an IHO Order survey is implied.

In the future, NOS Specifications will only define the requirements for grid accuracy

and grid resolution, subjects not covered in the current version of S-44 (5th Edition,

February 2008). As an interim step, sounding accuracy is still defined in the NOS Specifications, in addition to grid requirements.

5.1.1.1 Accuracy Standards NOS standards for the accuracy of measured depths

in hydrographic surveys apply to the systematic measurement of general water depths

and to the least depths determined over wrecks and obstructions. By extension, they

also apply to the elevations of rocks or other features which uncover at low water

and to the measurement of overhead clearances. These standards apply regardless

of the method of determination; whether by single beam echosounder, multibeam

echosounder, lead line or diver investigation.

The total sounding error in a measured depth at the 95 percent confidence level, after

systematic and system specific errors have been removed, shall not exceed:

±

q

a

2 + (b ? d)

2

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where in depths less than 100 meters, a = 0.5 meters and represents the sum of all

constant errors, (b * d) represents the sum of all depth dependent errors, b = 0.013

and is a factor of depth dependent error, and d is depth (in meters) (IHO S-44, Order 1).

In depths greater than 100 meters, a =1.0, b=0.023, d=depth (IHO S-44, Order 2).

The maximum allowable error in measured depth includes all inaccuracies due to residual systematic and system specific instrument errors; the speed of sound in water;

static vessel draft; dynamic vessel draft; heave, roll, and pitch; and any other sources

of error in the actual measurement process, including the errors associated with water

level (tide) variations (both tidal measurement and zoning errors).

5.1.1.2 Multibeam Resolution Standards The ability to detect objects is a function of the beam width, beam foot print on the seafloor, bottom detection algorithms,

and the spacing of soundings on the seafloor, both across track and along track. The

feature detection capabilities of the multibeam equipment shall be consistent with the

coverage requirements in section 5.1.2. Along track coverage is also dependent on the

sounding ping rate and the speed of the survey vessel.

5.1.1.3 Gridded Data Specifications In the Navigation Surface approach, survey

data are archived as a certified digital terrain model rather than as a set of verified

soundings. HSD has determined that the highest resolution the data can support is

rarely needed for navigation products. A compromise grid resolution between the highest resolution possible and a resolution required for navigation products has the advantage of preserving high-resolution data for other users without needlessly burdening NOAA field units and contractors. The end product of creating a nautical chart is

then created from scale-appropriate generalizations of the Navigation Surface elevation model.The Navigation Surface requires that each sounding have a horizontal and

vertical uncertainty. To do this effectively, an error model is needed for all systems

supplying measurements to compute the sounding; including not only the multibeam

echosounder, but the GPS sensors, the heave, pitch, and roll sensors, the sound speed

measuring devices, tide gauges, draft measurements, dynamic draft, and anything else

that contributes to the calculation of a sounding. Once this comprehensive error model

is assembled, then all the inherent errors in each measurement can be propagated from

the measurement platform to each individual sounding. Only when each sounding has

an associated Total Propagated Uncertainty (TPU), can we combine the soundings into

a Navigation Surface with each node having a depth and uncertainty attribute.

Currently, the open source Bathymetric Attributed Grid (BAG) standard format does

not include support for multi-resolution grids. The BAG format was developed to create an open source exchange format for gridded data. The Open Navigation Surface Working Group (ONSWG) was formed to develop the format. ONSWG is comprised of government and private sector groups. The primary goals of the ONSWG

are to define an open, platform independent, grid database file format suitable for access, archival, and interchange of Navigation Surface results, and to develop an open

source software access library to operate on this format. For more information see

http://www.opennavsurf.org. The CARIS Bathymetry with Associated Statistical Error

(BASE) surface has multi-resolution functionality; however, it is not presently approved

for NOAA surveys. Therefore, the survey area will typically be required to be subdivided

into several grids of varying resolution dependent on depth.

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The hydrographer will adjust the extents and number of grids based on the bathymetry

of the survey area, the type of multibeam sonar used and other factors. However,

adjacent grids shall always overlap in depth to ensure no gaps in coverage exist at the

transition from one depth grid to another.

The hydrographer shall also consider the size of objects that they are attempting to

detect. A grid must have twice the resolution of the object (i.e. a 1 meter grid would be

required to properly depict a 2 meter cube).

The hydrographer has the responsibility to review the surface and ensure that it truly

reflects the conditions in the survey area. No algorithm will ever perfectly model the

seafloor. Especially in the case of small diameter objects (pilings, small rocks, etc.), depending on the resolution of the gridded surface, it is unlikely that the surface will capture the absolute least depth on all features. An experienced hydrographer, therefore,

must review the data and occasionally select “designated” soundings which override

the gridded surface and force the model to recognize the shoal sounding.

Designated Soundings In depths less than 20 meters, a designated sounding should

be selected when the difference between the gridded surface and reliable shoaler

sounding(s) are more than one-half the allowable IHO error budget for the depth, for

navigationally significant features/areas. For instance, a rock on a steep slope should

be selected if the hydrographer determines it is a navigationally significant feature

based on the vessel traffic in the area. The hydrographer should also consider the

scale of survey when selecting designated soundings. When the distance between two

depths is less than 2mm at the scale of survey (20m for 1:10,000 scale) then only the

shoalest depth needs to be designated.

In depths greater than 20 meters, a designated sounding should be selected when the

difference between the gridded surface and reliable shoaler sounding(s) are more than

the allowable IHO error budget for the depth, while taking into consideration the scales

of the survey as discussed above.

Conversely, if noisy data, or ‘fliers’ are incorporated into the gridded solution, the surface may be shoaler than the true seafloor. In such cases the spurious soundings will

need to be rejected and the surface recomputed. Therefore, if noisy data causes the

surface to be shoaler than expected by an amount greater than the IHO error budget

for depth, then the noisy data shall be rejected and the surface recomputed.

If an excessive number of designated soundings need to be selected, the hydrographer may need to reassess the grid resolution of the surface. If the data supports a

higher resolution grid, the resultant surface may model the seafloor more accurately

and result in fewer designated soundings being required. In some cases, often in rocky

nearshore areas, the least depths of many features in a relatively small area may fail to

be preserved, even by very high resolution BASE surfaces. In these instances the hydrographer shall designate the least depths on the most significant shoalest features

as required by the navigational use of the area and the scale of the survey.

Uncertainty By definition each node of the grid includes not only a depth value,

but other attributes including “uncertainty”. The uncertainty value for the grid shall

be the greater of the standard deviation and the a priori uncertainty at each node.

The hydrographer shall include a discussion in the DAPR on how the uncertainty was

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computed on each individual sounding and how the uncertainty was computed on the

grid, with a justification for that methodology.

The hydrographer shall examine the finalized grids and explain in the DR any areas of

unusually high uncertainty.

5.1.2 Coverage

In general, there are three classifications of multibeam coverage: Object Detection

Coverage, Complete Coverage and Set Line Spacing. The survey coverage technique

will be specified in the Statement of Work or Project Instructions. Field operations shall

be conducted such that the accuracy requirements in Section 5.1.1 are met for the

entire multibeam coverage area and the multibeam is operated as stated in section

5.1.1.2.

In some cases a hybrid coverage technique may be used, such as, 100% side scan with

Complete Multibeam Coverage. The requirements for any assigned hybrid coverage

will be described in the Statement of Work or Project Instructions. If single beam and

multibeam are specified in the Hydrographic Survey Project Instructions or Statement

of Work and they both fall in a common area, then a separate single beam surface is

required.

These requirements shall be followed by contractors unless stated otherwise in the

SOW or an exemption is approved by the COTR. NOAA field units shall refer to the

Project Instructions for specifics. Any deviations from the requirements shall be discussed in the Descriptive Report and NOAA field units shall notify HSD Operations and

either AHB or PHB, as appropriate.

The experienced hydrographer should use discretion when using the following gridding

requirements described in sections 5.1.2.1, 5.1.2.2, and 5.1.2.3. If the required resolution of the grid for an area does not seem appropriate, the hydrographer should notify

HSD or the appropriate COTR to discuss exceptions to the gridding specifications and

recommend alternate gridding resolutions. The discussion should occur early in the

data acquisition phase of the project, in case the exception is not agreed upon. For

instance, a very narrow high resolution grid along shore in a ”steep and deep” fjord

serves no purpose. Also, object detection coverage gridding specifications may not be

necessary areas where object detection requirements are met by side scan sonar or

other technologies (and where objects found have an accurate least depth determined

with an appropriate echosounder).

The scale of the survey shall be taken into consideration when determining the significance of features. When 2 features lie within 2mm at the scale of survey from each

other, only the shoalest is required to be included in the grid.

5.1.2.1 Object Detection Coverage

• Detect and include in the grid bathymetry all significant features measuring at

least 1m x 1m x 1m in waters up to 20 meters deep, and a cube measuring 5% of

the depth in waters 20m and deeper.

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• Grid resolution shall be 0.5m in waters less than 20m deep, and not greater than

5% of the water depth in waters 20m and deeper. At least 95% of all nodes on the

surface shall be populated, with at least 5 soundings.

• The maximum propagation distance shall be no more than the grid resolution divided by √2.

• For depths up to 30m no holiday spanning more than 3 nodes; for depths deeper

than 30m, hydrographer’s discretion shall be used, notwithstanding any violation

of other coverage requirements.

• No holidays over tops of potentially significant features.

• The following grid-resolution thresholds as a function of depth range; shall be used

unless an exception is approved as described in Section 5.1.2. Object detect coverage is rarely needed in depths greater than 30m.

Depth Range (m) Resolution (m)

0–23 0.5

20-40 1

5.1.2.2 Complete Multibeam Coverage

• Detect and include in the grid bathymetry all significant features measuring 2m x

2m horizontally, and 1m vertically in waters less than 20m deep

• Detect features measuring 10% of depth horizontally and approximately 5% vertically in waters deeper than 20m.

• Grid resolution shall be 1m in waters less than 20m deep, and approximately 5% of

the water depth in waters 20m and deeper. Coarser resolutions may be warranted

in certain areas due to bottom topography (“steep and deep”), or if side scan

data is also collected, or other project specific reasons. However, there is rarely a

circumstance where the depths encountered are deep enough to warrant the use

of grid resolutions greater than 10m. The coarsest resolution shall be 8m for areas

with depths up to 350m and a 16m resolution for areas with depths greater than

350m.At least 95% of all nodes on the surface shall be populated, with at least 5

soundings.

• The maximum propagation distance shall be no more than the grid resolution divided by √2.

• No holiday spanning more than 3 nodes in waters less than 30m; for depths deeper

than 30m, hydrographer’s discretion shall be used, notwithstanding any violation

of other coverage requirements.

• No holidays over tops of potentially significant features.

• All significant shoals or features found in waters less than 30m deep shall be developed to Object Detection standards or designate soundings from nadir beam

developments.

• The following grid-resolution thresholds as a function of depth range shall be used

unless an exception is approved as described in Section 5.1.2.

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Depth Range (m) Resolution (m)

0-23 1

20-52 2

46-115 4

103-350 8

350+ 16

5.1.2.3 Set Line Spacing The hydrographer shall conduct multibeam and single

beam operations at the line spacing specified in the Hydrographic Survey Project Instructions or Statement of Work. For example, set line spacing may be employed in the

following scenarios: (1) when acquiring multibeam data concurrently with side scan

sonar operations (sometimes referred to as “skunk-stripe” coverage, where the side

scan swath is wider than the multibeam swath) and (2) when acquiring single beam

data in areas that are too shallow for efficient multibeam operations, or otherwise too

risky of an area to use multibeam equipment.

• For multibeam operations the requirements are the same within the swath, as for

Complete Coverage above. Note: that in a “skunk striping” scenario (see above)

elements of object detection are also in operation, due to side scan sonar data

coverage and any associated contact scanning requirements.

• For single beam operations the resolution of the single beam grid should be no

higher than between 3 to 5 meters and be multiples of any overlapping multibeam

grids set such that the geometry is in alignment.

• Splits between set line spacing shall be acquired for both multibeam and single

beam hydrography to adequately define shoals and to verify currently-charted

soundings that are shoaler than any adjacent limits of echosounder coverage. If

charted sounding falls between 2 sounding lines, and the charted depth is shoaler

than adjacent depths from both lines, then the field unit must ”split” the lines to

verify or disprove the charted sounding.

5.1.3 Corrections to Echo Soundings

To meet the accuracy and resolution standards for measured depths specified in Section

5.1.1, and to create a BAG that includes an accurate uncertainty layer, the hydrographer must conduct an error analysis of their survey systems.

Precise measurements are fundamental to the field of hydrography. Synchronization

of multiple sensors with the sonar system is essential for meaningful spatial analysis

of the data. All measurements, however careful and scientific, are subject to some

uncertainties. Error analysis is the study and evaluation of these uncertainties with the

purpose of estimating the extent of the uncertainties and when necessary, reducing

them.

Uncertainty-based processing has fundamentally altered bathymetric data processing

and product creation. The validity and usefulness of the results are directly correlated

to the accuracy of the individual estimates that compose the error model. The error

model for CARIS contains uncertainties associated with the sensor and sonar, physical offsets, latency, draft, loading, sound speed and tide and tidal zoning (NOAA field

92
units may refer to section 4.2.3.6 of the OCS Field Procedures Manual for more information). Non-CARIS users must build a similar model of all the correctors to the depth

measurement and the associated uncertainties.

In recognition of the possibility that some discrepancies in soundings may not be detected until the final processing phase of the survey, the determination and application

of corrections to echo soundings must be accomplished and documented in a systematic manner. In addition, it is preferable that all corrections be applied in such a way

that the on-line values may be removed and replaced with a revised set of correctors

during office processing. Corrections to echo soundings are divided into five categories,

and listed below in the sequence in which they are applied:

Instrument error corrections account for sources of error related to the sounding

equipment itself.

Draft corrections shall be added to the observed soundings to account for the depth

of the echosounder transducer below the water surface.

Dynamic draft corrections shall be applied to soundings to correct the vertical displacement of the transducer, relative to its position at rest, when a vessel is underway.

Speed of sound corrections shall be applied to soundings to compensate for the fact

that echosounders may only display depths based on an assumed sound speed profile

while the true speed may vary in time and space.

Attitude corrections shall be applied to multibeam soundings to correct the effect

of vessel motion caused by waves and swells (heave, roll, pitch) and the error in the

vessel’s heading

5.1.3.1 Instrument Error Corrections In modern digital sounding instruments,

instrument errors are generally small and of a fixed magnitude independent of the

observed depth. Proper set up and adjustment of digital sounding equipment using

internal checks and echo simulators will often eliminate instrument error entirely. However, to ensure the proper operation of echosounders, “confidence checks” shall be

conducted periodically.

For single beam echosounders, a comparison should be made at least once per week

with depths from bar checks, lead lines, or other single beam echosounders.

For multibeam echosounders, comparisons should be made at least once per week

between the nadir (vertical) beam of the multibeam and a single beam system or lead

line. On surveys where multiple vessels collect data that overlaps with each other to

allow comparison of depths, the frequency of formal confidence checks can be reduced

to once per survey. In addition, frequent checks should be made between the overlap

of mainscheme and crosslines collected on different days. These comparisons should

be made frequently during data collection to find errors promptly, and not saved until

final data processing after the field party has left the working grounds.

Comparisons should be conducted during calm sea conditions, preferably in areas with

a relatively flat sandy bottom. Any differences should be investigated, and if, after

analysis, a corrector is necessary, it should be applied with an explanation of the cause

of the difference explained in the Descriptive Report (DR) section B.2, Quality Control.

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5.1.3.2 Draft Corrections The corrections for draft account for the depth of the

transducer reference point below the surface of the water. Draft corrections comprise

a value for the draft of the vessel at rest, sometimes known as static draft, and settlement corrections which compensate for the variation in draft that occurs when the

vessel is making way. The sum of the static draft and the settlement and squat correctors is known as the dynamic draft. Draft is transducer-specific. When more than

one transducer is fixed to a vessel, the hydrographer must exercise care to apply the

proper draft correction for each transducer. In addition to the draft values, to complete

the vessels’ error model, the hydrographer must determine the uncertainty associated

with all draft values.

Static Draft The static draft, as an echo-sounding correction, refers to the depth

of the transducer reference point below surface of the water when the vessel is not

making way through the water. The required frequency of static draft measurements

depends upon the range of variation in the vessel draft and the depths of water to be

surveyed. For depths of 30 m or less, the static draft shall be observed and recorded

to at least the nearest 0.1 m. Measurements are required with sufficient frequency to

meet this criterion. When sounding in waters deeper than 30 m, the static draft shall

be observed and recorded to at least the nearest 0.2 m.

Draft values for small vessels such as survey launches should be determined for the

range of loading conditions anticipated during survey operations (maximum and minimum). Draft values for larger vessels must be observed and entered into the record

before departing from and upon returning to port. In both cases, the draft should be

determined by averaging the max/min or beginning/ending values if the differences do

not exceed ±0.2 m. Otherwise, the applicable draft should be determined in at least

0.1 m increments. If significant changes to a vessel’s draft (greater than ±0.1 m) occur,

draft values shall be modified and applied accordingly.

Loading and static draft uncertainties typically represent a small percentage of the total

error budget. However, the accuracy of the error model and the results of BAG surface

processing are dependent on knowledge of all the uncertainty values that compose the

model.

Dynamic Draft Transducers are generally displaced vertically, relative to their positions at rest, when a vessel is making way. Depth measurements are correspondingly

affected by these vertical displacements. The displacements may be of sufficient magnitude to warrant compensation, especially when sounding at moderate to high speeds

in shoal water. The factors accountable for this vertical displacement are called settlement. Major factors that influence dynamic draft are hull shape, speed, and depth of

water beneath the vessel.

Settlement is the general difference between the elevations of a vessel when at rest

and when making way. For lower speed, non-planing vessels, settlement is caused

by a local depression of the water surface. Settlement is not an increase in the vessel

displacement and, therefore, cannot be determined by reference to the water surface in

the immediate vicinity. Vessels surveying at higher speeds may experience a negative

settlement, or lift, when planing.

Squat refers to changes in trim of the vessel when making way and is generally manifested by a lowering of the stern and rise of the bow. Occasionally, the bow lowers

94
on smaller vessels. Squat does not appreciably affect transducer depth on transducers

mounted near amidships. Settlement, on the other hand, is almost always significant

at normal sounding speeds, regardless of transducer location.

If a Heave-Roll-Pitch (HRP) sensor is used to determine changes in squat, care must be

taken to ensure that squat is not corrected for twice. Conversely, if attitude corrections

are not used in single beam data processing, the dynamic draft correction must include

any appreciable effects due to vessel trim.

Combined effects of dynamic draft at the full range of sounding speeds must be determined to at least 0.05 meter precision, by the hydrographer at least once a year

for each vessel, including launches and skiffs used for hydrographic surveying in shoal

or moderate depths. Follow up measurements should be made if there are any major

changes to the loading or change to the vessel power plant. When the measurements

are made, each vessel should carry an average load and have an average trim. Sounding vessel speeds (or RPM) must be entered in the hydrographic records during survey

operations to permit accurate corrections for dynamic draft.

The uncertainty value for Dynamic Draft will be dependent on the method that Dynamic

Draft was calculated. Typically, several runs at various speeds will be used to calculate

the Dynamic Draft. The uncertainty value could then be the standard deviation calculated for each speed measurement.

5.1.3.3 Speed of Sound Corrections Special note: Sound Speed or Speed of

Sound is sometimes incorrectly referred to as sound velocity in other publications and

equipment literature.

General To ensure that the overall depth measurement accuracy criteria specified

in Section 5.1.1 are met, speed of sound observations should be taken with sufficient

frequency, density, and accuracy. The accuracy with which the speed of sound correction can be determined is a complex function of the accuracy with which salinity,

temperature, and depth, or alternately, sound speed and depth, can be measured.

The speed of sound through water shall be determined using instrumentation capable

of producing sound speed profiles with errors no greater than 2 meters per second.

The sound speed profile must reach the deepest depths of the survey but the physical

measurement of sound speed need only extend to:

• 95 percent of the anticipated water depth in 30 m or less of water. For example, if

the maximum depth to be surveyed is 25 m, then the speed profile should continue

to a depth of at least 23.8 m.

• 90 percent of the anticipated water depth in depths from 30 m to 100 m.

• 85 percent of the anticipated water depth in greater than 100 m of water.

Sound speed correctors must be determined accurately and often enough to ensure

that the depth accuracy requirements in Section 5.1.1 are met. If changes in the temperature or salinity in the water column dictate that updated correctors are needed, additional sound speed profiles shall be acquired. Additionally, the hydrographer should

95
establish a means of monitoring changes in the water column between subsequent

speed casts.

Regardless of the sound speed determination system employed, an independent sound

speed measurement system must be used to establish a confidence check. Confidence

checks shall be conducted at least once per week. Include confidence check results in

Separate II, Sound Speed Profile Data (see Section 8.1.3.).

A geographic distribution of profiles may be necessary to correct for spatial and diurnal

variability. Speed corrections shall be based on the data obtained from the profile, and

not based on an averaged sound speed reading for the water column. Survey specific

sound speed information shall be included in Separate II, Sound Speed Profile Data (see

Section 8.1.3 Descriptive Report Supplemental Records).

The hydrographer shall calibrate sound speed profiler(s) no earlier than six months prior

to the commencement of survey operations. Calibration correctors shall be applied

to all profiler data. These instrument(s) shall be re-calibrated at intervals no greater

than twelve months until survey completion. In addition, the instrument(s) must be recalibrated when the survey is complete if the completion date is later than six months

from the date of last re-calibration. Copies of calibration data shall be included in Separate II, Sound Speed Profile Data (see Section 8.1.4 Descriptive Report Supplemental

Records), separates to be included with the survey data.

Sound Speed Corrections for Single Beam Surveys For each individual area

identified, a minimum of at least one cast each week, taken in the waters surveyed

that week, is required. The variation of physical conditions throughout a survey area or

any portion thereof may dictate that this minimum may not be sufficient. Where casts

taken early in a project indicate that physical characteristics are extremely variable,

observations of speed may be required more frequently.

Sound Speed Corrections for Multibeam Surveys The sound speed profile must

be known accurately in multibeam swath sounding for two reasons. First, as in all echosounding, the depth is computed from the product of the speed and the elapsed time

between transmission of a sound pulse and reception of its echo. Second, since sound

pulses travel at oblique angles through the water column, variations in the speed profile

will affect the path of sound through water. The sound path from the transducer to the

bottom and back will affect not only the observed depth of water, but the apparent

position of the observed sounding.

Even though sampling equipment and computer systems are capable of dividing the

water column into intervals so small as to allow close approximation of the integral expression for harmonic mean speed, practical limitations may require the hydrographer

to use a small number of discrete points on the speed profile for the purpose of correcting echo soundings. If the hydrographer chooses the inflection points of the smooth

speed profile as the discrete points for layer boundaries, the speed curve between the

points can reasonably be approximated by a straight line.

Integration of all the segments using the trapezoidal rule to approximate the area under

each layer will yield very accurate results.

For multibeam operations, the following specifications apply to sound speed profile

frequency and application:

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• One sound speed profile shall be acquired immediately before the beginning of

the data acquisition period. During the course of survey operations, changes in

the water column should be monitored at a sufficient frequency such that the

general requirements specified earlier in this section are met.

• Sound speed profiles shall be acquired in the immediate area where subsequent

data acquisition will occur.

• When using an undulating velocimeter, the real time sound speed profiles shall

extend to at least 80% of the anticipated water depth. At a minimum, one cast per

24-hour period shall extend to 95% of the anticipated water depth (30 m or less

water depth).

The uncertainty value of the sound speed measurements must be part of the vessel’s

error model. One method used by NOAA, is to use the manufacturers uncertainty values

for the measured components of conductivity, temperature and pressure. These values

must then be used to compute a total uncertainty for the profile by computing how each

components uncertainty is propagated through the sound speed computations.

A probe that measures speed of sound directly, could use the manufacturers advertised

uncertainty value.

Ideally, sound speed uncertainty should be computed based on both the unit’s accuracy and the spatial and temporal error associated with sound speed variation over the

entire survey area. However, such advanced error analysis is not currently available in

NOAA’s processing pipeline. Therefore, NOAA field units and contractors may use the

uncertainty associated with measuring the speed of sound at a specific location.

5.1.3.4 Attitude Corrections Heave, roll, pitch, heading, and navigation timing

error corrections shall be recorded in the data files and applied to all multibeam soundings. Heave and heading shall be applied for all single beam data. NOAA field units

should refer to section 4.2.3.6 of the OCS Field Procedures Manual for more guidance

on corrections to single beam data.

Heave, roll, and pitch. Heave shall be observed in no coarser than 0.05 m increments.

Roll and pitch shall be observed in no coarser than 0.1 degree increments.

Heading shall be observed in no coarser than 0.5 degree increments.

The uncertainty value for heave, roll and pitch will typically be the manufacturer’s values, assuming that the equipment is properly installed and maintained. The hydrographer must explain any variance from the manufacturer’s values.

Hydrographers using Kinematics GPS shall compensate for squat if attitude is not corrected for single beam.

5.1.3.5 Error Budget Analysis for Depths The hydrographer shall discuss (in

Section B.2 of the Descriptive Report) the methods used to minimize the errors associated with the determination of depth (corrections to echo soundings). Error estimate

ranges for six of these errors (measurement error, transducer draft error, s dynamic

draft error, sound speed error, heave error and tide/water level error) are presented

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below. These errors are inherent to hydrographic surveying and all have practical minimums that are usually achievable only under ideal circumstances or with highly specialized equipment. In addition, some errors may be dependent on depth (e.g. sound

speed).

The error ranges provided below are first order estimates to allow hydrographers to get

a basic ‘feel’ for the possible range in errors that may occur in practice. Hydrographers

should note that the root sum square of the individual errors is used in the computation

of TPU. The required depth accuracy requirements cannot be achieved if the worst error

for each sensor shown below is used.

Maximum allowable errors are specified to ensure that all errors sources are properly

managed. It should be noted that if the maximum value for each error source is used

in an error budget (i.e. root-sum-squared), the result will exceed the prescribed accuracy standard. The minimum and maximum values discussed below are at the 95%

confidence level (i.e. 2 sigma).

Measurement error: This includes the instrument error for the sounding system, the

effects of imperfectly measured roll/pitch and errors in detection of the sea floor due to

varying density of the bottom material. Multibeam systems are particularly susceptible

to this error due to the off-nadir nature of outer beams. The minimum achievable value

is expected to be 0.20 meter at 10 meters depth. The maximum allowable error is 0.30

meter plus 0.5% of the depth.

Transducer draft error: This error is controlled by variability in vessel loading, and

the techniques used to measure/monitor transducer draft. This error is depth independent with an expected minimum of 0.05 meter and an allowable maximum 0.15 meter.

Dynamic Draft error: Conventional methods of determining dynamic draft are limited by sea surface roughness and proximity of a suitable location to the survey area.

Careful application of modern methods (Real Time Kinematic GPS) will minimize this error. This error is also depth independent although the effect of dynamic draft is greater

in shallow water. The practical expected minimum is 0.05 meter and the allowable

maximum is 0.20 meter.

Sound speed error: The factors associated with this error include (1) the ability to

accurately measure sound speed or calculate sound speed from temperature, conductivity and pressure, (2) the spatial and temporal changes of sound speed throughout

the survey area and (3) how the sound speed profile is used to convert measured time

to depth. In addition, this error encompasses depth errors associated with refraction for

multibeam systems. The expected minimum is 0.20 meter and the allowable maximum

is 0.30 meter plus 0.5% of the depth.

Heave error: This error is directly dependent on the sea state and the sensitivity of

the heave sensor but is not dependent on depth. The expected minimum is 0.05 meter

and the allowable maximum is 0.20 meter.

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Tide/water level error: This error has been discussed in detail in Section 4 The

practical minimum is 0.20 meter and the allowable maximum is 0.45 meter.

5.1.3.6 Uncertainty Budget Analysis for Depths The hydrographer shall discuss (in Section B.2 of the Descriptive Report) the methods used to minimize the uncertainty associated with the determination of depth (corrections to echo soundings).

A sample of uncertainty components and common values are presented below. These

uncertainties are inherent to hydrographic surveying and all have practical minimums

that are usually achievable only under ideal circumstances or with highly specialized

equipment. The survey system uncertainty components and key survey system component offsets shall then be used to calculate the depth uncertainty estimate for the

soundings per the Total Propagated Uncertainty Model.

The hydrographer shall also discuss (in Section B.2 of the Descriptive Report) the methods used to quantify the survey systems uncertainty model. Uncertainty estimates for

all components of the sounding measurement shall be provided.

The uncertainty component values provided below are estimates to allow hydrographers to get a basic “feel” for the possible uncertainty values that may occur in practice. The values discussed below are at the 68% confidence level (i.e. 1 sigma).

Motion Sensor Uncertainties: These values include heave, pitch and roll measurement

uncertainties and can include gyro measurement uncertainty. A common value for

gyro, pitch and roll measurement uncertainty is 0.02°. A common value for heave

uncertainty is 5% of the heave amplitude or 0.05m, whichever is greater.

Navigation Sensor Uncertainty: This value includes the uncertainty in the determination

of the vessels position. This value will depend on the method of positioning used (C/A.

DGPS, PPK/RTK) and is commonly reported at 1m.

Timing Uncertainty: These values include the uncertainty in the measurement of time

stamps used in the survey system and include Navigation Sensor timing, Gyro Sensor

timing, Heave Sensor timing, Pitch Sensor timing and Roll Sensor timing. A commonly

reported value for this is between 0.005 and 0.01 seconds.

Vessel Offsets: These values include the uncertainty in the measurements made to

determine the survey system offsets. Ranges will depend on how accurately the offsets

were measured but are commonly reported between 0.001m and 0.1m.

Vessel Speed: This value includes the uncertainty in the measurement of vessel speed.

It is commonly reported as 0.03m/s plus the average current in the area.

Loading: This value includes the uncertainty in draft changes throughout the survey

due to factors such as fuel consumption, etc. Commonly reported values range between 1 and 30cm depending on the vessel, fueling frequency and frequency of draft

measurements.

Draft: This value includes the uncertainty in measurement of draft. Commonly reported

values range between 1 and 20cm depending on how accurately the draft of the vessel

can be measured.

Delta Draft: This value includes the uncertainty of the vessels dynamic draft measurements. Commonly reported values are between 1 and 3cm depending on dynamic draft

measurement methodology and magnitude.

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MRU Alignment: This value includes the uncertainties in the patch test determined bias

measurements of yaw, roll and pitch. Commonly reported values are less than 1°.

Tides: This value includes the uncertainties in the measurement of tides and the uncertainty of the tide zone model. Tidal uncertainties have been discussed in detail in

Section 4.1.6

Sound speed: This value includes the uncertainties in the measurement of sound speed

for full depth profiles and surface measurements. The factors associated with this uncertainty estimate include (1) the ability to accurately measure sound speed or calculate sound speed from temperature, conductivity and pressure, (2) the spatial and

temporal changes of sound speed throughout the survey area and (3) how the sound

speed profile is used to convert measured time to depth. Commonly reported values

range between 0.3 and 4m/s.

5.1.4 Quality Control

5.1.4.1 Multibeam Sonar Calibration Prior to commencing survey operations,

the hydrographer shall conduct a system accuracy test to quantify the accuracy, precision, and alignment of the multibeam system. Testing shall include determination of

residual biases in roll, pitch, heading, and navigation timing error and the uncertainty

of these values. These values will be used to correct the initial alignment, calibrate the

multibeam system and used in the computation of the Total Propagated Uncertainty

(TPU) for each sounding. System accuracy testing should be conducted in an area similar in bottom profile and composition to the survey area, and during relatively calm

seas to limit excessive motions and ensure suitable bottom detection. In addition, system accuracy tests should be conducted in depths equivalent to the deepest depths in

the survey area. Static transducer draft, dynamic draft corrections, sound speed corrections, and tide corrections shall be determined and applied to the data prior to bias

determination.

The order in which these biases are determined may affect the accurate calibration of

the multibeam system. The hydrographer should determine the biases in the following

order: navigation timing error, pitch, roll, heading. Variations from this order, simultaneous determination of all values, other methods of determining the biases must be

explained and justified.

Pitch and navigation timing error biases should be determined from two or more pairs

of reciprocal lines 500–1,000 m long, over a 10–20 degree smooth slope, perpendicular

to the depth curves. The lines should be run at different speeds, varied by up to 5

knots, for the purpose of delineating the along track profiles when assessing time delay.

Navigation timing error bias could also be determined from running lines over a distinct

feature (i.e., shoal) on the bottom, as long as the feature is pinged by the vertical

(nadir) beam.

Roll bias should be determined from one or more pair of reciprocal lines 500–1000 m in

length over a flat bottom. Lines should be run at a speed which will ensure significant

forward overlap.

Heading bias should be determined from two or more adjacent pairs of reciprocal survey lines, made on each side of a submerged object or feature (i.e., shoal), in relatively

shallow water. Features with sharp edges should be avoided. Adjacent swaths should

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overlap by 10–20 percent while covering the shoal. Lines should be run at a speed

which will ensure significant forward overlap.

Once calibration data have been processed and final system biases determined, the

new corrections shall be used in a performance check to ensure that the new system

biases are adequate. The hydrographer shall discuss procedures and results in Section

A. Equipment and optional Section B. Quality Control of the project Data Acquisition and

Processing Report. Copies of all system alignment, accuracy, calibration reports, and

performance checks shall be included in the Data Acquisition and Processing Report.

System accuracy testing shall be repeated whenever changes (e.g., sensor failure,

replacement, re-installations, re-configurations, or upgrade; software changes which

could potentially affect data quality) are made to the system’s baseline configuration,

or whenever assessment of the data indicates that system accuracies do not meet the

requirements in Section 5.1.1.

5.1.4.2 Positioning System Confidence Checks Confidence checks of the primary positioning system shall be conducted and recorded in the survey records at least

once every week. A successful confidence check shall compare positions from the primary system to simultaneously observed check positions from a separate, independent

system with a positional accuracy better than 10 meters. The inverse distance shall not

exceed 10 meters. If correctors for the primary positioning system are obtained from

a non-USCG differential system, then the check system must use correctors from a reference station different from the primary systems. If correctors are obtained from a

USCG differential station, the check system may use the same correctors as the primary system. The confidence checks shall be an integral part of the daily survey data

record. A summary report of positioning system confidence checks shall be included in

Separate I of “Separates to be Included with the Survey Data” (see 8.1.3).

5.1.4.3 Crosslines

General The regular system of sounding lines shall be supplemented by a series of

crosslines for verifying and evaluating the accuracy and reliability of surveyed depths

and plotted locations. Crosslines shall be run across all planned sounding lines at angles

of 45 to 90 degrees. The preferred area in which to run crosslines is in an area of gently

sloping bottom.

All crosslines shall be included in the grids that are submitted as the final bathymetric

product of the survey.

Single beam The lineal nautical miles of crosslines for single-beam surveys shall be

at least 8 percent of the lineal nautical miles of all sounding lines.

The hydrographer shall make a general evaluation of the single beam crossline to mainscheme agreement, and discuss the results in Section B of the Descriptive Report. If

the magnitude of the discrepancy varies widely over the survey, the hydrographer shall

make a quantitative evaluation of the disagreements area by area.

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Multibeam The lineal nautical miles of crosslines for multibeam surveys shall be at

least 4 percent of the lineal nautical miles of all sounding lines. An independent analysis

of the crossline and main scheme data shall be conducted. Although any crossline/main

scheme disagreements should be obvious in the attributes of the combined surface,

an independent analysis is still required to ensure that the surface implementation is

correct and to help find any hidden problems.

Two possible methods of conducting the independent analysis is a beam by beam statistical analysis or by a surface difference (NOAA field units should refer to section

5.1.2.2.2 of the OCS Field Procedures Manual for more information). Other methods

may be used if approved in advance by the COTR or Atlantic/Pacific Hydrographic

Branch.

A surface difference can be conducted by creating a surface using only main scheme

data and comparing to a surface created from only crossline data. The surfaces used

to compute the difference should have at least the resolution defined in section 5.1.2.

For either method, the hydrographer shall make a general evaluation of the multibeam

crossline to main scheme agreement, and discuss the results in Section B of the Descriptive Report. If the magnitude of the discrepancy varies widely over the survey, the

hydrographer shall make a quantitative evaluation of the disagreements area by area.

The difference surface shall also be included in the final deliverables.

5.2 Lidar

5.2.1 Accuracy and Resolution Standards

Lidar follows the standards for multibeam see sections 5.1.1 and 5.1.1.1 for information

on accuracy and resolution standards for lidar.

5.2.1.1 Lidar Resolution Standards

Spatial resolution The hydrographer shall maintain and operate the lidar system,

from data acquisition to processing to detect hazardous features. As the spatial resolution (i.e., the spacing of the lidar footprint on the seafloor) is dependent on a wide range

of variables: 1) propagation of light through the water 2) the received signal strength 3)

the object detection algorithms used 4) changes in water depth, and 5) aircraft height

above the surface the actual bottom resolution may not remain constant. The hydrographer shall make a statement in the Descriptive Report describing the areas within

the survey where they are confident that the multibeam resolution standards defined

in section 5.1.1.2 are met (2x2x2m cube).

Spot spacing requirement will be defined in the Statement of Work, typically 3x3 or 4x4

at 200% coverage.

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5.2.1.2 Gridded Data Specifications In the Navigation Surface approach, survey

data are archived as a certified digital terrain model rather than as a set of verified or

certified soundings. The archived elevation model could be saved at the highest resolution supported by the sounding data. For example, if the laser spot spacing on the

seafloor of a full-coverage lidar survey is 3 meters, the elevation model could be saved

at a grid spacing of 3 meters. However, if environmental conditions (i.e. kelp, turbidity,

or sea state) create differences in data density an alternative approach may be discussed with the COTR and clearly described in the Descriptive Report (DR). This practice has the advantage of preserving this high-resolution data for a variety of known

and unknown future purposes, even if such resolution will never appear on a navigational or charting product. Charting products such as paper charts are created from

scale-appropriate generalizations of the elevation model. In reality, the final resolution

of the surface may be slightly coarser than “the highest resolution supported by the

sounding data” due to depth ranges, bottom topography and other variables.

The data density and resulting grid resolutions created shall be discussed with the

COTR during the project planning phase. Any deviations from the plan, project instructions or Specifications and Deliverables shall be discussed with the COTR and clearly

described in the Descriptive Report (DR) and Data Acquisition and Processing Report

(DAPR).

If in rocky nearshore areas, the least depths of many features in a relatively small area

fail to be preserved, see section 5.1.1.3 for more guidance. See also section 8.1.2 for

guidance on delineating and characterizing this rocky seabed area.

Uncertainty The Navigation Surface for lidar requires that each sounding have a horizontal and vertical uncertainty. The uncertainty value for the grid shall be the greater of

the standard deviation and the a prior uncertainty. To do this effectively, an error model

is needed for all systems supplying measurements to compute the sounding; including

the GPS sensors and anything else that contributes to the calculation of a sounding.

The hydrographer shall include a discussion in the DAPR on how the uncertainty was

computed on each individual sounding and how the uncertainty was computed on the

grid, with a justification for that methodology.

If a complete error model is not yet available to compute the TPU for each individual

sounding then the hydrographer may apply a single uncertainty value to all grid nodes

that reflect the vertical error budget for a given survey. Include a discussion in the

DAPR on how the uncertainty was computed with a justification for that methodology.

5.2.2 Coverage

The required spot spacing and survey coverage will be specified in the Hydrographic

Survey Project Instructions or Statement of Work.

The hydrographer shall obtain 200% coverage when required to do so in the Statement

of Work. In situations where poor water clarity and related environmental factors make

200% coverage impossible the COTR shall be notified. In addition the hydrographer

shall identify (textually and/or graphically) those areas where full coverage was not

obtained and/or further investigation using sonar may be required.

All soundings shall meet the accuracy requirements of Section 5.1.1.1. Grid resolutions

shall be appropriate for the spot spacing required in the Statement of Work.

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Complete lidar coverage

• Grid resolution shall nominally be 3 meters - If survey data can support higher

resolutions, then use hydrographer discretion and submit a higher resolution, if

appropriate.

• Maximum surface uncertainty is IHO Order 1 for depths less than 100 meters.

The hydrographer must ensure that accurate least depths are obtained on all significant

features. Individual soundings that do not meet the Horizontal Position Accuracy as

defined in Section 3.1 or do not meet the Vertical Accuracy as defined in Section 5.1.1.,

shall not be applied to the grid.

As always, the hydrographer must ensure that the data accurately reflects the condition of the seafloor at the time of the survey and adjust operations if required. Any

deviations from the specifications must be clearly explained in the Descriptive Report

and discussed with the COTR as they occur.

5.2.3 Corrections to Lidar Soundings

To meet the accuracy and resolution standards for measured depths specified in Section

5.1.1 and 5.1.1.1, and to create a BAG that includes an accurate uncertainty layer, the

hydrographer should conduct an error analysis of their survey systems.

Precise measurements are fundamental to the field of hydrography. Synchronization

of multiple sensors with the lidar system is essential for meaningful spatial analysis

of the data. All measurements, however careful and scientific, are subject to some

uncertainties. Error analysis is the study and evaluation of these uncertainties with the

purpose of estimating the extent of the uncertainties and when necessary, reducing

them.

In recognition of the possibility that some discrepancies in sounding may not be detected until the final processing phase of the survey, the determination and application

of corrections to soundings must be accomplished and documented in a systematic

manner. In addition, it is preferable that all corrections be applied in such a way that

the on-line values may be removed and replaced with a revised set of correctors during

office processing. Corrections to soundings are divided into five categories, and listed

below in the sequence in which they are applied:

Instrument error corrections account for sources of error related to the sounding

equipment itself.

Roll, pitch, heading, and navigation timing error (latency) corrections shall

be applied to lidar soundings to correct the effect of the aircraft’s motion caused by

turbulence, the error in the aircraft’s heading, and the time delay from the moment the

position is measured until the data is received by the data collection system (navigation

timing error).

The hydrographer shall also discuss (in Section B2. of the Descriptive Report) the methods used to quantify the survey systems error model. Uncertainty estimates for all

components of the sounding measurement should be provided.

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5.2.3.1 Instrument Error Corrections In modern digital sounding instruments,

instrument errors are generally small and of a fixed magnitude independent of the

observed depth. Proper set up and adjustment of Lidar equipment using internal checks

will often eliminate instrument error entirely. However, to ensure the proper operation

of the lidar system “confidence checks” shall be conducted periodically.

Frequent checks should be made between the overlap of main scheme and crosslines

collected on different days. These comparisons should be made frequently during data

collection to find errors promptly, and not saved until final data processing after the

field party has left the working grounds.

Any differences should be investigated, and if, after analysis, a corrector is necessary,

it should be applied with an explanation of the cause of the difference explained in the

Descriptive Report (DR) section B2., Quality Control.

5.2.4 Quality Control

5.2.4.1 Lidar Calibration Field calibration is performed by the system operator

through flights over a calibration site that has been accurately surveyed using GPS

or conventional survey techniques such as triangulation or spirit leveling. Typically,

the calibration site may include a large, flat-roofed building whose corners have been

accurately surveyed with GPS and a large, flat parking lot and runway. The calibration

may include flights over the site in opposing directions, as well as cross flights. The

field calibration is used to determine corrections to the roll, pitch, and scale calibration parameters. Field calibrations must be performed for each project or every month,

whichever is shorter.

Prior to commencing survey operations, the hydrographer shall conduct a system accuracy test to quantify the accuracy, precision, and alignment of the lidar system. Testing

shall include determination of residual biases in roll, pitch, heading, and navigation timing error and the uncertainty of these values. These values will be used to correct the

initial alignment, calibrate the lidar system and used in the computation of the Total

Propagated Uncertainty (TPU).

Once calibration data have been processed and final system biases determined, the

new corrections shall be used in a performance check to ensure that the new system

biases are adequate. The hydrographer shall discuss procedures and results in Section

A. Equipment and optional Section B. Quality Control of the project Data Acquisition and

Processing Report. Copies of all system alignment, accuracy, calibration reports, and

performance checks shall be included in the Data Acquisition and Processing Report.

System accuracy testing shall be repeated whenever changes (e.g., sensor failure,

replacement, re-installations, re-configurations, or upgrade; software changes which

could potentially affect data quality) are made to the system’s baseline configuration,

or whenever assessment of the data indicates that system accuracies do not meet the

requirements in Section 5.1.1 and 5.1.1.1.

5.2.4.2 Positioning System Confidence Checks Confidence checks of the primary positioning system shall be conducted and recorded in the survey records at least

once every week. A successful confidence check shall compare positions from the primary system to simultaneously observed check positions from a separate, independent

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system with a positional accuracy better than 10 meters. The inverse distance shall not

exceed 10 meters. If correctors for the primary positioning system are obtained from

a non-USCG differential system, then the check system must use correctors from a reference station different from the primary systems. If correctors are obtained from a

USCG differential station, the check system may use the same correctors as the primary system. The confidence checks shall be an integral part of the daily survey data

record. A summary report of positioning system confidence checks shall be included in

Separate I of “Separates to be included with the Survey Data” (see 8.1.3).

5.2.4.3 Crosslines

General The regular system of sounding lines shall be supplemented by a series of

crosslines for verifying and evaluating the accuracy and reliability of surveyed depths

and plotted locations. Crosslines shall be run across all planned sounding lines at angles

of 45 to 90 degrees. The preferred area in which to run crosslines is in an area of gently

sloping bottom.

The hydrographer shall make a general evaluation of the lidar crossline to main scheme

agreement, and discuss the results in Section B of the Descriptive Report. If the magnitude of the discrepancy varies widely over the survey, the hydrographer shall make

a quantitative evaluation of the disagreements area by area.

The lineal nautical miles of crosslines for lidar surveys shall be discussed and agreed

upon with the COTR during project planning. Under certain conditions (e.g., steep terrain, airspace restrictions, or relatively narrow band of coverage) crosslines may not be

possible. In such cases, a deviation from this requirement shall be requested from the

COTR and explained in the DR.

An independent analysis of the crossline and main scheme data shall be conducted. Although any crossline/main scheme disagreements should be obvious in the attributes

of the combined surface, an independent analysis is still required to ensure that the

surface implementation is correct and to help find any hidden problems. Include a

statement regarding the results of the comparison in Section B of the Descriptive Report. If created, the difference surface shall also be included in the final deliverables.

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6 Towed Side Scan Sonar

During hydrographic surveys, the use of side scan sonar may be required for supplementing echo-sounding by searching the region between regular sounding lines for

additional indications of dangers and bathymetric irregularities. Any requirement for

side scan sonar coverage in conjunction with a hydrographic survey will be specified in

the Hydrographic Survey Project Instructions or Statement of Work.

6.1 Coverage

Scanning coverage is the concept used to describe the extent to which the bottom

has been covered by side scan sonar swaths, that is, the band of sea bottom which is

ensonified and recorded along a single vessel track line. For hydrographic purposes,

scanning coverage of an area is expressed in multiples of 100 percent, and is cumulative. One hundred percent coverage results in an area ensonified once, and two hundred percent coverage results in an area ensonified twice. Advisory note: Side scan

coverage may not be achieved as planned due to varying water conditions, such as

thermoclines, limiting such coverage.

The scanning coverage requirements will be stated in the Hydrographic Survey Project

Instructions or Statement of Work. Approved 200-percent coverage techniques are as

follows:

Technique 1. Conduct a single survey wherein the vessel track lines are separated by

one-half the distance required for 100-percent coverage.

Technique 2. Conduct two separate 100-percent coverages wherein the vessel track

lines during the second coverage split the difference between the track lines of the first

coverage. Final track spacing is essentially the same as technique 1.

Technique 3. Conduct two separate 100-percent coverages in orthogonal directions.

This technique may be advantageous when searching for small man-made objects on

the bottom as the bottom is ensonified in different aspects. However, basic line spacing

requirements for single-beam echosounders may not be met when using this technique.

6.2 Side Scan Acquisition Parameters and Requirements

6.2.1 Accuracy

The side scan sonar system shall be operated in such a manner that it is capable of

detecting an object on the sea floor that measures 1 m x 1 m x 1 m from shadow length

measurements.

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6.2.2 Speed

The hydrographer shall tow the side scan sonar at a speed such that an object 1 m on a

side on the sea floor would be independently ensonified a minimum of three times per

pass.

The number of pulses per unit time, or pulse repetition rate, determines the speed at

which the transducer (i.e. the vessel) can move along the track and still maintain the

required coverage of the bottom. Longer operating ranges have slower pulse repetition rates, which requires the vessel speed to be slower if the entire bottom is to be

ensonified.

The maximum vessel speed for three ensonifications can be calculated if the pulse repetition rate (prr) or the pulse period (pp) is known. The rate is the reciprocal of the

period. This rate and/or period is usually published in the operating manual for the

side scan sonar system. The calculation is as follows: Maximum vessel speed (meters/second) = target size (meters) X prr/3 (sec-1).

6.2.3 Towfish Height

The hydrographer shall operate the side scan sonar system with a towfish height above

the bottom of 8 percent to 20 percent of the range scale in use. For any towfish height

below 8 percent of the range scale in use, the effective scanning range is defined to

equal 12.5 times the towfish height, provided adequate echoes have been received.

6.2.4 Horizontal Range

The achievable horizontal range of a side scan sonar is a function of several parameters.

Among these are sonar conditions, sea bed composition, the range scale in use, side

scan sonar system characteristics, and towfish height. Actual conditions in the survey

area will determine the effective range of a particular side scan sonar system. The

maximum allowable range scale for any towed side scan sonar is 100 m.

If the effective range scale of the side scan sonar is reduced due to external factors,

then the representation of the swath coverage should be reduced accordingly. For

example, changes in the water column or inclement weather may distort the outer half

of the 100 m range scale. In this case, only 50 m of effective range could be claimed.

6.3 Quality Control

6.3.1 Confidence Checks

Confidence checks of the side scan sonar system shall be conducted at least once daily.

These checks should be accomplished at the outer limits of the range scales being used

based on a target near or on the bottom. Each sonar channel (i.e., port and starboard

channels) shall be checked to verify proper system tuning and operation. Confidence

checks can be made on any discrete object, offshore structure, or bottom feature which

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is convenient or incidental to the survey area. Targets can include wrecks, offshore

structures, navigation buoy moorings, distinct trawl scours, or sand ripples.

Confidence checks can be made during the course of survey operations by noting the

check feature on the sonargram. If a convenient or incidental target is not available,

a known target may be placed on or near the bottom and used for confidence checks.

Confidence checks shall be an integral part of the daily side scan sonar operation and

shall be annotated in the side scan sonar data records.

6.3.2 Significant Contacts

In depths of water less than or equal to 20 m, contacts with computed target heights

(based on side scan sonar shadow lengths) of at least 1 m should be considered “significant.” In depths of water greater than 20 m, contacts with computed target heights

rising above the bottom at least 10 percent of the depth should be considered “significant”. Other contacts without shadows may also be considered “significant” if the

sonargram signature (e.g., size, shape, or pattern qualities) is notable. In addition, contacts with less than 1 m target heights should be considered “significant” if they are

found near the critical navigation depths of the local area. For example, if a 0.5 m contact is discovered in 10 m of water at the seaward approach to a dredged channel with

a controlling depth of 10 m, then the contact should be considered significant.

6.3.3 Contact Correlation

The hydrographer shall examine and correlate targets between successive side scan

sonar coverages (i.e., compare the first 100 percent with the second 100 percent sonar

coverage). If applicable, the hydrographer shall examine the multibeam data and correlate anomalous features or soundings with the side scan sonar data. Anomalous

features or targets which appear consistently and correlate in each type of data record

provide increased confidence that acquisition systems are working correctly and help

to confirm the existence of these features or targets. The hydrographer shall cross reference and remark on each target correlation in the Remarks column (column 7) of the

Side Scan Sonar Contact List (see Section 8.3.2).

6.3.4 Identification of Potential Field Examinations

The hydrographer shall use the sonar contact list, in conjunction with an analysis of

echosounder least depths and BAG attributes (standard deviation, uncertainty, etc), to

identify hydrographic features which may require further examination.

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7 Other Data

7.1 Bottom Characteristics

When required in the Hydrographic Survey Project Instructions or Statement of Work,

the hydrographer shall obtain samples of the bottom sediment. In general, the distance

between bottom samples should not exceed 1200 meters in charted anchorage areas,

and the distance between samples in all other areas should not exceed 2000 meters.

Bottom samples will not be required in depths greater than 100 meters. NOAA field

units should refer to section 2.5.4.2.1 of the Field Procedures Manual.

When sampling is required, the hydrographer shall record position and depth data for

each sample obtained. In addition, each sample shall be described and completely

attributed in the S-57 feature file. A table listing the position and description of the

bottom sample obtained shall also be included in Appendix V of the Descriptive Report.

7.2 Aids to Navigation

The hydrographer shall investigate all U.S. Coast Guard (USCG) and privately maintained fixed and floating aids to navigation located within the survey limits. Upon inspection of the most recent edition of the largest scale chart of the survey area and

the latest edition of the USCG Light List, the hydrographer shall confirm the aid’s characteristics and determine whether the aid adequately serves the intended purpose for

which it was established.

If the hydrographer determines that an aid to navigation is located off station, is damaged to the extent that it does not serve its intended purpose or its characteristics are

incorrectly charted, the facts should be reported immediately in the form of a danger

to navigation letter (see Section 8.1.2Danger to Navigation Report).

If an uncharted fixed or floating aid to navigation is discovered within the survey area,

the hydrographer shall obtain a differential GPS position on the aid and report the new

aid to navigation promptly to the nearest USCG district and submit a Danger to Navigation Report. Include geographic position, characteristics, apparent purpose, and by

whom the aid is maintained (if known).

Other fixed and floating aids to navigation and landmarks within the survey area may

require specific positioning methods. Positioning specifications and requirements will

be provided in the Hydrographic Survey Project Instructions/Field Procedures Manual or

Statement of Work.

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8 Deliverables

8.1 Field Reports

Reported horizontal positions shall be recorded in meters, with a precision of at least

decimeters (refer to section 5 regarding requirements for vertical (depth) positions).

This precision shall be maintained throughout the processing pipeline and be maintained in the digital data.

8.1.1 Progress Sketch and Survey Outline

The hydrographer shall report Monthly Survey Progress digitally via email as one Excel

file to progress.sketches@noaa.gov in accordance with the guidance below by the fifth

day of the month following survey operations. To assist in the submission of this information, N/CS31 will provide each ship and contractor with a Monthly Report Excel file

with separate tabs as indicated below. See example (Figure I.1) in Appendix 9.

a. Survey Progress Estimate – This will be used to track estimated monthly survey

progress by area within a given month. It will be a spreadsheet that consists of rows

showing the vessel’s current project and all associated survey sheets. Column titles

are self-explanatory. For each month that data is acquired on a survey sheet (as well as

sheets that are still incomplete) the cumulative percentage completed through the end

of that month should be entered in the spreadsheet. Any modifications to the initial

survey sheet layout must be reported.

b. Project Statistics – This will be used to track monthly statistics other than square

nautical miles. Since each row of the spreadsheet represents a specific project within

a given month, the field is advised to maintain one sheet for the entire fiscal year and

submit the updated version every month. The following provides clarification of the

columns within the spreadsheet:

• The “LNM VBES” (vertical beam echo sounder), “LNM MB” (multibeam), and “LNM

SSS’ (side scan sonar) are for the purpose of reporting operations using only one sonar

sensor. • The “LNM Combo” is for reporting LNM if a combination of sensors is used.,

such as side scan and single beam or multibeam and side scan. • The LNM above are

to be subdivided between ship and launch platforms as appropriate. • “Items Investigated” includes the number of AWOIS items or newly discovered items that require

extra survey time. • “Tide Gauges Installed/Removed” and “Bottom Samples” are the

only other stats needed from NOAA survey vessels. Contractors are still required to

report Days at Sea (on site working on the project) and days (or fraction of days) lost

due to weather or equipment malfunction.

c. Vessel Utilization – This is a requirement for NOAA vessels only. Refer to the Field

Procedures Manual, section 5.2.3.2.1 for details.

8.1.2 Danger to Navigation

As soon as practicable after discovery, the hydrographer shall submit a Danger to Navigation Report. Timeliness is a critical issue in reporting dangers to navigation. The

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hydrographer should ensure that the discovery of a potential danger to navigation is

reported immediately to the appropriate authority. Further, should additional dangers

be discovered during the processing of the survey, a danger report shall be immediately forwarded.

A danger to navigation is considered to be any natural feature (e.g., shoal, boulder,

reef, rock outcropping) as well as any cultural feature (e.g., wreck, obstruction, pile,

wellhead) which, during the course of survey operations was found by the hydrographer

to be inadequately charted as described below. Potential dangers shall be evaluated in

the context of the largest scale nautical chart of the area. Unless specified otherwise

in the Hydrographic Survey Project Instructions or Statement of Work, all submerged

features with depths of 11 fathoms (66 feet) or less in navigable waters should be

considered potential dangers to navigation and subject to reporting. During the course

of reviewing survey data for potential dangers to navigation, the hydrographer should

be aware of the types of vessels transiting the area along with usual and seasonal

vessel routes throughout the survey area.

Danger to Navigation Reports are required for:

• Significant uncharted rocks, shoals, wrecks, and obstructions

• Depths from the present survey which are found to be significantly shoaler than

charted depths or features, and are navigationally significant (typically depths of

11 fathoms (66 feet) or less)

• Uncharted or inadequately charted clearances for bridges and overhead cables or

pipelines

• A fixed or floating aid to navigation found to be off station to an extent that the aid

does not serve its purpose adequately

• A fixed or floating aid showing significantly different characteristics than those

charted or described in the Light List

• Other submerged or visible features, or conditions considered dangerous to surface navigation

Once all dangers to navigation (DTON) are identified by using the criteria above, they

must be reviewed in context with the largest scale chart covering the survey area.

DTONs submitted should include the date that the feature data was acquired and

should not cause undue clutter in relation to other soundings or features on the chart.

When multiple distinct features are located within 3mm of each other, as depicted on

the largest scale chart of the area, then the most significant DTON located within the

3mm radius shall be submitted as a single danger to navigation.

In cases where dangers are too complex to be adequately identified as discrete features, they should be appropriately depicted on a chartlet that accompanies the danger

letter. For example, widespread shoaling would be represented as a series of depths

with appropriate depth curves instead of listing individual soundings and geographic

positions. Danger submission shall include a chartlet that portrays the raster chart

and the Danger features. Include Multibeam and side scan imagery of the danger (see

Appendix 6).

NOAA field units shall use Pydro and submit all Danger to Navigation Reports via email directly to Marine Chart Division’s (MCD) Nautical Data Branch at e-mail address

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ocs.ndb@noaa.gov, with courtesy copies to Chief, Operations Branch and to the chief of

the appropriate Processing Branch, in accordance with section 4.4.4.6 of the OCS Field

Procedures Manual.

Contractors shall submit all Danger to Navigation Reports via e-mail to the COTR and

ACOTR at processing branch stated in the Statement of Work.

The contractor reports will be submitted as follows:

1. Letter in the format shown in Appendix 6 (Figure F.1 ) ,

2. An ascii text file of the format; ‘latitude, longitude, depth, feature, date, time’.

3. A chartlet showing the DTON on the largest scale chart of the area.

4. Screen captures of Side Scan Sonar or Multibeam image of the DTON.

The ACOTR will review the DTON, import the ascii file into Pydro, and create the .xml

file (ACOTR’s should see section 4.4.4.6 for more information). A letter and .xml file will

then be forwarded to the Nautical Data Branch at ocs.ndb@noaa.gov.

MCD will process the Danger to Navigation Reports and send the information to the

USCG for inclusion in the Local Notice to Mariners. MCD will notify the submitting party

of any changes made to the Dangers to Navigation Report by return e-mail. The Processing Branches will submit any dangers to navigation detected during office processing to MCD as stated above. If the Processing Branch is submitting a DTON that changes

an earlier DTON submitted by a field unit, please explain the change in the cover letter.

A copy of the Danger to Navigation Report shall be included in Appendix I of the Descriptive Report.

8.1.2.1 Charted Feature Removal Request Charted features, particularly “Position Approximate” wrecks and obstructions that are located in major shipping corridors

should be expeditiously removed from the chart if adequately disproved. The Charted

Feature Removal Request is similar to a Danger to Navigation Report, except it is used

to remove a charted feature that represents a hazard, which does not exist, rather than

add a newly found hazard. This process should be used sparingly, usually by responding

to a request from local pilots or other authorities that a charted feature is a hindrance

to operations. If removal of a feature is not time critical, utilize the descriptive report to

recommend removal from the chart rather than the Charted Feature Removal Request.

The Operations Branch, within the Hydrographic Surveys Division, is responsible for

defining the search criteria for all AWOIS items. If local authorities request the hydrographer to investigate a feature that has not been assigned, contact Operations Branch

for a determination of the search criteria. Once the hydrographer meets the search criteria and determines the feature does not exist, they should expeditiously prepare the

Charted Feature Removal Request and forward it to the appropriate Processing Branch

for verification. The format for the request is the same as a Danger to Navigation Report. The Processing Branch will review the request and, if the verifier concurs with the

hydrographer’s recommendation, will forward the request to the Marine Chart Division.

See Figure F.1 in Appendix 6 for an example of a Charted Feature Removal Request.

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8.1.3 Descriptive Report (DR)

A Descriptive Report is required for each hydrographic survey completed, unless specified otherwise in the Project Instructions or Statement of Work.

The primary purposes of a Descriptive Report are to: 1) help cartographers process

and evaluate the survey; 2) assist the compilers producing or revising charts; 3) document various specifications and attributes related to the survey and its by-products;

and 4) provide a legal description of the survey standards, methods, and results. The

cartographers will have no knowledge of the particulars of a survey, other than what

is documented in the Hydrographic Survey Project Instructions or Statement of Work,

digital survey data, Descriptive Report, and supplemental reports referenced in the Descriptive Report. The Descriptive Report is archived as a historical and legal record for

the survey.

The Descriptive Report supplements the survey data with information that cannot be

depicted or described in the digital data. The Descriptive Report describes the conditions under which the survey was performed, discusses important factors affecting the

survey’s adequacy and accuracy, and focuses upon the results of the survey. It contains required information on certain standard subjects in concise form, and serves to

index all other applicable records and reports.

General statements and detailed tabulations of graphically evident data, such as inshore rocks, shoals, or coral heads already shown in the S-57 feature file or compiled in

Pydro, should normally not be included in the Descriptive Report. Hydrographic characteristics of the survey area such as nearshore features, shoreline, currents, water

levels, and changes to the chart that are otherwise not clearly defined by the digital

products should be completely described in the Descriptive Report.

The following information is required in each Descriptive Report in the order listed below:

COVER SHEET (NOAA Form 76-35A, see Figure B in Appendix 2)

Appropriate entries are made to identify the survey. For each survey, the Registry

Number, Sublocality, General Locality, and State will be provided in the Hydrographic

Survey Project Instructions or Statement of Work.

TITLE SHEET (NOAA Form 77-28, see Figure C.1 in Appendix 3)

The “Hydrographic Title Sheet” is often referred to for information pertaining to the

survey. The “State”, “General locality”, and “Locality” entries are to be identical to

those on the Cover Sheet. The “Date of survey” entries are the inclusive dates of the

fieldwork.

For “Vessel”, enter the name and hull number of the surveying vessel. The name(s)

listed after “Surveyed by” are the personnel who supervised sounding operations and/or

data processing.

The “Remarks” section should contain any additional information, including the purpose

of the survey and survey area information that will identify the project or clarify the

entries above. Other Descriptive Reports or special reports containing information or

data pertinent to the survey that are not listed in Section E of the Descriptive Report

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text should be referenced here. Note the time zone used during data acquisition (e.g.,

All times are recorded in UTC). If applicable, list the name and address of the contractor

and any major subcontractors. If applicable, include the UTM zone number.

DESCRIPTIVE REPORT TEXT

A hard copy of the Descriptive Report (DR) need not be submitted. Two digital copies of

the DR shall be provided: in Microsoft Word format and Adobe PDF. The Microsoft Word

format shall be converted to an Adobe PDF file when the DR has been finalized and

shall have an approval sheet with a digital signature in accordance with section E.

The main body of the DR (sections A through E) shall be contained in a single file. Text

shall be Times New Roman, with a font size of 12. Include all information required for

complete understanding of the field records. When referring to a hydrographic feature

in the S-57 feature file, give the latitude and longitude of the feature. Discussions and

explanations should be written in a clear and concise manner. Avoid using geographic

names in the text of the Descriptive Report that do not appear on the nautical chart.

Avoid verbosity.

On each page of the DR body, include registry number and field unit as a header. Pages

shall be numbered consecutively from the first page of text, continuing through the

page preceding the Approval Sheet (page numbers as a footer, centered on page).

Include a Table of Contents with page numbers.

A. AREA SURVEYED

Include a coverage graphic inclusive of the survey area. The information related to the

present survey should be clearly shown and highlighted in some way to draw attention

to its location within the project area. A second small scale graphic should be included

if necessary to provide additional geographic context of where the survey is located.

List for each vessel (ship and/or launch number(s)) and the combined total of all vessels, the following information:

• Lineal nautical miles of single beam only sounding lines (main scheme only)

• Lineal nautical miles of multibeam only sounding lines (main scheme only)

• Lineal nautical miles of lidar sounding lines (main scheme only)

• Lineal nautical miles of side scan sonar only lines (main scheme only)

• Lineal nautical miles of any combination of the above techniques (specify methods)

• Lineal nautical miles of crosslines from single beam and multibeam combined

• Lineal nautical miles of lidar crosslines

• Lineal nautical miles of developments other than main scheme lines

• Lineal nautical miles of shoreline/nearshore investigation (total length of the inshore buffer line)

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NOTE: Any lineal nautical miles that are deleted for any reason should not be included

in the above statistics.

List for the total survey the following information:

• Number of bottom samples collected

• Number of items investigated that required additional time/effort in the field beyond the above survey operations (these can be either from dive operations or

obtaining a detached position but should not include items developed by sonar

only or items deconflicted by “observations” only)

• Total number of square nautical miles

• Specific dates of data acquisition (e.g. June 5-9,16-19,22,24, 2005)

B. DATA ACQUISITION AND PROCESSING

B1. Equipment

In this section of the Descriptive Report list by manufacturer and model number only

the major systems used to acquire survey data or control survey operations (e.g., single

beam sonar, multibeam sonar, side scan sonar, lidar system, vessel attitude system,

positioning system, sound speed system). Include a brief description of the vessel (e.g.,

length overall and draft). A detailed description of the systems used to acquire survey

data or control operations shall be included in the project-wide Data Acquisition and

Processing Report. See Section 8.1.4.1 for additional information.

Include in a narrative description, with figures when useful, of any deviations from the

vessel or equipment configurations described in the Data Acquisition and Processing

Report.

B2. Quality Control

Discuss the internal consistency and integrity of the survey data. State the percentage of crossline miles as compared to main scheme miles. Evaluate their general

agreement. If the magnitude of the discrepancy varies widely over the sheet, make

a quantitative evaluation of the disagreements by area. Explain the methods used to

reconcile significant differences at crossings, and give possible reasons for crossline

discrepancies that could not be reconciled. See section 5.1.4.3 and 5.2.4.3 for additional information.

Discuss the uncertainty values of the submitted CARIS generated surfaces (uncertainty

or CUBE) and/or BAG(s). Explain and/or justify any areas that have an uncertainty

greater than the IHO levels allowed as described in section 5.1.2and 5.2.2.

Evaluate survey junctions in this section. Junctions are made between adjoining contemporary surveys to ensure completeness and relative agreement of depths. List, by

registry number, scale, date, and relative location, each survey with which junctions

were made. Include a summary of each junction analysis. Explain methods used to

reconcile significant differences at junctions, and give possible reasons for junction discrepancies that could not be reconciled. Include recommendations for adjustments to

soundings, features, and depth curves, if applicable.

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Discuss sonar system quality control checks.

Discuss any unusual conditions encountered during the present survey which would

downgrade or otherwise affect the equipment operational effectiveness. Discuss any

deficiencies that would affect the accuracy or quality of sounding data. Document these

conditions; including how and when they were resolved.

Describe any other factors that affected corrections to soundings, such as sea state effects, the effect of sea grass or kelp, and unusual turbidity, salinity, or thermal layering

in the water column. Provide a brief discussion on how the sound speed instruments

(CTD, Moving Vessel profiler, Thermosalinograph etc.) were used and the frequency of

the SVP casts. If appropriate, describe how the survey area was zoned to account for

sound speed variations from differing water masses.

Discuss the specific equipment and survey methods used to meet the requirements for

object detection and coverage for different areas of the survey. Any deviations from

the specifications must be clearly explained in the Descriptive Report.

B3. Corrections to Echo Soundings

Discuss any deviations from those described in the Correction to Echo Soundings section of the Data Acquisition and Processing Report.

Discuss the results of any sounding system calibration (e.g. patch test) conducted after

the initial system calibration that affect the survey data and were not included in the

Data Acquisition and Processing Report. Comment on the reason a new calibration was

conducted.

B4. Data Processing

Discuss details of the submitted CARIS generated surfaces (uncertainty or CUBE) and/or

BAG(s). For instance, how many grids cover the survey area, what grid resolutions were

used, why were the different grid resolutions selected, how do the resolutions change

over the depth range of the survey, etc.

C. VERTICAL AND HORIZONTAL CONTROL

Include in this section of the Descriptive Report a summary of the methods used to

determine, evaluate, and apply tide or water level corrections to echo soundings on

this survey.

Describe how the preliminary zoning was determined to be accurate and/or describe

any changes made to the preliminary zoning scheme.

State the horizontal datum and projection used for this survey. Briefly discuss the control stations used during this specific survey. If USCG DGPS stations are used, only

list the station name in this section. Explain in detail any difficulties that may have

degraded the expected position accuracy.

See Section 8.1.4 for additional information to be provided in the project Horizontal and

Vertical Control Report. NOAA field units should also refer to section 5.2.3.2.3 in the

OCS Field Procedures Manual.

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D. RESULTS AND RECOMMENDATIONS

D.1 Chart Comparison

Compare the survey with all corresponding bathymetric products available (e.g. Electronic Nautical Charts (ENCs) and Raster Nautical Charts (RNCs)) to prove or disprove

any exceptional bathy features attained by the survey coverage. Identify the chart by

number, scale, edition number, and edition date. In addition, Notices to Mariners affecting the survey area which were issued subsequent to the date of the Hydrographic

Survey Project Instructions or Statement of Work and before the end of the survey must

be specifically addressed. Identify the last Weekly and Local Notices to Mariners compared to during the survey by notice number and date. Any Notice that prompts a chart

comparison item must be identified by its Notice to Mariners number and date.

There are two aspects of chart comparison: (1) general comparison between survey

depths and charted soundings and (2) detailed comparison between survey data and

charted shoals and potentially dangerous features. One method for accomplishing the

first is a comparison between the digital surfaces generated from the survey data and

the ENC using appropriate GIS software. Comment on the degree of general agreement

with charted soundings and discuss general trends, such as shoaling or deepening occurring in the survey area. List significant charted depths that have been disproved but

do not do a detailed evaluation of every charted sounding.

Greater effort is needed when conducting the detailed comparison between the survey

data and all charted shoals and potentially hazardous features. Describe the methods

of investigation and include least depths for significant changes. Contractors shall list

charted features not found during the present survey. NOAA units should reference the

Feature Reports section in the OCS Field Procedures Manual section 5.2.3.3.2 regarding

features protocol and/or the Notebook delieverables in section 5.2.3.3.2.1.

Discuss the methods used for both aspects of chart comparison in sufficient detail to

demonstrate that the chart comparison was accomplished adequately.

List and discuss comparisons of survey depths with controlling depths, tabulated depths,

and reported depths of all maintained channels. Also discuss soundings in designated

anchorages, precautionary areas, safety fairways, traffic separation schemes, pilot

boarding areas and along channel lines and range lines.

Briefly describe assigned Automated Wreck and Obstruction Information System (AWOIS)

items investigated by single beam or multibeam echosounder, side scan sonar, divers,

and/or other methods in this section. AWOIS Feature Reports should be placed in Appendix 2. Include an analysis of any differences between past and present survey

findings and make a specific charting recommendation. Also, include any official salvage documentation that would expunge the feature from the chart without having to

further investigate with a survey platform.

Any charted features that contain the label PA, ED, PD, or Rep (see Chart No. 1 for

definitions.), not specifically assigned as an AWOIS item and investigated in this survey,

should be documented and discussed in this section. The source of the charted feature

should be listed if known. Also, discuss features such as wrecks and obstructions from

miscellaneous sources. Describe the condition and distinguishing characteristics of all

items mentioned. NOAA units should reference the Pydro generated “For Descriptive

Report” feature report as necessary for this requirement (see section 5.2.3.3.2.2 of the

OCS Field Procedures Manual) and place the output reports in Appendix 2.

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Refer to any Danger to Navigation Reports submitted for this survey. A negative statement is required if no Danger to Navigation Reports were submitted.

D.2 Additional Results

If specified in the Hydrographic Survey Project Instructions or Statement of Work, describe and discuss the shoreline investigation results.

If applicable, briefly discuss prior survey comparisons conducted by the hydrographer.

In general, prior survey comparisons are not required by field personnel, but may be

used at the discretion of the hydrographer for quality control purposes. Prior survey

comparisons can be very helpful to the hydrographer both in the field and during final

data processing. Prior surveys may be obtained by contacting the appropriate Processing Branch or by contacting the COTR (if not already provided on the project CD).

Discuss aids to navigation which do not serve their intended purpose, are damaged, or

whose characteristics do not match the chart or Light List (see Section 7.2). A statement shall be made in this section of the Descriptive Report if all aids serve their intended purpose. NOAA units should refer to section 3.5.3.3 of the OCS Field Procedures

Manual and Hydrographic Survey Project Instructions for specific guidance on positioning aids to navigation.

List all bridges, overhead cables, and overhead pipelines. State the status or condition

of each feature. Provide applicable clearances determined by the survey party or by an

authoritative source (e.g., the U.S. Coast Guard or U.S. Army Corps of Engineers). Include the geographic coordinates directly below the minimum clearance point. All such

charted overhead features that no longer exist must also be listed. Include written documentation, if available, and photographs with the survey records. Invalid or uncharted

overhead clearance information, or ongoing construction of bridges or overhead cables

and pipelines, constituting a potential danger to navigation, should be reported to the

U.S. Coast Guard and the U.S. Army Corps of Engineers. Mention any submarine cables

and pipelines and any associated crossing signs on the shoreline. Include coordinates

for signage or the water entry point of the feature. Note ferry routes and list position

of each ferry terminal, if not shown on the chart or contemporary NOS remote sensing

maps.

For each drilling structure, production platform, and well head within the survey area

(excluding temporary jack up rigs), make a comparison between the new survey position and the largest scale chart on which the feature is shown and discuss any differences.

Provide information of significant scientific or practical value resulting from the survey.

Unusual submarine features such as abnormally large sand waves, shifting or migrating shoals, mounds, valleys, and escarpments should be described. Discuss anomalous

tidal conditions encountered, such as the presence of swift currents not previously reported. Discuss any environmental conditions encountered, which have a direct bearing on the quality and accuracy of the hydrographic data. If special reports have been

submitted on such subjects, refer to them by title, author, and date of preparation or

publication.

Mention present or planned construction or dredging in the survey area that may affect

the survey results or nautical charts. Recommend new surveys for any adjacent areas

that need them. As appropriate, include recommendations for further investigations of

unusual features or sea conditions of interest that go beyond routine charting requirements. Recommend insets to be shown on the published chart of the area, if requested

by chart users or needed for clarity.

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E. APPROVAL SHEET

The approval sheet with a digital signature shall be part of the digital DR file. It is

important to note that there is a distinct difference between a true digital signature

and a digitized signature. The latter is simply an image or other capture of a person’s

pen-and ink signature. By using a document scanner or an electronic pen capture

device, a person’s signature may be digitized. However, simply attaching this type of

signature to an electronic document is not the same as attaching a digital signature.

A digital signature, by contrast, appends a cryptographic “key” to the document that

can be used to verify the identity of the signer (authentication), ensure that no changes

have been made to the document since signing (integrity), and ensuring that the signer

cannot deny having signed the document (non-repudiation). Until such time as an

organization-wide digital signature solution is implemented, the nature of self-signed

digital signatures will limit authentication and non-repudiation capabilities of the system. The mechanism of applying the digital signature may include a digitized version

of a person’s signature, or it may not.

Use of the Adobe PDF format provides a standard vehicle for delivery of descriptive

reports. PDF supports digital signatures, and has been identified as an archive format

by the National Archives and Records Administration. The use of PDF combined with

digital signatures provides reasonable protection and assurance against inadvertent

document modification, as well as a means for tracking intentional document modification.

The approval sheet shall contain the following:

• Approval of the deliverable files, Descriptive Report, digital data, and all accompanying records. This approval constitutes the assumption of responsibility for the

stated accuracy and completeness of the hydrographic survey.

• A statement as to whether the survey is complete and adequate for its intended

purpose or if additional work is required.

• The amount and degree of personal supervision of the work.

• Additional information or references helpful for verifying and evaluating the survey.

List all reports and data not included with the survey records or Descriptive Report that

have been submitted to the processing office or to another office (e.g., Data Acquisition

and Processing Report, Vertical and Horizontal Report, Tides and Water Levels Package,

Coast Pilot Report). Include date of the report or date of submission.

If appropriate, other personnel responsible for overseeing or directing operations on

this survey sheet may also sign the Approval Sheet.

DESCRIPTIVE REPORT APPENDICES

The Appendices shall be submitted as a separate Adobe Acrobat file from the DR and

in a digital format only. NOAA units should refer to section 5.2.3.3.1 of the OCS Field

Procedures Manual for additional guidance on the content of DR Appendices.

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I. DANGER TO NAVIGATION REPORTS

Include copies of Danger to Navigation Reports and correspondence. List each document by some type of unique identifier, such as date for a letter or e-mail.

II. SURVEY FEATURE REPORT

Include a copy of all AWOIS item investigation reports and associated graphic correlation output. Include any official salvage documentation that supports an AWOIS charting recommendation. NOAA units shall meet this requirement by submitting the “For

Descriptive Report” feature report generated in Pydro as Appendix II.

The Feature Report for all features attributed as a wreck shall include an image of the

Side Scan Sonar contact and/or multibeam hits. This image will assist in the review for

significant underwater cultural heritage items.

III. FINAL PROGRESS SKETCH AND SURVEY OUTLINE

Include a copy of the final Progress Sketch and final survey outline that were submitted

as per the requirements in Section 8.1.1.

IV. TIDES AND WATER LEVELS

Include the following (if applicable):

• Field Tide Note (see section 4.2.2)

• Final Tide Note (see section 4.5.3) If Final zoning and approved water levels were

applied by the field unit, include the Final Tide Note in the DR Append V. The Final

Tide Note is the letter provided by COOPS.

• Abstract of Times of Hydrography (lists every day during which hydrography was

conducted and the start and end times hydrography was conducted each day)

• A copy of the “Request for Approved Tides/Water Levels” letter

• Any other correspondence directly relating to tides and/or water levels

V. SUPPLEMENTAL SURVEY RECORDS AND CORRESPONDENCE

Include any additional survey records not previously addressed in the Descriptive Report, Appendices or Separates (e.g., MapInfo tables) and a summary table of bottom

samples obtained (if applicable). Any letter or email correspondence relating to the

present survey should also be included. Contractors shall submit supplementary correspondence in a format that can be an easily read (e.g *.txt) such that it is not proprietary

to an email program.

SEPARATES TO BE INCLUDED WITH THE SURVEY DATA

The following “SEPARATES TO BE INCLUDED WITH THE SURVEY DATA” supplementing

the Descriptive Report shall be submitted with each survey. The Separates shall be

submitted as a separate Adobe Acrobat file from the DR and in a digital format only.

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NOAA units should refer to section 5.2.3.3.1 of the OCS Field Procedures Manual for

additional guidance on the content of DR Separates.

I. ACQUISITION AND PROCESSING LOGS

Include all acquisition and processing logs in digital format from the present survey.

Include positioning confidence checks and sounding system comparison checks.

II. SOUND SPEED DATA

In previous versions of this manual, a table was required which identified the specific

sound speed profiles used during the present survey. Now the requirement is to submit

a list that can be imported into a GIS for office verifiers to analyze the distribution and

frequency of the SVP casts. This deliverable should identify the positions and dates

of all casts used; the maximum cast depth; and the dates/times for which the profiles

were applied. CARIS users can fulfill this requirement with the submission of the SVP

data that is within the CARIS project. Contractors and NOAA field units should refer to

the location where the digital sound speed files are located, and include a directory

listing of the files.

A vessel with a Moving Vessel Profiler (MVP) may use thousands of profiles for a single

survey. In such cases, a table of each individual cast is not required. Instead, replace

the table with a brief discussion on how the MVP was used (frequency, which areas of

the survey, vessels and/or lines it was used, etc.) If individual casts were conducted as

well, those casts should be included in a table.

Include confidence check results. Include copies of sound speed profiler calibration report(s), if calibration occurred after submission of the Data Acquisitions and Processing

Report (DAPR).

III. HYDROGRAPHIC SURVEY PROJECT INSTRUCTIONS/STATEMENT OF WORK

Include copies of the Hydrographic Survey Project Instructions or Statement of Work.

Include all changes/modifications which apply to the survey being submitted.

IV. CROSSLINE COMPARISONS

Include the summary plot analysis as a function of beam number if conducted for the

main scheme/crossline intersections as required in Section 5.1.4.35.1.4.3 and 5.2.4.35.2.4.3,

if applicable. Include any other crossline quality reports required by the Hydrographic

Survey Project Instructions or Statement of Work.

V. SIDE SCAN CONTACT LISTING AND IMAGES OF SIGNIFICANT CONTACTS

Include the side scan contact listing, along with images of all significant contacts. Side

scan contacts are included as part of a normal Pydro data submission, which fulfills

this requirement. Non-Pydro users must submit significant contact images in a manner

which allows the Processing Branch to easily review and correlate specific contacts with

other supporting data sets.

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8.1.4 Descriptive Report Supplemental Reports

8.1.4.1 Data Acquisition and Processing Report The Data Acquisition and Processing Report (DAPR) is a project-wide report that shall be submitted before, or not

later than, the submission of the first survey of the project. For contract surveys, the

DAPR shall be sent to the COTR and appropriate Processing Branch specified in the

Statement of Work with each survey. For NOAA field units, the DAPR shall be sent to the

Chief, Hydrographic Systems and Technology Program (HSTP) and the appropriate Processing Branch specified in the Hydrographic Survey Project Instructions. This report

is separated into three sections: Equipment, Quality Control, and Corrections to Echo

Soundings. These sections shall contain a detailed discussion on the project specific

information addressed below.

A digital copy of the main text of the DAPR shall be provided in Adobe Acrobat format.

Include a cover sheet and title sheet which contain the following general information:

Cover Sheet. Include the type of survey(s), state, general locality and year (see Figure G.1 in Appendix 7).

Title Sheet. This contains additional descriptive information relative to the project. Include project number, date of Hydrographic Survey Project Instructions/Statement of

Work, vessel(s), field unit/contractor, sub-contractors, and Chief of Party/Lead Hydrographer.

A. Equipment

Describe the major operational systems used to acquire survey data or control survey

operations. Include the manufacturer, firmware version and model number, operational

settings and how the equipment was used. Include a description of the vessel(s) used.

Specifically discuss single beam, multibeam, lidar and side scan sonar systems and operations in this section. Include range scales, number of beams, resolution, along track

coverage, and quality assurance tools used during data acquisition. Include discussion

of other depth determination systems, such as, diver depth gauges, lead line, sounding

poles, etc. If applicable, explain the calibration or determination of correctors, the dates

of most recent calibrations, state whether or not checks were made on their accuracy

and describe any nonstandard procedures used.

Discuss the computer hardware and software used for all data acquisition and processing. Describe acquisition and processing methods, procedures, and parameters used.

Provide a complete list of all software versions and dates.

Include a description of equipment used to conduct shoreline verification. Briefly describe the method of conducting shoreline verification, including the processing of detached positions and depiction of shoreline features in the S-57 feature file.

B. Quality Control

Provide a description of the data processing routines for converting raw sounding data

to the final Navigation Surface grids. Include a description of the methodology used

to maintain data integrity, from raw sounding data to final soundings. Processing flow

diagrams are helpful. Any methods used to derive final depths such as cleaning filters,

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sounding suppression/data decimation parameters, gridding parameters, and surface

computation algorithms shall be fully documented and described in this section.

Discuss the methods used to minimize the errors associated with depth determination

and provide details of how the error models and TPU for each sounding is computed

(see Section 5.1.3.5(multibeam) or 5.2.1.2 (lidar)). Any deviation from this requirement

shall be explained here.

Discuss how under the navigation surface concept individual sounds are propagated or

combined into a node that is consistent with any specific object detection requirements

for the project.

Methods and standards used to examine side scan sonar records should be noted and

a brief description of processing procedures should be provided. Include the methods

for establishing proof of swath coverage and the criteria for selecting contacts. Additionally, include a brief description of how your review of digital side scan data meets

the object detection and accuracy requirements per section 6.2. The number of pixels

used to display digital side scan data on a computer is constrained by the width of the

display window and the screen resolution. Any compression method used in the review

of the side scan display must be discussed (e.g., whether an average or maximum pixel

intensity within a regularly-spaced acrosstrack interval X meters is used).

C. Corrections to Echo Soundings

This section addresses the methods used for the determination of all corrections to

echo soundings that apply to the entire project. Describe the methods used to determine, evaluate, and apply the following corrections to echo soundings, including the

uncertainties for each item:

• Instrument corrections

• All vessel configuration parameters, offsets, layback, etc include diagrams, pictures, or figures of the equipment as installed onboard

• Static and dynamic draft measurements

• Heave, roll, pitch biases, and navigation timing errors. State the manufacturer,

model, accuracy, and resolution of heave, roll, and pitch sensor(s). Discuss accuracy and alignment test procedures and results. Include copies of system alignment, accuracy, and calibration reports.

• Discuss the source of tide or water level correctors used for data processing and

final sounding reduction

D. Approval Sheet

The Chief of Party or Lead Hydrographer shall furnish a digitally signed statement of

approval for all information contained within the Data Acquisition and Processing Report

using the procedures prescribed in section E under the Descriptive Report Approval

Sheet.

If appropriate, other personnel responsible for overseeing or directing operations on

this project report may also sign the Approval Sheet.

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8.1.4.2 Horizontal and Vertical Control Report The Horizontal and Vertical Control Report is a project-wide report which shall be submitted before, or not later than,

the submission of the last survey in project area. NOAA field units should also refer to

section 5.2.3.2.3 in the OCS Field Procedures Manual.

A digital copy of the main text of the Horizontal and Vertical Control Report shall be

provided in Adobe Acrobat format.

Include a cover sheet and title sheet which contain the following general information:

• Cover Sheet - Include the type of survey(s), state, general locality and year.

• Title Sheet - This contains additional descriptive information relative to the project.

Include project number, survey registry numbers to which this report applies (with

associated dates of survey and locality), date of Hydrographic Survey Project Instructions/Statement of Work, vessel(s), field unit/contractor, sub-contractors, and

Chief of Party/Lead Hydrographer.

A. Vertical Control

The Vertical Control section of the project Horizontal and Vertical Control Report shall

document all Tide and Water Level activities that took place as part of this project. Specific information pertaining to an individual survey sheet and the Request for Approved

Tides letter shall be documented in the Descriptive Report for the individual survey.

This section shall contain a discussion of:

• All stations established by the field unit (include gauge model/type). Give station

number, latitude/longitude, and the dates/times of operation.

• The method by which correctors for the field data were obtained and applied.

• The time meridian used to annotate the tide records.

• A list of any unusual tidal, water level, or current conditions.

• The height and time corrections, and zoning if different from that specified in the

Hydrographic Survey Project Instructions or Statement of Work.

• Ellipsoidal benchmark positioning techniques and procedures

B. Horizontal Control

The Horizontal Control section of the project Horizontal and Vertical Control Report shall

document Hydrographic Position Control activities that took place as part of this project.

Specific information pertaining to an individual survey sheet shall be documented in the

Descriptive Report for the individual survey.

For horizontal control stations established by the field unit, describe the survey methods used to establish the station, and state the standards of accuracy used. Include

position accuracy plots (see Section 3.2.2). For all horizontal control stations established by the field unit, list:

• The latitude to at least the nearest 1/100th of a second.

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• The longitude to at least the nearest 1/100th of a second.

• The station elevation (ellipsoidal height).

• The geodetic station name and year it was established.

• Briefly, describe the methods and adequacy of positioning system confidence

checks.

C. Approval Sheet

The Chief of Party or Lead Hydrographer shall furnish a digitally signed statement of

approval for all information contained within the Horizontal and Vertical Control Report

using the procedures prescribed in section E under the Descriptive Report Approval

Sheet.

If appropriate, other personnel responsible for overseeing or directing operations on

this project report may also sign the Approval Sheet.

8.2 S-57 Feature File

The International Hydrographic Organization (IHO) Special Publication 57 (IHO S-57) is

the IHO Transfer Standard for Digital Hydrographic Data (current version is edition 3.1).

The IHO intends for the standard to be used for the exchange of digital hydrographic

data between hydrographic offices, and for the distribution of hydrographic data to

manufacturers, mariners and other data users. It was developed so that the transfer

of all forms of hydrographic data would take place in a consistent and uniform manner.

IHO Special Publication 57 may be downloaded free of charge at www.iho.shom.fr

Smooth sheets will no longer be required of Contractors or NOAA field units. The Processing Branches will use the S-57 feature file in conjunction with the BAG and other

survey deliverables to compile the survey data into navigational products.

The deliverables for a survey shall be:

1. Feature data for NOAA field units, feature data will be delivered via Pydro files,

and/or Notebook files as described in the Field Procedures Manual. Contractors

will deliver features compiled to a S-57 feature file.

2. A collection of Bathymetric Attributed Grids (BAG).

3. Metadata contained in the DR and associated reports.

NOAA field units may meet the features requirement using Pydro or Notebook deliverables (see section 4.4.9 and 4.10 of the OCS Field Procedures Manual)

The hydrographer shall submit BAGs at the highest appropriate resolution for the bathymetry

and feature detection requirements set in the Project Instructions. The BAG should be

in the NAD83 datum. The BAG should be UTM projected. The metadata for the BAG

shall include the NAD83 datum and UTM projection with the proper zone and resolution

of the grid. The S-57 feature file shall be in the WGS84 datum and unprojected.

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The S-57 feature file contains all the attributed information on specific objects that

cannot be portrayed in a simple depth grid. Features to include in the S-57 feature file

include; wrecks, obstructions, shoreline, rocks, islets, oil platforms, nature of seabed

(bottom samples) and all other objects that may need to be compiled to a navigational

product and require additional information that cannot be included in the BAG.

U.S. Coast Guard maintained aids to navigation shall NOT be included in the S-57 feature file. The hydrographer shall investigate all aids to navigation and report results

as required in section 7.2 and 8.1.4.1 Privately maintained aids and/or mooring buoys

should be included in the S-57 feature file, unless they are transitory.

The S-57 feature file shall include shoreline data only if the hydrographer conducted

shoreline verification. New features and changes to the source shoreline shall be portrayed in the S-57 feature file and be fully attributed.

General soundings, contours and depth areas will NOT be included in the S-57 feature

file since these objects will be derived from the final BAGs during chart compilation. In

rare cases, an isolated sounding may be part of the S-57 feature file if it needs a danger

circle and/or additional attributions.

8.2.1 S-57 Attribution

These Specifications and Deliverables will not attempt to include all possible objects

and attributions that may be required for a hydrographic survey. For a full reference

the hydrographer should refer to the resources described in section 8.2.

A list of the more common objects and attributions that may be used during a typical

hydrographic survey is given below. If the hydrographer has any questions on the appropriate attribution for an object, they should contact the COTR and/or the appropriate

Processing Branch for clarification.

All S-57 mandatory attributes for an object shall be completed. The hydrographer shall

attempt to provide as much additional information as possible on an object to facilitate

the Branches in final chart compilation of the survey. Whenever possible, additional information should be associated with the object itself. The attributes, INFORM, TXTDSC

and PICREP can be used to provide additional information. If it is not practical to communicate additional information using an attribute associated with the object, then the

hydrographer can provide the information using the DR, Item Investigation Report, Detached Position log (with photo), or other means.

All objects in the S-57 feature file must be properly attributed. S-57 feature file attributions can be divided into three broad categories; depths, features, meta-objects.

The most common items for each category and the related mandatory attributes are

described below.

ALL objects (depths, features and meta-objects), unless otherwise noted, will have

the attributes SORDAT and SORIND populated. For features that originate from an ENC

or raster chart, use the SORDAT and SORIND from that source. For other features:

SORIND (Source indication)

Format: ‘Country code, Authority code, Source, ID Code’. Example, “US,US,survey,H11393”,

if data came from a survey. Country (US), Authority (US for OCS), Source (survey), ID

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code (registry number). If feature is from RSD provided GC, the ID code becomes the

GC number, if the feature is carried forward from a chart or ENC the ID code is the chart

number (i.e. ‘chart 16707’).

SORIND Source Code Features File Source

survy For surveyed features: Bottom samples; Features with

heights or elevations (exposed rocks and wrecks, etc.)

obtained using rangefinder or similar device; Navigation

aids; Mooring buoys, Piles and dolphins; Shoreline

construction or other features gathered using portable

GPS device; Kelp or other observed features where no

discrete position was taken; Features digitized from

extents obtained by the field (ledges, reefs, piers and fish

pens, shoreline construction, etc.); Meta area objects.

nsurf For soundings, depth contours and depth areas from the

BASE Surface; For submerged rocks, wrecks, obstructions

and other features from the BASE Surface.

digit For digital map sources, such as GC shoreline.

graph Reserved for all features compiled to the Features file

from raster charts or ENC’s.

reprt Reserved for MCD’s use for letters, reports, NTM’s or

digital documents.

SORDAT (Source date)

Is the date associated with the SORIND above. For a hydrographic survey, it is the last

day of field operations. For a GC shoreline, the date the survey was flown, from the

metadata. From a raster chart, the chart date. From the ENC, it is the date that the ENC

has for the SORIND.

DEPTHS

Depth information is stored in three different forms, points (SOUNDG), lines (DEPCNT)

and Areas (DEPARE). The S-57 feature file will have all depth units in meters.

SOUNDG (Sounding)

A measured water depth or spot which has been reduced to a vertical datum (may be

a drying height). Soundings are bundled together by survey and share most attributes.

The number of soundings included is appropriate for the scale of the survey as defined

in the Statement of Work.

Mandatory Attributes:

• QUASOU (Quality of Sounding Measurement) - Generally set to ‘1’, for depth known.

• TECSOU (Technique of Sounding Measurement) – see table below

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Technique of Measurement for Height or Depth S-57 Attribute ID

Single beam echosounder (alone) ‘1’ if found by echo-sounder

Side Scan sonar (alone) ‘2’ if found by side scan sonar

Multibeam (alone) ‘3’ if found by multibeam

Diver depth ‘4’ if found by diver

Lidar (alone) ‘7’ if found by laser

Heights on rocks or islets using rangefinder ‘12’ if found by leveling

Navigation surface resulting from combinations of

sounding techniques, such as multibeam mixed with

single beam or side scan mixed with multibeam and/or

single beam (skunk-striping), or single beam or

multibeam mixed with lidar)

‘14’ computer generated

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FEATURES

All features should be attributed as fully as possible, with a few exceptions. Several

common features are listed below, followed by the mandatory attributes required for

them. Mandatory attributes for all features (WRECKS, UWTROC and OBSTRN) are listed

after the OBSTRN explanation. Do NOT attribute SCAMIN (Scale minimum) on any objects.

WRECKS (Wreck)

The ruined remains of a stranded or sunken vessel which has been rendered useless.

(IHO Dictionary, S-32, 5th Edition, 6027)

Mandatory Attributes:

• CATWRK (Category of Wreck) – For instance ‘1’ for non-dangerous wreck, ‘2’ for

dangerous wreck, ‘3’ for distributed remains of wreck, etc. or VALSOU (Value of

Sounding) - Least depth of the wreck.

UWTROC (Underwater/awash rock)

A concreted mass of stony material or coral which dries, is awash or is below the water

surface (See Rock Attribution Figure H.1 in Appendix 8)

OBSTRN (Obstruction)

In marine navigation, anything that hinders or prevents movement, particularly anything that endangers or prevents passage of a vessel. The term is usually used to refer

to an isolated danger to navigation... (IHO Dictionary, S-32, 5th Edition, 3503)

Mandatory Attributes for all features:

• TECSOU (Technique of sounding measurement) - Typically ‘1’ if found by echosounder, ‘3’ if found by multi-beam, ‘4’ if found by diver, ‘7’ if found by laser.

• QUASOU (Quality of Sounding Measurement) - Generally set to ‘1’, for depth known.

• VALSOU (Value of Sounding) – Least depth of the wreck.

• WATLEV (Water Level Effect) – For instance, ‘1’ for partly submerged at high water, ‘2’ for always dry, ‘3’ for always under water/submerged, ‘4’ for covers and

uncovers, etc.

SBDARE (Seabed area) Objects

The nature of bottom includes the material of which it is composed and its physical

characteristics. Also called character (or characteristics) of the bottom, or quality of

the bottom. (IHO Dictionary, S-32, 5th Edition, 515). The S-57 point object SBDARE is

typically used to report characteristics from bottom samples taken.

Mandatory Attributes:

Bottom characteristic objects will have one or the other or both of the following attributes (usually NATSUR):

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• NATSUR (Nature of surface) – Refer to S-57 library for codes, for instance, ‘1’ is

mud, ‘2’ is clay, ‘3’ is silt, ‘4’ is sand, etc.

• NATQUA (Nature of surface - qualifying terms) – Refer to S-57 library for codes, for

instance, ‘1’ is fine, ‘2’ is medium, ‘3’ is coarse, etc.

Where SBDARE is used to describe bottom characteristics obtained through bottom

sampling, NATSUR must be attributed. NATQUA is optional. Multiple characteristics

and qualifiers may be used. If a bottom sample was attempted but not achieved, use

NATQUA (hard). Where SBDARE is used to describe a rocky seafloor, NATSUR (rock) is

used.

SBDARE line or area objects may also be used to characterize areas of the seafloor that

are rocky in nature (See Section 5.1.1.3 for additional details regarding these areas). In

rocky nearshore areas, the least depths of many features in a relatively small area may

fail to be preserved, even by very high resolution BASE surfaces. In these instances the

hydrographer shall designate the least depths on the shoalest of features. The extents

of the area should then be delineated and characterized as SBDARE (seabed area), and

the attribute NATSUR (nature of surface) encoded as “rock”, as follows:

• NATSUR (Nature of surface) – ’9’ rock

• NATQUA (Nature of surface - qualifying terms) – (none)

SHORELINE

Shoreline information, if required by project, should be encoded in S-57 using the following feature objects and attributes.

COALNE (Coastline)

MHW line determined from bathy/topo data or geo-referenced orthophotos. COALNE

is attributed with CATCOA (Category of Coastline), if known. ELEVAT should not be

attributed for this object.

LNDARE (Land area)

A rock becomes an islet at 2 feet (0.6 meters) above MHW. LNDARE point, line or area

objects may be used to characterize islets (see “S-57 Encoding Guidelines for Rocks

and Islets for the Pacific Coast and Alaska”). LNDARE objects should be accompanied

by LNDELV point or line object, denoting the highest point of the feature.

LNDELV (Land elevation)

Elevation for islets is encoded using the object LNDELV, with attribute ELEVAT, which is

given relative to the MHW datum (taken from “S-57 Encoding Guidelines for Rocks and

Islets for the Pacific Coast and Alaska”).

META-OBJECTS

Meta-Objects provide metadata and additional information for large areas of the survey, or to attribute the entire survey area. The required meta-objects with their mandatory attributes are listed below.

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Areas of different coverage types should be separated and attributed using CATZOC

(Category of zone of confidence in data) according to the following table:

S-57 Attribute ID CATZOC Description

A1 Object detection multibeam

A2 100% multibeam coverage or 200% sidescan coverage

with skunk- striping using multibeam

B Single beam bathymetry or developments, or

skunk-striping using VBES (single beam) or Lidar alone

C Single beam lines for reconnaissance

U For features with heights obtained with methods other

than sonar, or where extents were collected for islets,

reefs, ledges, shoreline construction, etc.

• POSACC (Positional Accuracy, in meters) – For USCG beacons or other modern

Differential GPS systems, will typically be 10 meters.

• SURSTA (Start date of survey) - When compiling from a hydrographic survey, enter

the start date of the field operations in format, CCYYMMDD.

• SUREND (End date of survey) - When compiling from a hydrographic survey, enter

the end date of the field operations in format, CCYYMMDD.

• INFORM (Information) - Contains the Following String: Registry Number, Project

Number, and Contractor Name (H10934, OPR-D904-00, World Surveys Inc.)

M_COVR (Coverage)

A geographical area that describes the coverage and extent of spatial objects. The area

that comprises the compiled data or extents of survey.

Mandatory Attribute:

• CATCOV (Category of coverage) – ‘1’ for coverage available: continuous coverage of spatial objects is available within this area. ‘2’ for no coverage available:

an area containing no spatial objects (i.e. an area within the survey limits, not

addressed by the hydrographer.)

8.2.2 Cartographic Specifications and Conventions

Generalization of Features If the hydrographer determines an area unsafe, a foul

area can may be shown, but all available survey data that exists for any and all feature

objects will be included in the S-57 feature file (see the following sections regarding

rocky areas: 5.1.1.3 and 5.1.2 for multibeam data, 5.2.1.2 for lidar data and 8.1.2).

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Determination of the MHW Elevation A MHW value is required for compilation of

all Feature files containing shoreline or intertidal areas. It is used for defining DRVAL1

(Depth Range Value) attribute field for intertidal DEPARE’s where DRVAL2 will always

be 0.0. Example: -3.2 to 0.0 meters. Mean High Water (MHW) is the height of shoreline

above the sounding datum, MLLW. A MHW value is required for determining the height

at which a rock feature is depicted as an islet. This is now to be a measured value

using the most up-to-date and accurate tidal measurements for a survey area. For

NOAA field units this value should be taken from the CO-OPS Tide Note for Hydrographic

Survey, Height of High Water Above the Plane of Reference. For Contractors this will

be from the submitted Tide Report. When making estimated rock-islet determinations

before measured values are available, use the Mean High Water value, or if unavailable,

the Mean Higher High Water value, listed for the place nearest the survey area from

the TIDAL INFORMATION box on the RNC. Values may be interpolated between nearest

listed places. The ENC value for DRVAL1 (Depth Range Value) should not be used for this

purpose. The –h Mean High Water (MHW) value is used to populate the DRVAL1 (Depth

Range Value) attribute field for all intertidal DEPARE (depth area) features, including for

reefs and ledges. This value will be derived from the existing largest scale ENC covering

a survey area, if available or largest scale RNC if an ENC is not available. On ENC’s the

DRVAL1 attribute field is defined as MHW for intertidal DEPARE’s, always indicated by

a negative value, and DRVAL2 is defined as the offshore extent, always 0.0. If an ENC

covering the survey area exists, use the MHW (intertidal DRVAL1) value of the largest

scale ENC that covers the survey area. If no ENC exists, use the largest listed Mean

High Water value from the paper chart TIDAL INFORMATION box, or if no MHW category

is shown, use the largest listed Mean Higher High Water value.

Making the Rock-Islet Determination While the height parameters for making the

rock-islet determination have not changed, a new, easier to use formula has recently

been devised. Use absolute values for these calculations:

For Pacific Coast and Alaska

Any feature with a height < (MHW + 0.61m) is a rock; Attribute with VALSOU and

WATLEV. Any feature with a height >/= (MHW + 0.61m) is an islet. Attribute with

LNDARE and LNDELV where ELEVAT= (feature height) - (MHW).

For Atlantic Coast and Gulf of Mexico

Any feature with a height < (MHW + 0.31m) is a rock; Attribute with VALSOU and

WATLEV. Any feature with a height >/= (MHW + 0.31m) is an islet. Attribute with

LNDARE and LNDELV where ELEVAT= (feature height) - (MHW).

Rocky Areas Rather than encoding numerous discrete submerged UWTROC objects

in a relatively small area it is acceptable to delineate the extents of the rocky area,

using the Navigation Surface as a reference, then encode as an area object: SBDARE,

attribute: rock.

Rocks and Islets A rock will be depicted as an islet at 1 ft above MHW for Atlantic and

Gulf coasts, and 2 feet above MHW for Pacific and Alaska coasts. Only four of the seven

possible WATLEV categories will be used for equating VALSOU to WATLEV for rocks and

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islets. (See Rock Attribution Figure H.1 in Appendix 8, for use of S-57 attribution of rocks

and islets for Feature files.)

If applicable, the S-57 feature file should have the following parameters set;

• Producing Agency = US Office of Coast Survey,

• Navigational Purpose = 1 thru 5 according to chart compilation scale,

• Individual Cell Code = H number of survey, H12345 becomes ‘12345’,

• Horizontal Datum = WGS84 (datum of S-57 file),

• Vertical Datum (for heights) = MHW,

• Sounding Datum = MLLW,

• Units = metric

• Compilation Scale = survey scale,

• Coordinate Multiplication Factor = 10,000,000,

• Sounding Multiplication Factor = 1,000.

8.3 Side Scan Sonar

8.3.1 Side Scan Sonar Mosaic

A separate side scan mosaic for each 100 percent coverage shall be used as a graphic

means for demonstrating bottom coverage. Pixel resolution of the side scan mosaics

should be 1 m by 1 m. The hydrographer shall submit a digital file of each 100%

coverage (see Section 8.4.4).

If possible, the mosaics should be generated in one complete image file. If the survey

area is too large and/or creates a large image file that is unmanageable due to file

size, then the hydrographer shall subdivide the area into smaller more manageable

subsections. Contact the COTR and/or appropriate Processing Branch to discuss file

size limitations for each survey. However, do not create mosaics for individual side

scan line files.

8.3.2 Side Scan Sonar Contact List

Contact List

A Sonar Contact List of all contacts, both significant (Section 6.3.2) and insignificant,

are required and must include the specific elements of information which are described

below, along with a brief discussion of how each is to be derived. Specific entries may

vary by hydrographer. The format should be reviewed by the COTR and/or Processing

Branch before data collection is conducted.

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A digital copy of the contact list, ideally in spreadsheet format, shall be submitted with

the survey deliverables.

Column 1: Search Track Number—identifies the particular search track from which the

contact was observed.

Column 2: Contact Number—uniquely identifies the contact. An example of a contact

number is a number based on the date/time the contact was observed, followed by

a letter indicating the port or starboard (P or S) channel. For example, if a port-side

contact is observed on day 181 at 150125, the contact number will be 181/150125P.

Using signed (+ or -) contact range in column 4 eliminates the need for the P or S

indicator.

Column 3: Towfish Layback—the approximate distance in meters from the positioning

system antenna to the towfish. Unless computed by an automated system, the towfish

may be assumed to be directly astern of the towing vessel and on the search track.

Column 4: Contact Range—the horizontal distance from the towfish track to the contact, expressed in meters.

Column 5: Contact Position—the preliminary position as determined by reconstruction

of the vessel position, towfish layback, towfish position, port or starboard channel, and

contact range at the time the contact was observed. The Contact Position shall be

stated as a latitude/longitude (decimal degrees) or X/Y (easting, northing) values.

Column 6: Estimate of contact height computed from range and shadow length.

Column 7: Remarks—used to denote first impressions of the contact’s identity (e.g.,

wreck, rock, etc.), or to make any comments deemed appropriate. If, after examining

the records and correlating targets from overlapping coverage, the hydrographer determines that a contact does not warrant further investigation, it shall be noted as such.

A brief statement of the reasons must be made. Any abbreviations should be defined

on the list.

Column 8: Comparison with shallow water multibeam data—used to note the corresponding shallow water multibeam data (day/time, line number, etc.), the results of

comparing the side scan sonar data with the multibeam data (e.g., contact did not

appear in the multibeam data, swmb least depth = x.x—sss least depth = y.y).

Column 9: Contact is depicted in the S-57 feature file—answered in one of three ways:

(1) yes, obstr, (2) yes, sounding only or (3) no.

Once added to the list, a contact should never be removed. If, after further processing,

a contact is deemed not significant by the hydrographer, it shall be labeled as such

in column 7. The contact list, and any subsequent field examination lists and records

developed from the contact list, shall be included with the data submission in digital

form.

The contact list should be created such that it can be imported into a GIS for office

verifiers to analyze the distribution of contacts. However, if the hydrographer creates

any image files showing the distribution of contacts and/or other products to assist with

processing and analysis of the data, they may be included with the survey deliverables.

In some areas, significant contacts may be clustered (e.g., debris, boulder field). Such

an area may lend itself to being depicted as a single feature within the S-57 feature

file: a danger curve depicting the limit with accurately positioned least depth(s). If the

hydrographer has any questions to how the feature should be portrayed and attributed

within the S-57 feature file, they should contact the appropriate Processing Branch.

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Contact Images

For each significant contact in the contact list, the hydrographer shall provide an image

of the contact. Digital images shall be in a standard image format (e.g., tif, gif, jpg).

Copies of the images shall be included in the Separates, Section V. Digital file names

shall coincide with the contact name as depicted on the contact list.

8.3.3 Data Acquisition and Processing Abstracts

All sonargrams and data acquisition/processing comments shall be submitted digitally.

Time references shall be made in Coordinated Universal Time (UTC).

The hydrographer shall have a system to clearly indicate the status of the side scan

acquisition system. Historically, this was accomplished by annotating the paper sonargram as the data was being collected. Further annotations could be made during field

and/or office review of the sonargrams. Modern survey systems acquire the data digitally, therefore, separate data acquisition/processing logs may be used to record the

needed information.

The following comments (or annotations) shall be made in a manner that they can be

correlated by time or other method back to the digital side scan sonar record.

System-Status Annotations

System-status annotations are required to describe the recorder settings and the towing situation. System-status annotations shall include:

• Mode of tuning (manual or auto).

• Range-scale setting.

• Operator’s name or initials.

• Length of tow-cable deployed (tow point to towfish).

• Depressor in use (yes or no).

• Weather and sea conditions.

System-status annotations shall be made:

• Prior to obtaining the first position of the day.

• While on-line, whenever the system set up or status changes.

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First Position/Last Position Annotations

The following annotations shall be made at the first position on each survey line:

• Line begins (LB) or line resumes (LR).

• Tow-vessel heading (degrees true or magnetic).

• Towing speed (engine rpm, and pitch if applicable).

• Index number and time (at event mark).

The following annotations shall be made at the last position on each survey line:

• Line turns (LTRA, LTLA), line breaks (LBKS), or line ends (LE) index number and

time (at event mark).

Special Annotations

The occurrence of any of the following events shall also be annotated:

• Change in operator (new name or initials).

• Change in range-scale setting.

• Confidence checks.

• Individual changes to recorder channel settings.

• Change in tow-cable length (tow point to towfish).

• Change in towing speed (engine rpm and pitch) or vessel heading.

• Change in tow point.

• Significant contact observed.

• Surface phenomenon observed (wakes, passing vessels, etc.).

• Passes by buoys or other known features within sonar range (identify object).

• Interference (state source if known).

• Time corresponding to the index marker.

The hydrographer shall make any other annotations necessary to note any occurrence

which may later serve to reconstruct the operation. Too much information is always

better than not enough.

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Annotation Methods Header and system-status annotations may be made using

any of the following methods:

• By use of an automatic annotator, if available.

• Typed entries in the data acquisition system.

• Typed entries in a separate annotation file.

The method is left to the hydrographer’s discretion, but should be used consistently

throughout the operation.

8.4 Digital Data Files

The survey data will be supplied in a digital format. Hard copy plots and hard copy

printouts of reports are no longer required.

This section is provided as a summary for the major digital deliverables that may be

required for a typical hydrographic survey. Not all sections will apply to all surveys. For

both single beam and multibeam data, Contractors should separate digital deliverables

into two data types: raw and processed. Raw should be uncorrected or with exception

of online corrections. Processed data should include the Caris HDCS format or GSF.

NOAA units should refer to Chapter 5 of the OCS Field Procedures Manual for specific

format and other guidance pertaining to survey deliverables.

8.4.1 Media

Digital data shall be submitted on USB hard drives. Each registered survey shall be

submitted on a separate USB drive unless prior agreement is obtained from the COTR

or Processing Branch. The hydrographer shall include a directory listing of each drive,

or other method to enable the Processing Branch to determine where specific data

sets are located. Other formats may be allowed if agreed upon in advance with the

appropriate Processing Branch. The hydrographer shall work with NOAA to ensure no

compatibility problems exist after data submission.

Network Attached Storage Units, specifically MaxAttach or equivalent may also be used

to submit data. The hydrographer should contact the appropriate Processing Branch

ahead of time to determine proper shipping methods, directory structure and reach

agreement on when (or if) the Processing Branch will return the device.

8.4.2 Single-beam Data

The single-beam data format will be specified in the Hydrographic Survey Project Instructions or Statement of Work. Typically, the data will be submitted in a CARIS HIPS

compatible format with a final BAG at a 5m resolution.

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8.4.3 Shallow-Water Multibeam and Lidar Data

The hydrographer’s multibeam data format shall provide complete traceability for all

positions, soundings, and correctors including sensor offsets, biases, dynamic attitude,

sound speed, position, sensor position, date and time, vertical datum reducers, and

sounding data from acquisition through postprocessing. Data quality and edit flags

must be traceable.

Full Resolution Multibeam Data

The hydrographer shall submit full resolution multibeam data in a format readable

by CARIS HIPS (Version 6.1, by CARIS). Full resolution multibeam data shall be delivered fully corrected for tides, sound speed, vessel offsets, draft and dynamic draft.

These corrections may be made within CARIS, with data submitted as a complete CARIS

project (including HDCS files, sound speed files, Vessel Configuration, CARIS tide files,

etc.). Contractors that process with Caris, shall submit the fieldsheet directory so that

re-computation could occur if necessary.

Or the data may be submitted fully corrected, such that it will be read in CARIS HIPS

using a ‘zeroed’ Vessel Configuration file (.vcf or .hvf) and a ‘zero’ tide file (.tid), etc.

Full resolution data are defined as all data acquired and logged during normal survey

operations. Information and specifications on CARIS HIPS and data formats may be

obtained from CARIS at 506-458-8533.

Full Resolution Lidar Data

The contractor shall submit the full resolution lidar data in CARIS compatible format

(Version 6.1, by CARIS). The submission will include the appropriate CARIS converter,

lidar data before conversion, and all necessary CARIS files so that NOAA can reconvert

all files, if desired. Contractors that process with Caris, shall submit the fieldsheet

directory so that re-computation could occur if necessary.

CARIS BASE Surface and/or BAG

The final depth information from the survey will be composed of a collection of grids.

This collection of grids must reflect the state of the seafloor at the time of the survey.

The finalized uncertainty of the grids shall be the greater of the standard deviation

and a prior uncertainty. The hydrographer must take steps to ensure that all data

has been correctly processed and that appropriate designated soundings have been

selected (see section 5.1.1.3, 5.1.2 and 5.2.1.2). The collection of grids representing

the final reviewed results of the hydrographic survey shall be submitted as CARIS BASE

or BAG surfaces. NOAA field units typically process hydrographic data using CARIS HIPS

software. CARIS’ format for the Navigation Surface is a Bathymetry Associated with

Statistical Error (BASE) surfaces, either an Uncertainty or CUBE Surface. Non-CARIS

users may submit their Navigation Surfaces as a Bathymetric Attributed Grid (BAG).

The grids shall have a sequential naming convention, such as H12345_1_of_5.BAG,

H12345_2_of_5.BAG, H12345_3_of_5.BAG, etc.

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Specific Multibeam Data

The hydrographer shall submit data used for determining navigation time latency, pitch,

roll, and yaw biases in a separate directory on the submitted drive. The data format

shall be such that CARIS HIPS can convert the data, thus making it compatible as described earlier in this Section.

8.4.4 Side Scan Sonar Data

The hydrographer shall submit digital side scan data in a format readable by CARIS

SIPS (version 6.1, by CARIS, phone: (506) 458–8533). Digital side scan sonar shall

be geocoded using the towfish position (towfish position corrected). Information and

specifications on CARIS SIPS and data formats may be obtained from CARIS.

Side Scan Contact Images

The hydrographer shall submit digital images of all significant side scan contacts within

the contact list (see Section 8.3.2). Digital images shall be in a standard image format

(e.g., .tif, .gif, .jpg). The file name shall coincide with the contact name as depicted on

the contact list.

Side Scan Mosaics

The hydrographer shall submit a digital image file for each 100 percent coverage. The

digital image file shall be in a standard geo-referenced image format (section 8.3.1).

Contractors that process with Caris, shall submit the fieldsheet directory so that recomputation could occur if necessary and include the referenced image file.

8.4.5 Other Data

Tide and Sound Speed Data

The hydrographer shall submit tide data and sound speed data applied to all multibeam

depths on the project data drives. The hydrographer shall identify the data format and

all data element descriptions (e.g., ASCII text file or Excel spreadsheet file; date/time

referenced to UTC, tide relative to MLLW datum to the nearest centimeter). All tide data

required by 4, shall be sent directly to the appropriate CO-OPS office.

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Vessel Configuration File

The hydrographer shall submit a CARIS HIPS compatible HIPS Vessel File (HVF) for each

vessel used during survey operations. CARIS-compatible HVF shall contain those static

and dynamic correctors, offsets and uncertainties which are to be applied to the “Full

Resolution Multibeam Data” set submitted as referenced in Section 8.4.3 If the data

is submitted fully corrected with uncertainties already associated with each sounding,

then the CARIS HVF may be “all zeros”. In such a case, the hydrographer must provide

details on what values were derived for all the static and dynamic correctors, offset

and uncertainties and other information that is usually contained within a HVF in the

DR and/or DAPR. Information and specifications on the HVF format may be obtained

from CARIS.

Metadata

The following reports shall be included on the submitted data drive in a clearly labeled

directory;

• The main body of the Descriptive Report in Microsoft Word format.

• The Appendices and Separates to the DR in Adobe Acrobat .PDF format.

• The Data Acquisition and Processing Report in Adobe Acrobat .PDF format.

• The Horizontal and Vertical Control Report in Adobe Acrobat .PDF format.

S-57 Feature File

The S-57 feature file shall be included on the submitted drive in a clearly labeled directory.

Supporting Data

• Any associated text or image files to support S-57 feature file objects.

• Other interim data products that may help the Processing Branch verify the survey

and understand the pipeline from acquisition to final product.

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A Appendix 1: Tide Station Report and Next Generation Water Level Measurement System Site Report

Figure A.1: NOAA Form 77-12 Tide Station Report

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Figure A.2: Tide Station Report(cont.)

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Figure A.3: Tide Station Report(cont.)

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Figure A.4: N/OMA121 Form 91-01 Next Generation Water Level

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Figure A.5: Next Generation Water Level (cont.)

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B Appendix 2: Descriptive Report Cover Sheet (NOAA

Form 76-35A)

Figure B.1: Descriptive Report Cover Sheet(NOAA Form 76-35A)

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C Appendix 3: Descriptive Report Title Sheet (NOAA

Form 77-28)

Figure C.1: Descriptive Report Title Sheet (NOAA Form 77-28)

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D Appendix 4: Abstract of Times of Hydrography for

Smooth Tides or Water Levels

Figure D.1: Abstract of Times of Hydrography for Smooth Tides or Water Levels

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E Appendix 5: Example Request for Smooth Tides/Water

Levels Letter

Figure E.1: Example Request for Smooth Tides/Water Levels Letter

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F Appendix 6: Danger to Navigation Report

Figure F.1: Example of Danger to Navigation Report

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Figure F.2: Example of Chartlet to Accompany Danger to Navigation Report

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G Appendix 7: Data Acquisition and Processing Report

Figure G.1: Data Acquisition and Processing Report

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H Appendix 8: Rock Attribution

Figure H.1: Rock Attribution

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I Appendix 9: Statistics Spreadsheet Example

Figure I.1: Statistics Spreadsheet Example

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