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THE GRAND CANYON MONITORING RESEARCH CENTER

SURVEY PROTOCOL EVALUATION PROGRAM

FINAL REPORT

OF THE PEER REVIEW PANEL

Submitted by 

Raad Saleh, Ph.D. 

Chairperson, Peer Review Panel

Panel Members:

Dale Chayes 

Columbia University 

Jon Dasler 

David Evans and Associates, Inc. 

David Doyle 

National Geodetic Survey 

Richard D’Sanchez 

U.S. Geological Survey 

Michael Renslow 

Spencer B. Gross, Inc. 

John Rose 

Maricopa County Department of 

Transportation, 

Raad Saleh 

S&J International 

May 15, 2003
 

 

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EXECUTIVE SUMMARY 

DEFINITION 

This document reports the findings of the peer review panel commissioned by the Grand 

Canyon Monitoring Research Center (GCMRC) for the Survey Protocol Evaluation Program 

(PEP). 

PURPOSE OF THE PANEL 

The mandate of this Panel is to assist GCMRC in identifying optimum design and procedures 

for implementing an efficient and effective survey program that supports long-term 

monitoring of natural and cultural resources in the Colorado River Ecosystem (CRE). The 

peer evaluation process includes four specific tasks: 1) reviewing the technology, equipment, 

and methodology applied by GCMRC; 2) introducing new technology to reduce the impact of 

scientific field work in the Canyon corridor; 3) examining spatial data collected by GCMRC 

to ascertain whether user needs are being met; and, 4) recommending alternatives. 

SCOPE 

The scope of this mission includes review of terrestrial and hydrographic survey data 

collection methods and processing, data archiving, accuracy requirements and error 

determination, quality control and quality assurance, documentation and record keeping, 

spatial data standards, and survey control networks for both conventional (land based) and 

remotely sensed (airborne) survey data collection. 

The scope further includes requirements for spatially referencing and assessing aerial 

acquisition and other remotely sensed data sets. The review also covers requirements for 

automated spatial data processing methods using a geographic information system, image 

processing, and softcopy techniques for mapping and change detection of natural and cultural 

resources. 

In addition, since the impact of science in the Grand Canyon is a main concern, GCMRC 

aims at expanding the geographic extent of monitoring in a least impacting, yet in a cost 

effective manner. Therefore, the scope extends to review of the acquisition and processing 

protocols of aerial and other remotely sensed data sets intended for seamless integration with 

land-based survey data. 
 

 

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OVERVIEW 

Members of the Panel represented a variety of specialized and overlapping expertise relating 

to the review objectives. A listing and contact information of all panelists is found in 

Appendix I. 

The protocol review process consisted of four parts: 1) pre-review orientation and application 

descriptions, 2) on-site assessment of the operation area including a river trip from the Glen 

Canyon Dam to Lee' s Ferry, 3) technical briefing session, and 4) group discussion and 

drafting of report. 

At the pre-review orientation, the Panel was briefed on the various applications within the 

GCMRC mandate where survey data sets are exploited. The objective was to assess whether, 

or not, the spatial requirements of the data sets are being met with respect to these 

applications. 

The field trip allowed the Panel to closely observe some of the most dramatic and difficult 

areas within the CRE where most of the surveying activities were conducted. The Panel had 

the chance to see and hear about current research and monitoring studies and observe first 

hand the issues surrounding mapping and spatial referencing data collected in the ecosystem. 

The technical briefing session included several presentations on specific surveying activities, 

protocols, and practices at the GCMRC. The presenters and other staff members were 

queried by the Panel and asked to provide clarifications and further information. 

The Panel met privately the next day and reviewed the information from the field trip, written 

material, briefings, and presentations. A general discussion helped shape an overall 

assessment of the survey operations, strengths and weakness, and general recommendations. 

The submitted written questions were then addressed systematically, and Panel members with 

pertinent expertise helped answer them. The answers have been compiled and documented in 

this report. 

ORGANIZATION OF THE REPORT 

The report is divided into two parts, I and II. These two parts are based on the set of 

questions submitted by GCMRC to the Panel, as shown in Appendix II. The first part 

consists of 11 questions, and the second of 7 questions. Most of the questions have subquestions. The Panel addressed each of the questions and sub-questions with direct answers, 

findings, and recommendations. In addition, pointers and links to references and external 

reports were provided. Summaries of the findings and recommendations are listed in the 

executive summary. 

The report has four appendices. Appendix III documents email communication between 

GCMRC and USGS regarding advice on most appropriate coordinate system to use. 

Appendix IV lists abbreviated terms used throughout the report. 
 

 

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FINDINGS 

The findings of the panel are summarized below under each category. 

Terrestrial Surveying: 

• Current control networks, documentation, and collection protocols cannot be generalized 

as adequate at all scales, accuracy requirements, and project specifications. 

• Control points locations are not adequate for vertical measurements. 

• Although the local geoid requires improvement, its impact on accuracy may not constitute 

a high priority considering the cost-benefit aspects. 

• Datum conversion between National Geodetic Vertical Datum of 1929 (NGVD 29) and 

North American Vertical Datum of 1988 (NAVD 88) may not achieve high accuracy 

because of the lack of sufficient National Spatial Reference System (NSRS) benchmarks 

in the region. 

Aerial Surveying: 

• GCMRC provides adequate scope of work (SOW) to airborne surveying contractors. 

• Capabilities and resources are not currently compatible to make full use of the historical, 

near future, and mid-future photographic acquisition missions. 

• Current online and offline archiving capabilities are severely inadequate to support highvolume aerial and remote sensing operations. This issue will become even more 

problematic if historical photography is to be converted into digital files. 

• Specifications for aerial and remote sensing data are deficient, particularly in relation to 

the requirements of the intended application. This is especially critical since it impacts 

the cost of: acquisition, processing, and dissemination. 

Hydrographic Surveying: 

• The panel found that equipment, methods, and protocols for hydrographic surveying were 

adequate and meet accepted survey practices based on what was available for review. 

The exceptions are the heading sensor and survey documentation. 

• In the panel’s opinion, the current heading sensor is not adequate and other heading 

sensor options should be considered. 

• In the panel’s opinion, it is likely that the present attitude sensor technology utilized by 

GCMRC will result in heave artifacts under some lateral motion circumstances. 

• The panel cautions that automated statistical filtering techniques may eliminate actual 

data that are helpful in the analysis of anomalies and true bottom detection. One potential 

result is mapping the top of aquatic vegetation instead of the seabed. 

Standards and Specifications: 

• Adherence to declared standards is not consistent, nor is there established protocol to 

verify adherence to accuracy specification. In the panel’s opinion, this represents a 

serious flaw that, in extreme cases, may render the delivered data useless. 

• The Panel found no specific documentation of quality assurance / quality control 

(QA/QC) procedures, as well as no error determination protocols that apply, adequately, 

to any of the of survey categories. 
 

 

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• The Panel found no established procedures to ensure consistency among staff. Such 

consistency becomes critical especially when SOW, specifications, data, and procedures 

were communicated among various organizational units of GCMRC.

Staffing and Outsourcing: 

• Contracting of a surveying mission, end-to-end, has the potential of improving the ability 

of GCMRC to achieve its stated goals. Because of specific factors, this issue needs 

careful consideration and assessment of its efficacy. 

• GCMRC is at serious risk because of the size of its surveying staff. Very few individuals 

have intimate knowledge of all unique procedures, specifics of surveying projects, and 

other vital information on all aspects of spatial referencing of the area. 

RECOMMENDATIONS 

Terrestrial Surveying: The Panel recommends:

Establishing, in critical experimentation areas, sets of GCPs that satisfy certain 

specifications of inter-visibility, access, and link to Global Positioning System 

(GPS). 

• Coordinating with the National Park Service (NPS) and the Federal Geodetic Control 

Subcommittee to place new monuments and preserve existing control points. 

• Evaluation of the effects of varying geoid undulations on accuracy and its economical 

impact; and, if justified, cooperation with the National Geodetic Survey (NGS) and the 

U.S. Geological Survey (USGS) to improve the geoid locally. 

• Using North American Datum of 1983 (NAD 83) and NAVD 88 as the vertical datum. 

• That all equipment undergoes regular testing, adjustment, and calibration according to 

established schedules and procedures. 

Aerial Surveying: The Panel recommends that:

Numerical, quantifiable, and other descriptive specifications, including the 

number and distribution of ground control points (GCPs), be defined in 

conjunction with the intended project goals, and such specifications be 

incorporated into all future requests for proposals. 

• GCMRC expand its in-house photogrammetric and image analysis capabilities. 

• Where practical, airborne integrated GPS and integrated measurement unit (IMU) should 

be used in all aerial and remote sensing coverage to reduce the GCP requirements for 

photogrammteric processing. 

• More detailed specifications stipulating the methods, technologies, and accuracy 

standards employed in the aerial acquisition. 

• Storage, archiving, and networking needs be evaluated based on the volume requirements 

of post-conversion softcopy processing of historical photography. 
 

 

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Hydrographic Surveying: The Panel recommends: 

• the use of a multibeam sonar system with wider angular swath width (e.g., 150 degrees) 

to allow better coverage in shallow water and increase shoreline mapping capabilities, 

• that detailed patch test results be included in each survey report, 

• careful analysis of the dynamics of the survey platform (from existing navigation, 

bathymetry and attitude data) be performed; and a comprehensive error budget be 

developed for the survey system, 

• conducting careful evaluation of potential sensors upgrades, including field trials and 

subsequent analysis. 

• that automated statistical analyses be conducted with extreme caution. 

• Proper reporting of: processing methods, technical data, and tests results; and improving 

documentation of confidence checks. 

Standards and Specifications: The Panel recommends: 

• conformity with the latest national standards for geospatial positioning accuracy, in terms 

of reporting methodology, control networks, and specifications. 

• strict adherence to systematic and detailed documentation of meta data. 

• establishing appropriate QA/QC procedures for each of the four survey categories. 

• that contractors and subcontractors submit their QA/QC procedures specifically used to 

realize the contracted specifications. 

• establishing internal verification and validation protocols, including methodology, 

equations, checkpoints, and certification; and that GCMRC staff, or an independent third 

party, verify adherence to these protocols in internal as well as contracted work.. 

Staffing and Outsourcing: The Panel recommends: 

• doubling the number of permanent surveying staff, and adding part time geodesist. 

• knowledge of the area be systematically documented, archived, and disseminated within 

other GCMRC groups. 

• developing contingency plans to minimize the risks of staff relocation, downsizing, and 

retirement. 

• Contractor and subcontractor selection should be based on qualifications and not cost 

• joint ventures or subcontracting options, rather than end-to-end outsourcing, for terrestrial 

and hydrographic surveying missions, and 

• close monitoring and evaluation by GCMRC over the contracted work, and strict 

adherence by the subcontractor(s) to QA/QC procedures and delivery schedule. 
 

 

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PART I
 

 

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1. Are control networks, conventional survey, and remotely sensed data collection 

protocols adequate for integrating land based survey data with remotely sensed? 

ANSWER: 

The Panel finds current control networks and surveying methods adopted by GCMRC to be 

adequate to support further ground surveys. For instance, conventional (total station) 

surveying methods are adequate for collecting data on shorelines, for archeological, 

environmental, and topographic surveys. Current control networks, documentation, and 

collection protocols are found to be consistent with similar endeavors of integrating landbased survey data with remote sensing imagery, such as in mapping and geographic 

information system (GIS). 

The Panel, nevertheless, advises that these protocols cannot be generalized as adequate at all 

scales, accuracy requirements, and project specifications. Consequently, the Panel 

recommends that GCMRC evaluates, on a case-by-case basis, the number and distribution of 

ground controls specific to any aerial acquisition. This aspect is independent of the remote 

sensing collection method, whether it is photographic (film-based) or direct digital 

acquisition. 

Panel’s recommendation for network improvements include: Test and evaluation of local 

Continuously Operating Reference Station (CORS) network (South Rim, Hoover and Glen 

Canyon Dams), and application of precise GPS orbits to data processing programs. 
 

 

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2. A. Are site locations for control and other survey sites appropriate? 

B. Are they being appropriately monumented? 

ANSWER: 

A. Are site locations for control and other survey sites appropriate? 

The Panel found that control points were located in a way that makes vertical 

measurements rather difficult. The kind of environment at the Grand Canyon poses 

several limitations, such as lack of access, sky visibility, and points’ inter-visibility. In 

critical areas, such as beaches, the Panel recommends that a minimum of three control 

points be installed. Each of the three points must be inter-visible with the other two. The 

groups (of three points) themselves, however, do not have to be inter-visible with each 

other’s but linked using GPS. 

B. Are they being appropriately monumented? 

The Panel found that control points were not properly monumented. The current '+' 

method impedes efficiency because of their difficulty to locate. Panel’s recommendation 

is that improved, highly stable, easily identifiable and recoverable monumentation to be 

established. This could include the design of a primary and secondary monument types 

(e.g., brass disks, bolts). The design should result in minimal impact yet permanence. 

FURTHER RECOMMENDATIONS: 

The Panel suggests coordinating with the NPS for permission to place new monuments and 

preserve existing control points. These can be strategically placed out of the general park 

visitors view. The Panel further advises GCMRC to coordinate between NPS representatives 

and the Federal Geodetic Control Subcommittee (FGCS). 
 

 

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3. Are the data standards relating to spatial data appropriate (section F)? 

ANSWER: 

The Panel endorses GCMRC’s conformity with national data standards such as the National 

Spatial Data Infrastructure (NSDI), the National Biological Information Infrastructure (NBII), 

and the metadata protocols developed by the Federal Geographic Data Committee (FGDC). 

The Panel however finds that adherence to these standards is not consistent. The three 

examples of metadata delivery, s5geolgeom, fl0001exp0001, and fl0002exp0001, were 

marred with missing information. Most critical of these are accuracy standards. In the 

Panel’s opinion, this represents a serious flaw that, in extreme cases, may render the 

delivered data useless. The Panel questions the acceptance and certification by GCMRC of 

such deliveries from commercial contractors. 

The Panel recommends strict adherence to the standards declared in the protocols. The Panel 

further recommends that GCMRC conform to geospatial positioning accuracy standards, in 

terms of reporting methodology, control networks, and specifications. The FGDC has 

established the Geospatial Positioning Accuracy Standard. The standard is described in the 

following documents: 

Geospatial Positioning Accuracy Standard: 

Part 1, Reporting Methodology, FGDC-STD-007.1-1998 

Part 2, Geodetic Control Networks, FGDC-STD-007.2-1998 

Part 3, National Standard for Spatial Data Accuracy, FGDC-STD-007.3-1998 

FURTHER RECOMMENDATIONS: 

The Panel recommends that accuracy of surface data from active sensors, such as Light 

Detection and Ranging (LIDAR), be evaluated using standards developed by USGS-National 

Digital Elevation Program and the Federal Emergency Management Agency (FEMA)-Flood 

Hazard Mapping Programs. Guidelines are being established for a QA/QC procedures and 

evaluation of data sets in variable vegetation conditions. References may be found at: 

http://www.ndep.gov/TechSubComm.html

http://www.fema.gov/mit/tsd/lidar_4b.shtm

http://www.ncfloodmaps.com/pubdocs/default.htm
 

 

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4. A. Is the current remote sensing statement of work sufficiently defined relative to 

spatial positioning of remotely sensed data? 

B. Please include a review of GPS position dilution of precision (PDOP), minimum 

epoch update rate and synchronization, and simultaneous processing or averaging 

of multiple base-line vectors. 

ANSWER: 

A. Is the current remote sensing statement of work sufficiently defined relative to spatial 

positioning of remotely sensed data? 

The protocol spells out the objectives and applications that justify the collection of 

remote sensing data as well as highly detailed and specific information about flying 

heights, GPS control, and deliverables. The Panel, however, finds that critical 

specifications of aerial and remote sensing data were severely missing. These 

acquisitions need detailed specifications, defined based on the requirements of the 

intended application. For instance, the ground sampling distance, positional accuracy, 

and spectral channels and bandwidth must all be defined according to the goals of the 

application. This is particularly important since it impacts, very substantially, the cost of: 

acquisition, processing, and dissemination. The Panel recommends that numerical, 

quantifiable, and other descriptive specifications be defined in conjunction with the 

intended application; and that such definitions be incorporated into all future RFP’s. 

Advanced technologies and concepts are being constantly introduced in nearly every 

aspect of remote sensing, such as airborne GPS, inertial measurement units, direct 

georeferencing, automatic surface generation, and active sensors. The Panel thus 

emphasizes that the most effective technology and methodology for obtaining services 

and products should be defined based on the nature and specifications of the deliverables. 

This process would allow for industry service providers to respond to solicitations 

utilizing the latest technologies and expertise available. The selection of the best vendor 

to meet GCMRC’s program requirements is therefore expected to utilize a QBS process. 

B. Please include a review of GPS PDOP, minimum epoch update rate and 

synchronization, and simultaneous processing or averaging of multiple base-line 

vectors. 

The protocol stipulates PDOP values not to exceed 3.5 on the aircraft and 5 on the base 

station. The Panel finds these to be generally adequate. The Panel advises that under no 

conditions the PDOP values should exceed 6. The Panel also finds the epoch update rate 

and synchronization of 1 sec to be adequate in general for ground survey applications. 

The Panel recommends that for reliable results in the Grand Canyon, GPS surveying 

activities should be conducted within 30 km from the established base station, with an 

absolute maximum of 50 km. For projects having a potential for GPS failure, multiple 

base stations are recommended for airborne or ground surveys. 
 

 

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5. A. Because geoids are modified periodically and positional data are acquired for 

many GCMRC program requirements on an annual basis, what is the most 

appropriate format (level of processing) for permanent storage of collected data that 

are used for historical or temporal analyses? 

B. Should all the coordinate values be archived, maintained, adjusted, and 

published as Cartesian and/or World Geodetic System 1984 (WGS 84) values to 

bypass geoid model problems? 

ANSWER: 

A. Because geoids are modified periodically and positional data are acquired for many 

GCMRC program requirements on an annual basis, what is the most appropriate 

format (level of processing) for permanent storage of collected data that are used for 

historical or temporal analyses? 

The Panel recommends permanent storage in lat/long as well as Cartesian, such as the 

Earth-Centered Earth-Fixed (ECEF) State Plane, and the Universal Transverse Mercator 

(UTM) coordinate system, i.e., three systems in total. GCMRC staff received another 

advice1, as shown in Appendix III, to limit the use to Cartesian, and to specifically avoid 

latitude and longitude system. The Panel interprets this advice in relation to the use of 

coordinates, rather than storage and archiving. If this interpretation holds true, then the 

Panel concurs with this advice. 

The Panel’s recommendation that the original source of all raw measurements be 

archived primarily in Lat/Long aims to maintain a backup data in case if an error is found 

in the projection parameters or if another projection is used in the future. Furthermore, 

the source data for GPS observations are in geographic coordinates (latitude/longitude). 

Archive of geographic coordinates is required under the National Oceanic and 

Atmospheric Administration (NOAA) charting surveys (ref. 

http://chartmaker.ncd.noaa.gov/hsd/specs/specs.htm Section 8.5.3). 

B. Should all the coordinate values be archived, maintained, adjusted, and published as 

Cartesian and/or WGS 84 values to bypass geoid model problems? 

The Panel recommends that all data be adjusted and processed in the latest solution of 

NAD 83. Except where there are specific needs for orthometric heights, all elevations 

should be determined in NAD 83 ellipsoidal heights. 

Archiving issues were addressed in Section I.5.A above. Publishing issues are subjective 

and depend on the data user. However, once the coordinate system and reference surface 

are defined (hence the meta data requirement), transforming from one coordinate system 

to another can be performed with publicly or commercially available conversion tools. 

 

1

 In terms of Cartesian coordinate systems, this recommendation concurs with that by Mr. Philip A. Davis, Jr. of 

the Astrogeology Group of USGS (520-556-7133) based on recommendation by Mr. Mike Pace of the Midcontinent Mapping Center of USGS (573-308-3771). This is documented in an email communication (no date 

provided) with Mr. Steve Mietz of GCMRC as shown in Appendix III. 
 

 

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FURTHER RECOMMENDATIONS: 

1. The Panel endorses strict adherence to systematic documentation of meta data as described 

in the protocols, namely using Content Standard for Digital Geospatial Metadata Version 

2 - June 1998 published by the FGDC. 

2. The Panel recommends accessing advice from a government agency or commercial 

consulting services if further evaluation of this question is needed. 
 

 

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6. Geoids are established using available gravity data for a region. The Grand Canyon 

is a narrow; deep void that has dramatic changes in bedrock densities along its 

corridor, both of which effect local gravity. 

A. What effect does (can) each of these two factors have on surveys within the 

Grand Canyon that currently use control established from canyon-rim base 

stations?

B. What are the potential magnitudes of these effects on positional accuracy?

C. Can they exceed the target positional accuracy for GCMRC?

D. If, so, how can better control be established?

ANSWER: 

A. What effect does (can) each of these two factors have on surveys within the Grand 

Canyon that currently use control established from canyon-rim base stations? 

A geoid is modeled based on the assumption that the potential of gravitational force is the 

same on the same surface, hence equipotential surface. In a specific region, like the 

Grand Canyon, the Earth's mass may be irregularly distributed throughout the core, 

mantle and crust. These differences in mass concentrations can be treated as mass 

anomalies, which result in variations in the gravitational forces in that region. These 

changes in the gravitational forces affect the flatness of the geoid surface, upon which 

line-of-sight leveling measurements are based. 

To model the effect of these changes, a standard geoid model is first established. Then, 

the deviations of gravity resulting from Earth's true mass distribution are treated as 

anomalies. At regions where mass is concentrated, anomalies are treated positive thus 

causing higher local potentials of gravitation. On the other hand, places where there is 

mass deficiency, local gravitational potentials are lower, hence negative anomalies. 

Consequently, the equipotential surface where the leveling measurement is conducted 

will undulate with changing deflections of the vertical, as shown in Figure 1. This, in 

turn, will affect the ellipsoidal heights of the observed points. The magnitude of such an 

effect, however, is very much dependent on the deflection angle, which is a function of 

the anomalies. 

B. What are the potential magnitudes of these effects on positional accuracy? 

It is in the Panel’s opinion that these effects are negligible in terms of GCMRC’s line-ofsight leveling survey work. It is worth noting however that current national geoid model 

(GEOID99) is not sufficiently refined to model gravity anomalies in the Canyon to the 

required accuracy. As a result, the magnitudes of these effects on positional accuracy 

cannot be accurately estimated absent of experimental evaluation of a best-fit 

equipotential surface. 
 

 

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C. Can they exceed the target positional accuracy for GCMRC? 

They are unlikely to affect the positional accuracy. Notwithstanding, the Panel 

recommends controlled tests to quantify the anomalies of the geoid model in the area so 

that the effects on accuracy can be numerically analyzed. 

Figure 1. Effect of Mass Anomalies on the Geoid. (Source: Geodesy for the 

Layman, the Defense Mapping Agency) 

D. If, so, how can better control be established? 

This will be needed only if controlled tests are conducted and found sufficient 

degradation in accuracy to warrant new controls. The design of the network will 

then depend primarily on the results from the controlled tests. 

DIFLECTION OF THE VERTICAL

NORMAL TO ELLIPSOID

NORMAL TO GEOID

GEOID 

UNDULATION

GRAVITY ANOMALIES 

POSITIVE

GRAVITY ANOMALIES 

NEGATIVE

ELLIPSOID

GEOID

MASS DEFICIENCY MASS SURPLUS
 

 

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7. A. Do we need to improve the geoid locally? 

B. If so, how? 

ANSWER: 

A. Do we need to improve the geoid locally 

The Panel found that the local geoid require improvement. The impact of the current 

geoid on accuracy may not constitute an immediate concern, however, especially 

considering the cost-benefit aspects. The document Geoid Modeling at NOAA by Dru A. 

Smith offers a good example of the financial impacts of a geoid model, NOAA resources 

and partnerships, and future directions. Another document (Milbert, Undated) from NGS 

provides a good example of accuracy assessment of the geoid model in limited 

geographic area. 

B. If so, how? 

The Panel recommends cooperative effort between GCMRC, the NGS and the USGS. 

The geoid can be improved by including observation of absolute gravity sites as well as 

relative gravity measurements using a marine gravimeter and GPS. These observations 

should be conducted on existing NAVD 88 benchmarks published by NGS as part of the 

NSRS. For a detailed step-by-step methodology of geoid modeling and the needed data, 

please refer to Gravity and the Geoid at NGS, by D. Smith. This document also includes 

a brief look at GEOID99 and a discussion of GPS-derived orthometric heights. 

FURTHER RECOMMENDATIONS: 

As an interim solution, the Panel recommends continuing the long-term static GPS control 

surveys GCMRC currently conducting. The current geoid may have insignificant impact on 

critical areas as the relative difference in elevations does. If that is the case, the observations 

of relative differences in ellipsoid heights should be sufficient between areas. The Panel, 

however, recommends that the impact of varying geoid undulations be assessed, quantified, 

and evaluated in terms of the short- and long-term economics. 

REFERENCES: 

Milbert, Dennis G., An Accuracy Assessment of the GEOID96 Geoid Height Model for the 

State of Ohio, National Geodetic Survey, NOAA, Undated. 

http://www.ngs.noaa.gov/PUBS_LIB/oh-rep.html

Smith, Dru A., Geoid Modeling at NOAA, National Geodetic Survey, National Ocean 

Service, NOAA, November 13, 2000 

http://www.ngs.noaa.gov/GEOID/PRESENTATIONS/2000_11_ScottGudes_SilverSpring_G

eoid_at_NGS/index.htm

Smith, Dru A., Gravity and the Geoid at NGS, National Geodetic Survey, Presented at the 

2000, Geodetic Advisor Convocation, Silver Spring, MD, April 11, 2000

http://www.ngs.noaa.gov/GEOID/PRESENTATIONS/2000_04_Convocation_Silver_Spring

_Gravity_and_Geoid/index.htm
 

 

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8. A. What are the issues surrounding conversion between the National Geodetic 

Vertical Datum of 1929 (NGVD 29) and NAVD 88? 

B. Which vertical datum do you recommend using?

ANSWER: 

A. What are the issues surrounding conversion between the NGVD 29 and NAVD 88? 

An important feature of the NAVD 88 program was the re-leveling of much of the firstorder NGS vertical control network. The dynamic nature of the network requires a 

framework of newly observed height differences to obtain realistic, contemporary height 

values from the adjustment. Consequently, NGS identified 50,600 miles for leveling. 

Replacement of disturbed and destroyed monuments preceded the actual measurements. 

This effort also included the establishment of stable "deep-rod" benchmarks, which 

would provide reference points for future line-of-sight as well as space-based GPS 

measurements. Field leveling of the 50,600 miles network was accomplished to Federal 

Geodetic Control Committee (FGCC) first-order, class II specifications, using the 

"double-simultaneous" method (Whalen and Balazs 1976). 

The new general final adjustment completed in June 1991. The resulting overall 

differences for the conterminous United States between orthometric heights referred to 

NAVD 88 and to NGVD 29 ranged from -40 cm to +150 cm. Examples of these 

differences are shown in Figure 2. In most "stable" areas, relative height changes 

between adjacent benchmarks appear to be less than 1 cm. In many areas, a single bias 

factor, describing the difference between NGVD 29 and NAVD 88, can be estimated and 

used for most mapping applications. 

Figure 2. Height differences between NAVD 88 and NGVD 29 due to local 

effects in conterminous United States [After Zilkoski et al., 1992]. 

 

43N 

 

33N 

125W 95W 85W 75W 23W 115W 105W 65W 

! 
 

 

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In the GCMRC operation area, however, a datum conversion between NGVD 29 and 

NAVD 88 may not achieve 1-2 cm accuracy. This is due to the lack of sufficient NSRS 

benchmarks in the region to compute high accuracy conversion. 

The Panel recommends conducting an investigation to address this lack of benchmarks. 

The investigation would involve three parts. First part is the inclusion in the NSRS of all 

historic USGS leveling, new benchmarks, and other high-order leveling networks. 

The second is the partitioning of all benchmarks and associated observations into 

manageable blocks, and performing a simultaneous least-squares adjustment of the entire 

data set. The third is conducting error analysis of datum conversion between NGVD 29 

and the adjusted NAVD 88 to determine if it can achieve the target conversion accuracy. 

B. Which vertical datum do you recommend using? 

The Panel recommends using NAVD 88. 

FURTHER RECOMMENDATIONS: 

In the Panel’s opinion, the cost benefit ratio of establishing new benchmark coverage needs 

to be examined. Existing leveling data should be utilized in a first attempt re-adjustment of 

the datum. The GCMRC staff has utilized reciprocal level techniques with some success. 

These could be utilized in conjunction with historic networks and conventional level runs 

along the Tonto Plateau. 

REFERENCES 

Whalen, C. T., and E. I. Balazs. 1976. "Test Results of First-Order Class III Leveling." 

NOAA Technical Report, NOS 68. Rockville, Maryland: National Geodetic Information 

Center, NOAA. 

Zilkoski, David B., John H. Richards, and Gary M. Young, Special Report: Results of the 

General Adjustment of the North American Vertical Datum of 1988, , American Congress on 

Surveying and Mapping, Surveying and Land Information Systems, Vol. 52, No. 3, 1992, 

pp.133-149. http://www.ngs.noaa.gov/PUBS_LIB/NAVD88/navd88report.htm
 

 

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9. What are the issues surrounding ellipsoid to orthometric height conversion? 

ANSWER: 

The ellipsoid height of a point on the Earth's surface is the distance from the reference 

ellipsoid to the point, measured along the line normal to the ellipsoid. GPS-based points, on 

the other hands, are based on geocentric ellipsoid reference surface, hence ellipsoidal heights. 

Orthometric heights, shown in Figure 3 are based on an equipotential reference surface, e.g., 

the geoid. The orthometric height of a point on the Earth's surface is the distance between the 

geoid surface and the equipotential (level) surface passing through point itself, measured 

along the plumb line normal to the geoid. All line-of-sight leveling runs are based on 

equipotential surfaces passing through the points where measurements are conducted. 

Differences in mass concentrations result in gravitational anomalies, which undulates the 

flatness of the geoid and equipotential surfaces. As explained in Section I.6.A., the 

anomalies on the equipotential surfaces affect the ellipsoidal heights of the observed points. 

An accurate geoid model needs to be available to accurately convert orthometric heights to 

ellipsoidal heights. 

Issues concerning the accuracy of the current geoid model and potential effects on elevation 

accuracy have been discussed at Section I.6.C and I.7. 

Figure 3 Relationships between Ellipsoid, Geoid, and Orthometric Heights. 

Orthometric 

Height 

Mean Sea Level 

Ellipsoid 

Geoid

h

h = Elevation 

Equipotential (Level) 

Surfaces 

Geoidal 

Height 
 

 

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10. Due to the extreme nature of the Canyon environment, is it reasonable to contract 

terrestrial and hydrographic surveying firms to perform or assist the GCMRC 

survey department in Colorado River Ecosystem operations? 

ANSWER: 

In general principle, the Panel contends that contracting terrestrial and hydrographic 

surveying can improve the ability of GCMRC to achieve its stated goals. Several factors, 

however, necessitate careful consideration and assessment of the efficacy of this approach. 

These factors include: 

• the unique and difficult nature and conditions in the Grand Canyon 

• the need for specialized and expensive equipment for such surveying missions, and 

• the internal resistance and apprehension due to a track record of failed contracts. 

As a result, contracting of a surveying mission, end-to-end, may face a real potential of 

budget over-run and untimely delivery. Since other tasks depend on the results of these 

surveys, such failure may have ripple effects on overall GCMRC operations. 

The Panel recommends joint ventures or subcontracting options for these surveys. 

Subcontractors and temporary crews, highly skilled in the particular type of survey and 

closely working with the GCMRC staff, would certainly help in realizing the desired goals. 

While the GCMRC surveying staff has the river and terrain experiences unique to the area, a 

subcontractor may bring the required addition of labor and surveying expertise. 

The Panel stresses two critical factors as key to the success of future surveying missions. 

The first is close monitoring and evaluation by the GCMRC staff over the contracted work. 

This can be realized by making a payment contingent upon approval of a completed phase or 

milestone. The second is strict adherence by the subcontractor(s) to QA/QC procedures and 

delivery schedule. The Panel further recommends imposing specific and enforceable 

stipulations to be embedded in any contract. These stipulations may include non-compliance 

and delay penalties, third party validation requirement, and adherence to the latest national 

standards for services and products specified in the contract.
 

 

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11. Is the staffing level and qualifications of the survey department appropriate? 

ANSWER: 

While reliance on skilled volunteers seems to be an innovative and cost effective approach, 

the Panel recommends increasing the number of permanent staff. Specifically, the Panel 

advises adding two full time survey staff to the already existing two staff members. The 

Panel further recommends that the group should be supplemented with a skilled geodesist, 

either as an employee (50% time) or contract such services with a government agency or 

outside consultant. 

FURTHER RECOMMENDATIONS:

1. The Panel recommends that the survey staff be offered training and continuing education 

on regular basis. This is particularly in subjects like geodesy, emerging technologies such 

as LIDAR, advanced imaging systems, etc. 

2. The Panel warns that GCMRC is at risk because of the size of its surveying staff. Very 

few individuals have intimate knowledge of all unique procedures, specifics of surveying 

projects, and other vital information on all aspects of spatial referencing of the area. The 

Panel recommends that such knowledge be systematically documented, archived, and 

disseminated to other related missions within GCMRC. The Panel further recommends 

contingency plans be developed to deal with risks of staff relocation, downsizing, and 

retirement. The Panel recommends that workshops be conducted to educate other 

GCMRC departments about all controls, surveying missions, and spatial standards, and 

emerging technologies. 
 

 

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PART II
 

 

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1. For each of the following five categories: 

A. Ground based terrestrial surveying, 

B. Airborne terrestrial surveying, 

C. Ground based hydrographic surveying, 

D. Airborne hydrographic surveying, and 

E. Surveying from historical stereo photos; 

Please describe the requirements, limitations, relative cost, level of difficulty, 

sources and magnitude of error, operational status, and required quality control 

and quality assurance of all surveying technology/technique combinations that can 

be used to locate points on the Earths surface in two or three dimensions using real 

world coordinates to within 3 m (meters), 1 m, 0.3 m, and less than or equal to 0.1 

m. In addition to a detailed discussion in the report, please summarize your 

findings in the table below. 

ANSWER:

A. Ground based terrestrial surveying: 

The positioning orientation systems for land vehicles are opening many new venues for 

ground based terrestrial surveying. One of the biggest applications is that of mobile 

mapping. Designed for vehicle applications, position orientation systems, such as the 

Applanix POS-LV, provide high dynamic accuracy in position, roll, pitch and true 

heading. These ground based terrestrial surveying systems are ideally suited for use in 

applications where GPS outages can be an issue. Such an advantage makes them ideal for 

GIS data collection where line of sight is problematic for corridor surveys and river 

mapping. 

B. Airborne terrestrial surveying: 

These methods can be used with film-based aerial photography, direct digital airborne 

acquisition, low-cost digital cameras, and high-resolution satellite imagery. These 

acquisition technologies do not merely produce different data sources, but they impact the 

whole processing approach as well as the expected accuracies. 

a. Film-Based Photogrammetric Methods: This approach includes both conventional 

(i.e., hardcopy) as well as post-scanning softcopy production. In this approach, 

industry standards indicate that two- and three-dimensional accuracy of 0.1 meter can 

be achieved, provided that all photogrammetric requirements are met. These include, 

but not limited to, a Camera Calibration Report supplied by the USGS; appropriate 

number and distribution of GCPs; trained photogrammetrists, and QA/QC 

procedures. 

b. Airborne Integrated GPS/Inertial System for Direct Geopositioning: There are two 

different technologies being introduced to the commercial market, (1) airborne analog 

camera integrated with GPS/Inertial Navigation Systems (INS) and (2) airborne 

digital camera integrated with GPS/INS. They are designed for direct geopositioning, 

thereby in the case of the analog camera bypassing aerial triangulation and in the case 
 

 

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of airborne digital cameras the conversion of film into digital image through precise 

scanning. This approach has been tested in production and may offer an option to 

conventional mapping in the very near future. Currently, Z/I Imaging, Intergraph, 

Emerge Direct Digital Imagery, Integraph, and Leica GeoSystems, are a few that offer 

advanced integrated digital/GPS/INS for mapping. The 3 to sub- meter accuracy 

levels are potentially achievable using this technology. For more information on the 

applicability of airborne aerial cameras integrated with GPS/INS see USGS OpenFile Report 02-222, Positional Accuracy of Airborne Integrated GPS/INS for 

Mapping in Glen Canyon, Arizona. 

c. Low-cost Digital Camera: This technology, such as the Kodak MegaPlus 16.8I digital 

camera, is not a viable option for standard photogrammetric work with high accuracy 

expectations with one or less meters. However, it may be a viable option to achieve 

the 3 meters accuracy levels, assuming all standard photogrammetric requirements 

are met. New digital sensor cameras by Z/I, LeicaGeoSystems, and others may offer 

greater potential and should be investigated. 

d. Remote Sensing Methods: 

This application is mainly based on commercial high-resolution satellite imagery. 

The Quickbird satellite provides the highest resolution available at the present time. 

It is 0.6 meter panchromatic, and thus may be a viable option for accuracies better 

(i.e., numerically smaller) than 3 meters. This option needs to be examined in more 

details with a pilot project. If the intended accuracy is found to be achievable, the 

cost effectiveness of high-resolution satellite imagery becomes a compelling factor. 

C. Ground based hydrographic surveying: 

The best current methods (under the restrictions of working in the Canyon) will come 

from using relatively narrow swath, high resolution, high frequency multibeam sonar in 

conjunction with precision navigation and attitude sensors and methodical calibration 

techniques. Refer to NOAA Specifications and Deliverables 

(http://chartmaker.ncd.noaa.gov/hsd/specs/specs.htm Section 5 Depth Sounding) for error 

sources, quality control and quality assurance. 

There is probably no heading and attitude reference that will work in the Canyon that is 

as good as that provide by GPS-aided inertial platform such as the POS/MV-320 from 

Applanix. This approach will not work in most of the Canyon. A careful field trial using 

an IXSEA PHINS ring-laser gyro should be evaluated. 

 

D. Airborne hydrographic surveying: 

LIDAR from aircraft will provide fast, synoptic mapping of the bottom of the river in the 

canyon but the impact of flying a relatively large plane (Twin Otter) low over the river 

may be an issue. 
 

 

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Perhaps more importantly, the spatial resolution of current generation systems is on the 

order of one meter and is perhaps a factor of ten too crude, and the water surface 

roughness and turibity may not allow for quality data acquisition. 

E. Surveying from historical stereo photos: 

It is in the Panel’s opinion that capabilities and resources at GCMRC are not currently 

compatible to make full use of the historical, near-future, and mid-future photographic 

acquisition missions. These deficiencies include current staffing, expertise requirements, 

level of analysis difficulty, sources and magnitude of error, operational status, and quality 

control and quality assurance protocols. 

FURTHER RECOMMENDATIONS: 

• The Panel recommends that resources from other divisions within the USGS Campus, as 

well as outside contractors, be mobilized to execute specific missions. While this 

practice may be a good solution for the time being, the Panel recommends that GCMRC 

expand its in-house photogrammetric quality control and image analysis capabilities2

. 

• GPS and IMU are technologies that have the potential of reducing, rather drastically, the 

GCP requirements for photogrammetric processing. The Panel recommends however 

that additional GCPs are provided in any photogrammetric coverage, and they must be 

sufficient in number, accuracy, and distribution. These points serve two purposes: first, 

for QC/QA, and second as a back up in case of GPS/IMU failures. 

 

2 A photogrammetric process includes all primary tasks starting with scanning, reformatting, 

interior orientation, exterior orientation, surface generation, editing, error assessment, and 

ending with orthophoto production. Image analysis include temporal, spectral, as well as 

sensor fusion capabilities. 
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Table 1: Summary of technology requirements for various accuracies 

Accuracy 

meters 

Technology/ 

Technique 

Requirement

s 

Limitations Relative Cost Level of Difficulty Sources and Magnitude of Error Op. Status 

3 

Photogrammetry, 

Direct Georeferencing 

Aircraft/ 

Geodetic 

quality Camera

Code-phase 

GPS receivers

Clear sky for 

observation. Not all 

points in the Canyon 

are visible from the 

air 

Missiondependent 

Highly 

specialized data 

collection, 

analysis and 

processing 

GCP, Photo quality, 

scanning, and operator V.Good

mo

staf

1 Photogrammetry Aircraft/ Geodetic quality Camera Same as above Mission- dependent As above As above V.Good A1 GPS Code-phase GPS receivers

Parts of the Canyon 

are difficult to 

obtain GPS 

measurements 

Back-pack 

units 

available for 

>$4,000 

Relatively easy 

to train new 

users 

Significant multipath 

error 

V.Good Sta

0.3 GPS 

dual-frequency 

carrier-phase 

GPS 

Parts of the Canyon 

are difficult to 

obtain GPS 

measurements 

Quality GPS 

units for $8-

15k 

Extensive 

training 

required for 

GPS 

Significant multipath 

error 

Good 

0.3 Traverse Total stations 

Intervisibility and 

ability to place 

definable permanent

monuments 

Total stations

for $7-15k 

Extensive data 

processing 

Systematic errors; 

Magnitude: depends 

on specs of 

instruments; 

≤ 1/15000. 

Good

mo

sta

<0.1 GPS 

Dual-frequency

Carrier-phase 

Parts of the Canyon 

are difficult to 

obtain GPS 

measurements 

Quality GPS 

units for $12-

15k 

Extensive 

training for 

GPS data 

processors 

Significant multipath 

error 

Good 

mo

sta
 

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2. For conventional ground based terrestrial surveying please include a review of: 

A. Equipment (sent as part of the previous mailing)

B. General calibration including maintenance and adjustments of instruments 

and tribrachs

C. Multiple angle and distance measurements to derive various levels of 

D. Minimum and maximum distances traversed in combination with strength of 

measured angles

E. Adjustment procedures that should be used with conventional traverse 

measurements

F. Instrument and target height measurements

G. Back-sight checks

H. Atmospheric calibration of electronic distance measuring equipment (EDM) 

I. Scale factor, etc.

ANSWER:

A. Equipment (sent as part of the previous mailing): 

In the Panel’s opinion, equipment is modern and adequate. 

B. General calibration including maintenance and adjustments of instruments and 

tribrachs: 

The Panel recommends that GCMRC adopt calibration procedures for all the 

equipment. The Panel further recommends maintenance, check up, and calibration 

schedules be established and adhered to. A calibrated base line should also be set up 

for calibrating total station and EDM instruments. The Panel recommends 

comprehensive calibration of all surveying instruments at least once a year. In 

addition, the Panel recommends that tribrachs be checked in the field prior to each 

survey mission. 

C. Multiple angle and distance measurements to derive various levels of control: 

In the Panel’s opinion, these procedures are adequate for the intended accuracy 

standards from the surveys. 

D. Minimum and maximum distances traversed in combination with strength of 

measured angles: 

In the Panel’s opinion, these procedures are adequate for the intended accuracy 

standards from the surveys. 

E. Adjustment procedures that should be used with conventional traverse 

measurements: 

Please refer to B above. If an instrument displays large errors, the Panel recommends 

comprehensive calibration by a certified survey instrumentation specialist. 
 

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F. Instrument and target height measurements: 

In the Panel’s opinion, these procedures are adequate for the intended accuracy 

standards from the surveys. 

G. Back-sight checks: 

In the Panel’s opinion, these procedures are adequate for the intended accuracy 

standards from the surveys. 

H. Atmospheric calibration of EDM: 

The Panel recommends that proper calibration procedures be established in 

accordance with the manufacturer’s specifications. 

I. Scale factor, etc.: 

In the Panel’s opinion, these procedures are adequate for the intended accuracy 

standards from the surveys. 

FURTHER RECOMMENDATIONS: 

It is in the Panel’s opinion that, based on information provided, the methods and 

protocols are adequate for the intended accuracy standards of the terrestrial survey. The 

Panel strongly recommends, however, that testing, adjusting, and calibration issues be 

addressed sufficiently. These include calibration procedures, frequency, certification, etc. 
 

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3. For ground based GPS terrestrial surveying please include a review of 

GIS/database integration strategies and whether or not: 

A. International Terrestrial Reference Frame (ITRF) values should be 

considered 

B. We should be maintaining control ellipsoid or geoid values 

C. We should be using tribrachs or fixed pole height set-ups for GPS 

observations 

D. We should use “fast static” or kinematic applications 

E. Whether or not adjusted GPS values be finalized without precise ephemeris 

data 

ANSWER: 

A. ITRF values should be considered: 

The Panel recommends using ITRF for this purpose. 

B. We should be maintaining control ellipsoid or geoid values: 

The Panel recommends using NAVD 83, as well as keeping all measured data 

archived. 

C. We should be using tribrachs or fixed pole height set-ups for GPS observations: 

The Panel recommends using collapsible fixed height poles on the rim and in the 

canyon. 

D. We should use “fast static” or kinematics applications: 

This depends on the specific project and its specifications. The Panel recommends, 

in general, using fast static approach for critical controls. 

E. Whether or not adjusted GPS values be finalized without precise ephemeris data: 

The Panel recommends, strongly, that adjustment of GPS be carried out with 

ephemeris data. 
 

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4. For airborne terrestrial surveying please include a review of: 

A. Maximum PDOP values 

B. Minimum baseline distance 

C. Minimum number of base stations operating simultaneously 

D. Minimum epoch update rate and synchronization 

E. Requirements of simultaneous processing or averaging of multiple base-line 

vectors 

ANSWER: 

A. Maximum PDOP values: 

Please refer to Question 4 Section B in Part I. 

B. Minimum baseline distance: 

Please refer to Question 4 Section B in Part I. 

C. Minimum number of base stations operating simultaneously: 

The minimum number of base stations in a simultaneous operation is an integral part 

of the survey design process. Typically, the 30 km rule applies, but whenever unusual 

terrain or signal blocking may occur, then additional base stations are required. The 

survey design should be laid out using a adequate terrain model and 3D software 

allowing for the analysis of direct base station to sensor to satellite communication. 

In an area like the Grand Canyon with extreme terrain differences and corners/turns, it 

is likely that twice as many base stations would be required compared to traditional 

survey guidelines. 

D. Minimum epoch update rate and synchronization: 

This was previously answer as a 1 second update rate. 

E. Requirements of simultaneous processing or averaging of multiple base-line 

vectors:
 

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5. For ground based hydrographic surveying please include a review of: 

A. Equipment 

B. Software (data collection, editing, and processing), boat positioning methods 

C. Hydro-acoustic frequency 

D. Patch test 

E. Integration of motion sensor 

F. Effect of heave component on lateral motion 

G. Motion compensation relative to eliminating heave component 

H. Yaw correction 

I. Accuracy of fluxgate compass 

J. Accuracy of fiber optics gyro 

K. Scan angle 

L. Automated statistical filtering 

ANSWERS: 

A. Equipment: 

Current GCMRC multi-beam system is a Reson Seabat 8124. This system has a flat 

array, which is prone to refraction at the sonar head and requires real-time 

measurement of the speed of sound at the array. Refraction at the head is not an issue 

with a curved array, such as the 8101, and would eliminate the need for an acoustic 

velocimeter at the head. Side scan sonar (SSS) capability is a valuable option and can 

be used for anomaly detection in editing and aid in substrate delineation. 

The Panel recommends the use of a multibeam system with wider angular swath 

width (150 degrees). Table 2 shows a comparison of the two systems. A Reson 8101 

mounted at a 15° offset would enable mapping from nadir (directly below the sonar 

head) out to horizontal from the sonar head (90 degrees from nadir) to one side of the 

vessel and from nadir through 60 degrees from nadir to the opposite side of the 

vessel. This would allow for better coverage on shoreline runs. Disadvantages of the 

Reson Seabat 8101 are: The sonar head weight (59lbs) and expense. Advantages are: 

Increased swath width, better range resolution and illuminates the need for a 

velocimeter at the head. 

Table 2 Comparison of Reson Seabat models 8124 and 8101 

Multibeam 

System 

Freq

. 

(kH

z) 

Range 

Resolutio

n 

Array Swath 

Width 

SSS

Opt

. 

Bea

m 

Angl

e 

Power 

Requirement

s 

Reson Seabat 

8124 200 5 cm Flat 3.5 x dpth Yes 1.5 200W – 110V 

Reson Seabat 

8101 240 1.25 cm Curved 7.5 x dpth Yes 1.5 62W – 110V 
 

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B. Software (data collection, editing, and processing), boat-positioning methods: 

Hypack MAX is an excellent choice for data acquisition. Better software is available 

for data editing, analysis and presentation (Caris HIPS) but may require some 

modification for this unique application. The current range-azimuth positioning is the 

best solution given the state of technology, but it is costly. GPS/INS technology may, 

in the future, become capable to address the unique problems encountered in the steep 

canyons. Current systems, such as the POS/MV-320 from Applanix, are not suitable 

because of the limited visibility of the GPS constellations from the canyon floor. 

C. Hydro-acoustic frequency: 

Operating frequency in the 200-250 kHz is ideal. It matches the existing (and 

historical) single beam frequency of 210 kHz of the GCMRC Innerspace echo 

sounder. High frequency (>300 kHz) would provide improved range resolution but is 

likely to be too noisy for conditions and would not be consistent with 210 kHz single 

beam system. Lower frequencies (<100 kHz) are likely to degrade range resolution 

and would require a larger transducer to maintain the same angular resolution. Lower 

frequencies have a tendency to penetrate into fine sediments, thus increasing the 

ambiguity of the observations. 

D. Patch test: 

The Panel makes the following recommendations. Improved patch test procedures 

should be established and adhered to. A robust set of patch tests should be run for 

each field program. All lines should be run at slow speeds except for the compliment 

to the latency line. Roll test lines should be run in deep water over a uniform bottom. 

Routine latency tests should include lines run at different speeds (5 knot difference if 

possible), in shallow water, with nadir beams over target of opportunity (TOP), such 

as a 2 meter boulder on a uniform bottom. Pitch test should include running 

reciprocal lines over a TOP or slope in deep water. Use only nadir beams in pitch 

analysis. Include multiple test lines for confidence in computed values. Run patch 

test at beginning and end of deployment and if sonar head grounds or suspected 

change in alignment. Confirm bias values with swath overlap on TOP on regular 

basis. The detailed patch test results should be included in each survey report. 

E. Integration of motion sensor: 

The Panel recommends setting MRU pitch and roll reference to read 0 degrees, prior 

to patch test, with plumb prism/sonar head mounting pole for accurate position 

translation to sonar head. 

F. Effect of lateral motion on heave component: 

In the Panel’s opinion, it is likely that the present attitude sensor (DMS-05) will result 

in heave artifacts under some circumstances. The Panel recommends careful analysis 

of the dynamics of the survey platform (from existing navigation, bathymetry and 

attitude data). The results of such an analysis should indicate whether the current 

senor is adequate. In the event that there are significant motion induced (or other) 

artifacts in the existing data sets, the Panel then recommends development of a 
 

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comprehensive error budget for the survey system (including the sonar, the attitude 

sensor, the heading reference and the navigation.) Such an error budget can then be 

used to evaluate expected results from improved equipment (Hare et al., 1995). The 

Panel recommends that GCMRC staff review some references on error budgets and 

survey practices published by the Hydrographic Society of America, 

http://www.thsoa.org/references.htm.

If the results of the analysis warrant procurement of better sensors, the Panel 

recommends conducting careful evaluation of potential upgrades, including field 

trials and subsequent analysis. This is to clearly identify an appropriate attitude 

reference system. 

G. Motion compensation relative to eliminating heave component: 

Currently the heave component is not applied. In relatively calm waters this will 

result in better vertical resolution provided use of 6 Hz update from range-azimuth 

system. Survey log should note if conditions include wind chop or significant waves 

from rapids. These areas should be examined for heave artifacts during processing 

and potential application of heave relative to 6Hz range-azimuth vertical reference. 

H. Yaw correction: 

The Panel recommends improving the accuracy of current heading sensor. It is 

possible that using a north seeking ring laser gyro, such as the Octans and PHINS 

from iXSEA, could provide an acceptable heading reference. It would also be a 

superior pitch, roll, and heave sensor. Technical data about Octans gyro can be found 

in http://www.ixsea.com/

I. Accuracy of fluxgate compass: 

The fluxgate compass is prone to magnetic field interference from local attraction and 

systems aboard survey vessel and is not accurate enough. Currently available 

mechanical gyrocompasses or GPS/INS are not a viable solution. It is possible that 

the Octans Fiber Optic Gyrocompass (FOG) described above could be an effective 

solution. Until a replacement is available, GCMRC may have to continue to use the 

fluxgate compass. The Panel recommends testing magnetic field interference from 

power sources and instrumentation to locate source of observed problem when boat 

turns. The Panel recommends relocation of sensor and using more frequent yaw tests 

on bottom features with reciprocal lines and 10-20% overlap of outer beams. 

J. Accuracy of fiber optics gyro: 

Accuracy of previously available fiber optic gyrocompasses are substandard for the 

required accuracy due to drift problems because they are rate gyros. Newer, north 

seeking FOGs such as the Octans or PHINS may prove adequate. The Panel 

recommends detailed evaluation of one or more current-generation FOGs. The Panel 

further recommends using frequent yaw and repeatability patch tests on bottom 

features with reciprocal lines and 10-20% overlap of outer beams. 
 

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K. Scan angle: 

The scan angle is a function of depth and reflectance angle. There is no reason why 

GCMRC can not use beams up to 85 or 90 degrees from nadir on shoreline runs with 

short ranges to shore and >40 degree reflectance angle. The Panel recommends that 

GCMRC document acceptable range for integrated system by redundant comparisons. 

The Panel further recommends that both shallow and deep-water cross-line analysis 

be run and documented for angle cutoff used in data processing. In addition, the 

Panel recommends that documentation include histogram of cross-line error analysis. 

It is possible that sound speed profile differences in backwaters and eddies may result 

in significant errors at wider angular swaths. GCMRC operates under the assumption 

that the entire water mass is isovelocity. The Panel recommends unbiased analysis to 

demonstrate whether this assumption is valid. 

L. Automated statistical filtering: 

The Panel cautions that such techniques could eliminate data that is helpful in 

analysis of anomalies and true bottom detection. One potential result is mapping the 

top of aquatic vegetation instead of the targeted bottom. Thus, the Panel recommends 

that such analyses be conducted with extreme caution. The Panel further 

recommends that detailed documentation of all processing methods be included in 

each data report. The Panel points to work by Brian Calder at CCOM/UNH who has 

recently made significant progress on this front. His existing methods, however, 

require substantial redundancy in the survey data, which may result in increased time 

on the water, cost and survey complexity. 

REFERENCES: 

Hare, R., A. Godin, and L. Mayer, Accuracy Estimation of Canadian Swath (Multibeam) and Sweep (Multi-Transducer) Sounding Systems, Canadian Hydrographic 

Service Report Series, 1995. 

Blackinton, J. G., (1991), Bathymetric Resolution, Precision and Accuracy 

Considerations for Swath Bathymetry Mapping Sonar Systems, IEEE Oceans '91, 

Honolulu, Hawaii, IEEE. 

Calder, B. R. and L. A. Mayer, Robust Automatic Multi-beam Bathymetric Processing,

http://www.thsoa.org/pdf/h01/3_4.pdf
 

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6. Based upon the written communication you have received and the oral 

presentation during the technical briefing session, please answer the following 

for each of the first four categories where protocols have already been 

established: 

A. Is the method of error determination appropriate? 

B. Are the survey data collection methods and technologies employed 

appropriate? 

a. Do they meet “accepted survey practices” for required accuracy and 

precision? 

b. Are there new or more appropriate methods and technologies? 

C. Are the data processing methods being utilized appropriate? 

D. Is the data being archived appropriately? 

E. Is the QA/QC appropriate? 

a. Consistency among staff 

b. Internal accuracy checks 

F. Is the documentation and record keeping appropriate? 

a. Field notes 

b. Office records 

ANSWERS: 

A. Is the method of error determination appropriate? 

Ground based terrestrial surveying: The Panel feels that the method of error 

determination is appropriate, and that the GCMRC staff has sufficient training to 

address this task.

Airborne terrestrial surveying: The Panel finds no protocols or procedures that 

appropriately apply to error determination for airborne terrestrial surveying. 

Ground based hydrographic surveying: The Panel finds no protocols or 

procedures that appropriately apply to error determination for ground based 

hydrographic surveying. NOAA has established specifications for contract surveys ( 

see: http://chartmaker.ncd.noaa.gov/hsd/specs/specs.htm Section 5 Depth Sounding). 

Although GCMRC is looking for tighter tolerances, these procedures should be 

followed to evaluate and minimize errors. The Panel recommends proper 

documentation of system comparisons and quality checks to improve confidence level 

by users and external evaluation. Specifically, the Panel recommends that GCMRC 

report the following: the results of patch tests, cross-line analysis, and sounding 

comparison to alternate source (pole sounding or overlap of topographic data); 

documentation of stated error budget, acquisition and processing methods, frequency 

and location of sound velocity casts, and calibration reports for velocity profiler. 

Airborne hydrographic surveying: 

The Panel recommends that a careful evaluation of the current capability of airborne 

LIDAR systems be made. A primary purpose for such evaluation is to assess the 

feasibility of implementing a carefully designed and controlled experiment to 

determine the efficacy of this technique in the Canyon. Among many other things, 
 

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the impact of low altitude flight needs to be evaluated versus the potential quality of 

data. NOAA has had good results with the Tenix LADS Corporation 

(http://www.tenix.com/Main.asp?ID=30) that owns and operates the Laser Airborne 

Depth Sounder (LADS). Although currently not in use by GCMRC, similar 

redundant comparisons recommended for ground based hydrographic surveying 

should be used to develop a level of confidence in the data. 

B. Are the survey data collection methods and technologies employed appropriate? 

a. Do they meet “accepted survey practices” for required accuracy and 

precision? 

Ground based terrestrial surveying: Answered in Section II.2.

Airborne terrestrial surveying: GCMRC contracts aerial photographic 

acquisition to specialized firms. In general, these firms are equipped with 

appropriate acquisition methods and technologies, and GCMRC provides 

adequate SOW to these firms. The Panel strongly recommends however that 

more detailed specifications be provided describing the methods and technologies 

employed in the aerial acquisition; and stipulating penalties in case of 

noncompliance. 

Ground based hydrographic surveying: The Panel finds that ground based 

hydrographic surveying meet accepted survey practices, but methods should be 

improved to obtain stated accuracy specifications. The Panel recommends 

improving documentation of confidence checks. The Panel recommends as a 

reference NOAA’s document titled Specifications and Deliverables for 

Hydrographic Surveys (http://chartmaker.ncd.noaa.gov/hsd/specs/specs.htm). 

Airborne hydrographic surveying: This technique is not yet proven useful in 

the Canyon. The results of the evaluation suggested above may eventually require 

re-evaluation of the method. 

b. Are there new or more appropriate methods and technologies? 

Most of this question has been already answered. Please refer to respective 

sections as appropriate: 

Ground based terrestrial surveying: The Panel endorses GCMRC’s use of total 

station instruments, since it is the best current technology available for ground 

based terrestrial surveying. 

Airborne terrestrial surveying: Answered in Section II.1.B. 

Ground based hydrographic surveying: Answered in Section II.5. In addition, 

there have been advances in heading sensors which would improve overall system 

accuracy.

Airborne hydrographic surveying: The Panel finds that current technology 

may not meet GCMRC accuracy requirements. 
 

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C. Are the data processing methods being utilized appropriate? 

Ground based terrestrial surveying: Answered in Section II.2.

Airborne terrestrial surveying: The Panel found that GCMRC did not have inhouse capabilities to process aerial and remote sensing imagery using standard 

photogrammetric procedures. 

Ground based hydrographic surveying: Answered in Section II.5. No review or 

documentation of data processing methods was provided. The Panel recommends 

that GCMRC implements procedures described earlier to document survey and data 

processing methods. In addition, Hypack continues to improve on data processing 

abilities and is adequate. 

Airborne hydrographic surveying: GCMRC does not conduct hydrographic 

surveying using airborne platforms. Unless a need arises in the future, the Panel does 

not recommend this approach at the present. 

D. Is the data being archived appropriately? 

Ground based terrestrial surveying: Based on the description provided for review, 

the Panel finds current archiving procedures to be appropriate for ground based 

terrestrial surveying. It is important that some type of back up system exists such as 

tape.

Airborne terrestrial surveying: The Panel found that current online and offline 

archiving capabilities support only fraction of aerial and other remote sensing 

imagery. These needs will become more critical if historical photography is to be 

converted into digital files. Additional storage and archiving capabilities with robust 

software will be needed for derivative and processed imagery. 

The Panel recommends evaluation of storage, archiving, and networking needs based 

on post-conversion softcopy processing of historical photography. 

Ground based hydrographic surveying: The Panel found no archiving protocols or 

resources specific to ground based hydrographic surveying. 

The Panel recommends that all raw data files be archived along with files generated at 

all stages of the processing pipeline. 

Airborne hydrographic surveying: The Panel found no archiving protocols or 

resources specific to airborne hydrographic surveying. 
 

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E. Is the QA/QC appropriate? 

This question has been partially answered in Section II.1. In addition, there was no 

specific documentation of QA/QC procedures to review during the protocol 

evaluation. The Panel therefore recommends establishing appropriate QA/QC 

procedures for each of the four measurements categories. The Panel further 

recommends that contractors and subcontractors submit their QA/QC procedures 

specifically used to realize the contracted specifications. 

a. Consistency among staff: 

The Panel found no established procedures to ensure consistency among staff. 

Such consistency becomes critical especially when SOW, specifications, data, and 

procedures are communicated among various organizational units of GCMRC. 

b. Internal accuracy checks: 

The Panel found no established procedures to verify adherence to accuracy 

specification. This applies to internal operations as well as contracted work. 

Section I.10 addresses QA/QC adherence requirement and enforcement 

recommendations. The Panel recommends establishing internal verification and 

validation protocols, including methodology, equations, checkpoints, and 

certification. The Panel recommends that GCMRC staff, or an independent third 

party, verify adherence to these protocols in internal as well as contracted work. 

F. Is the documentation and record keeping appropriate? 

a. Field notes 

b. Office records 

The Panel stated specific findings and made recommendations throughout this 

document. These include Section I.3 on data standards and delivery; Section I.5 

on coordinates; Section II.6.A on error determination; and Section II.5 on 

hydrographic measurements. 

.
 

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7. Please provide recommendations to correct observed deficiencies: 

ANSWER:

Recommendations previously noted following each question. 
 

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Appendix I 

Panelists’ Contact Information 

Dale Chayes 

Lamont-Doherty Earth Observatory of 

Columbia University 

Phone: (845) 365-8434 

Fax: (845) 359-6940 

E-mail: dale@ldeo.columbia.edu

Jon L. Dasler, PE, PLS 

David Evans and Associates, Inc. 

2100 SW River Parkway 

Portland, Oregon 97201 

Phone: (503) 223-6663 

Fax: (503) 223-2701 

E-mail: jld@deainc.com

David R. Doyle 

NOS HQTR Route: N/NGS2 

SSMC4, 13th floor 

1305 East West Highway 

Silver Spring, Maryland 20910 

Phone: (301) 713-3178 x105 

Fax: (301) 713-4324 

E-mail: Dave.Doyle@noaa.gov

Richard D' Sanchez 

U.S. Geological Survey 

USGS mailstop: 521 

12201 Sunrise Valley Drive 

Reston VA 20192 

Phone: (703) 648-5121 

E-mail: rsanchez@usgs.gov

Mike Renslow 

Spencer B. Gross, Inc. 

13545 NW Science Park Drive 

Portland, OR 97229 

Phone: (503) 646-1733 

Fax: (503) 626-4818 

Cell: (503) 970-9937 

E-mail: mike@sbgmaps.com

E-mail: renslow@efn.org

John J. Rose, R.L.S. 

Maricopa County DOT 

2901 West Durango Street 

Phoenix, Arizona 85009 

Phone: (602) 506-4679 

Fax: (602) 506-3939 

E-mail: johnrose@mail.maricopa.gov

Raad A. Saleh, Ph.D. 

S&J International 

3 Bluebird Ct. 

Madison, WI 53711 

Phone: (608) 238-4825 

Fax: (661) 420-5127 

E-mail: rsaleh@charter.net
 

 

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Appendix II 

Survey Protocol Evaluation Panel Questions 

Part I: General Questions:

1. Are control networks, conventional survey, and remotely sensed data collection protocols 

adequate for integrating land based survey data with remotely sensed? 

2. Are site locations for control and other survey sites appropriate? Are they being 

appropriately monumented? 

3. Are the data standards relating to spatial data appropriate (section F)? 

4. Is the current remote sensing statement of work sufficiently defined relative to spatial 

positioning of remotely sensed data? Please include a review of PDOP, minimum epoch 

update rate and synchronization, and simultaneous processing or averaging of multiple 

base-line vectors. 

5. Because geoids are modified periodically and positional data are acquired for many 

GCMRC program requirements on an annual basis, what is the most appropriate format 

(level of processing) for permanent storage of collected data that are used for historical or 

temporal analyses? Should all the coordinate values be archived, maintained, adjusted, 

and published as Cartesian and/or WGS 84 values as to bypass geoid model problems? 

6. Geoids are established using available gravity data for a region. The Grand Canyon is a 

narrow, deep void that has dramatic changes in bedrock densities along its corridor, both 

of which effect local gravity. What effect does (can) each of these two factors have on 

surveys within the Grand Canyon that currently use control established from canyon-rim 

base stations? What are the potential magnitudes of these effects on positional accuracy 

and can they exceed the target positional accuracy for GCMRC? If, so, how can better 

control be established? 

7. Do we need to improve the geoid locally? If so, how? 

8. What are the issues surrounding conversion between NAVD29 and 88? Which vertical 

datum do you recommend using? 

9. What are the issues surrounding ellipsoid to orthometric height conversation? 

10. Due to the extreme nature of the Canyon environment, is it reasonable to contract 

terrestrial and hydrographic surveying firms to perform or assist the GCMRC survey 

department in Colorado River Ecosystem operations? 

11. Is the staffing level and qualifications of the survey department appropriate? 
 

 

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Part II: For each of these five categories:

A. Ground based terrestrial surveying 

B. Airborne terrestrial surveying 

C. Ground based hydrographic surveying 

D. Airborne hydrographic surveying 

E. Surveying from historical stereo photos 

1. Please describe the requirements, limitations, relative cost, level of difficulty, sources and 

magnitude of error, operational status, and required quality control and quality assurance 

of all surveying technology/technique combinations that can be used to locate points on 

the Earths surface in two or three dimensions using real world coordinates to within 3 m 

(meters), 1 m, 0.3 m, and less than or equal to 0.1 m. In addition to a detailed discussion 

in the report, please summarize your findings in a table of which an example is provided 

below.

Accuracy in 

meters 

Technology/ 

Technique 

Requirements Limitations Relative 

cost 

Level of 

difficulty 

Sources 

and 

magnitude 

of error 

Operational 

status 

Required 

quality 

control and 

quality 

assurance 

3 

1 

0.3 

<0.1 

2. For conventional ground based terrestrial surveying please include a review of: 

• equipment (sent as part of the previous mailing) 

• general calibration including maintenance and adjustments of instruments and 

tribrachs 

• multiple angle and distance measurements to derive various levels of control 

• minimum and maximum distances traversed in combination with strength of 

measured angles 

• c adjustment procedures that should be used with conventional traverse measurements 

• instrument and target height measurements 

• back-sight checks 

• atmospheric calibration (edm ppm) 

• scale factor, etc. 

3. For ground based GPS terrestrial surveying please include a review of GIS/database 

integration strategies and whether or not: 

• ITRF values should be considered 

• we should be maintaining control ellipsoid or geoid values 

• we should be using tribrachs or fixed pole height set-ups for GPS observations 

• we should use “fast static” or kinematic applications 

• whether or not adjusted GPS values be finalized without precise ephemeris data 
 

 

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4. For airborne terrestrial surveying please include a review of: 

• maximum PDOP values 

• minimum baseline distance 

• minimum number of basestations operating simultaneously 

• minimum epoch update rate and synchronization 

• requirements of simultaneous processing or averaging of multiple base-line vectors 

5. For ground based hydrographic surveying please include a review of: 

• equipment 

• software (data collection, editing, and processing), boat positioning methods 

• hydro-acoustic frequency 

• patch test 

• integration of motion sensor 

• effect of heave component on lateral motion 

• motion compensation relative to eliminating heave component 

• yaw correction 

• accuracy of fluxgate compass 

• accuracy of fiber optics gyro 

• scan angle 

• automated statistical filtering 

6. In addition, based upon written communication you have received and oral presentation 

during the technical briefing session, please answer the following for each of the first four 

categories where protocols have already been established: 

A. Is the method of error determination appropriate? 

B. Are the survey data collection methods and technologies employed appropriate? 

a. Do they meet “accepted survey practices” for required accuracy and precision? 

b. Are there new or more appropriate methods and technologies? 

C. Are the data processing methods being utilized appropriate? 

D. Is the data being archived appropriately? 

E. Is the QA/QC appropriate? 

a. Consistency among staff 

b. Internal accuracy checks 

F. Is the documentation and record keeping appropriate? 

a. Field notes 

b. Office records 

7. Please provide recommendations to correct observed deficiencies. 
 

 

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Appendix III 

Documentation of advice

Steve, 

I talked with a mapping expert at the Mid-continent mapping 

center (USGS) in Rolla, MO today. His name is Mike Pace 

(573-308-3771 ). He is One hour ahead of AZ. He teaches a 

mapping course on Monday, but will be in the office today and 

the rest of next week. 

One definitive piece of advice he gave was NOT to put the 

data in geographic lat, long because it induces too much distortion. 

The remaining options are UTM and State Plane, each has their 

own drawbacks and advantages. Both projections are 

conformal and designed to retain shape, but not true area. Both 

have errors associated with distance measurements, but the State 

Plane is more accurate giving on 1 part per 10,000 error in distance, 

whereas UTM gives 4 parts error per 10,000 units of distance.,which 

is why state's adopted their own state plane projections to minimize 

the error in distance measures for a particular region. Although UTM 

would produce a single database within a single zone, its error is higher 

and reprojection to the state plane quadrants would require resampling 

of data because UTM and state plane have different orientations. He said 

the disadvantage of state plane is that the study area crosses three 

different SP quadrants and G1S .software (as far as he knows) cannot handle analyses 

on an area with I1multipleprojectios. He said it might be advisable to 

keep the data in two projections: one for the site specific studies that require 

high accuracy measurements(SP)and another that can display all of the 

GCMRC area as a single database (UTM). If SP is the projection for 

storing the original data (to maintain accuracy), can EQ process their 

data into 3 SP quadrants? 

I told Mike Pace that you might call him later today or next week to get 

this information directly. He said that is fine. He will be out all day 

Monday teaching a class. 

Philip A. Davis Jr. 

U.S..Geological Survey 

Astrogeology Group 

2255 North Gemini Drive 

flagstaff, AZ 86001 

(520) 556-7133- voice 

(520) 556-7090 – fax 
 

 

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Appendix IV 

Abbreviations of Terms used in the Report 

CORS Continuously Operating Reference Station 

CRE Colorado River Ecosystem 

ECEF Earth-Centered Earth-Fixed 

EDM electronic distance measuring equipment 

FEMA Federal Emergency Management Agency 

FGCC Federal Geodetic Control Committee 

FGCS Federal Geodetic Control Subcommittee 

FGDC Federal Geographic Data Committee 

FOG Fiber Optic Gyrocompass 

GCMRC Grand Canyon Monitoring Research Center 

GCP Ground Control Point 

GIS Geographic Information System 

GPS Global Positioning System 

INS Inertial Navigation Systems 

IMU Integrated Measurement Unit 

ITRF International Terrestrial Reference Frame 

LIDAR Light Detection and Ranging 

NAD 83 North American Datum of 1983 

NAVD 88 North American Vertical Datum of 1988 

NBII National Biological Information Infrastructure 

NGS National Geodetic Survey 

NGVD 29 National Geodetic Vertical Datum of 1929 

NOAA National Oceanic and Atmospheric Administration 

NPS National Park Service 

NSDI National Spatial Data Infrastructure 

NSRS National Spatial Reference System 

PDOP position dilution of precision 

PEP Protocol Evaluation Program 

QA/QC Quality Assurance / Quality Control 

SOW scope of work 

SSS Side scan sonar 

TOP target of opportunity 

USGS U.S. Geological Survey 

UTM Universal Transverse Mercator 

WGS 84 World Geodetic System 1984