# Presentation: 671123

## Using Commercial Satellite Imagery 

**Using Commercial Satellite Imagery **
**and GIS to Update NOAA ENCs**

**Mike Espey**
**Remote Sensing Division,**
**National Geodetic Survey**

**NGS Convocation,**
**Silver Spring, Maryland, **
**October 24-28, 2005**

## Digital Chart Data: ENC vs. Raster Charts

- Image credit: OceanGrafix

- Image credit: Morintech Navigation AS (**dKart Explorer**)

## The “ENC Validation Initiative”

**Notes:**
In response to the known deficiencies of the NOAA ENCs, the ENC Validation Initiative is underway
What is the ENC Validation Initiative?
Incorporation of high resolution commercial satellite imagery and GIS methodologies into the chart production process in order to rapidly assess and correct the problems in NOAA ENCs inherited from the paper charts

ENC data superimposed over high res sat image in ArcGIS
Example of scaling/positioning problem inherited from paper chart (note fit of vectors on left side vs. right)

## Overview: A Multi-Organizational Process

**Notes:**
ENC validation is a PROCESS made up of multiple tasks performed by several different organizations within NOAA.
Since different organizations share responsibility, communication is very important.
To facilitate communication throughout the process, the Chart Evaluation File (or “CEF”) was established to track individual issues or ENC features in question.

The flowchart illustrates the path of the CEF through the ENC validation/update process, can also be a useful roadmap as we talk about the individual tasks making up this process.  (We’ve kept it on the side of most slides, as a reference.)

Specifically what is a CEF? 
Basically a spatially enabled comment file, spatially linking comments and other info to the ENC features in question
A GIS layer in shapefile format (de facto standard for spatial data exchange – widely  used, open format)
Useful as a GIS layer because it can be digitally superimposed over other digital data (ENCs, raster charts, etc.)

## Overview: A Multi-Organizational Process

**Notes:**
The table at right depicts the structure of the attribute table of the CEF
Color codes depict organizational responsibility for populating certain attributes of the CEF as it makes its way through the validation process
About 20 different attributes

Most interestingly, many orgs don’t use ESRI software to populate the attributes they’re responsible for

## Coast and Shoreline Change Analysis Program

**C**oast and **S**horeline **C**hange **A**nalysis **P**rogram

- CSCAP: ENC Change Analysis

-  Internal program within the RSD,  under the Coastal Mapping Program
-  Developed in order to focus limited coastal mapping resources
-  Rapid assessment of chart shoreline using commercial satellite imagery

**Notes:**
ENC validation process begins in Requirements Branch of Remote Sensing Division of NGS with the initial change analysis

Change analysis takes place within the context of CSCAP (coast and shoreline change analysis program)

CSCAP was orig started as a means of rapidly assessing chart shorelines using commercial satellite imagery in order to focus limited production resources
Various types of imagery were experimented with for use in CSCAP; including SPOT, IRS, SPIN-2, IKONOS and Quickbird

## CSCAP: ENC Change Analysis

-  Planning: The Matrix of Life
-  Ordering Imagery (the cheap stuff)
-  High resolution (≤1m)
-  Non-orthorectified
-  Low positional accuracy

**Notes:**
satellite imagery is purchased according to “Matrix of Life” 
A planning document which organizes ENC ports according to 2, 3, and 4 year revisit cycles based on ENC production priorities.

Satellite imagery used for CSCAP is: 
Lowest cost basic product
Very high resolution 
Non-orthorectified (unsuitable for features at higher inland elevations, tall features)
Relatively low positional accuracy (15-25m)

## CSCAP: ENC Change Analysis

-   Change Analysis Using Imagery
-  Quick georeferencing
-  ENC comparison
-  Document discrepancies (CEF)

**Notes:**
Once imagery received, first step is quick georeferencing in ArcGIS, line imagery up with ENC (relative repositioning)
Facilitates direct comparison between

Comparison task begins:
Concentrate on critical port infrastructure, charted features at/above HW (visible at all stages of tide)
Looking for features in ENC not on image (removed, torn down)
Features in image not on ENC (new construction)
Evaluates relative positioning of ENC features, looks for misaligned features 
ENCs/charts a composite of data from multiple sources 

All significant discrepancies are logged in the CEF
Polygon drawn around area in question
Descriptive info added to attribute table (comments)

## CSCAP: Compilation of Changes

- _Refine ABSOLUTE ACCURACY of image_
-  Existing RSD Digital Shoreline?
-  If Not, Obtain Ground Control Points
-  GCP request sent to NRT / other

**Possible scenarios:**
**No compilation needed**
**Limited compilation**
**Extensive compilation**
**Re-compile entire ENC photogrammetrically**

**Notes:**
Once analysis is complete, project passed to Applications Branch of RSD with analyst’s recommendations on how to fix ENC: (one of these four possible scenarios)

If 2 or 3, AB makes preparations to compile from satellite image

Main preparation is to REFINE THE ABSOLUTE ACCURACY of the imagery, so features can be compiled very accurately;  To do this, accurate ground control needed
RSD digital shoreline available for area?
IF NOT, AB turns to NRTs/other field personnel to collect GCPs
 Select locations within the image where control is necessary... [near L/W interface, near compilation areas, stable locations of high contrast in image]
 Create screenshots and other supplementary data to NRTs to help them find these locations on the ground

## CSCAP: Compilation of Changes

**NRT collects GCPs**

## CSCAP: Compilation of Changes

-  Absolute re-georeferencing  (**IMAGINE**)
-  Compile Features from Imagery
-  ArcGIS, shapefiles
-  Use CEF as target areas
-  Double check ENC positioning

**GCP #8**

**GCP #8**

**Possible scenarios:**
**No compilation needed**
**Limited compilation**
**Extensive compilation**
**Re-compile entire ENC photogrammetrically**

**Notes:**
Once GCPs rec’d by AB, used to re-georeference the imagery to higher absolute accuracy (3-5m)
Using Erdas IMAGINE  (more robust, calculation of CE)

Once positioning of satellite imagery refined to higher absolute accuracy:
Features are compiled in ArcGIS in shapefile format
With imagery, CEF, ENC displayed; features tied into ENC using SNAP
CEF is used to target areas /features for compilation
Given the refined absolute accuracy of the imagery, absolute positioning of ENC features double checked (uniform shift)

CEF, shoreline compilation, satellite imagery, other supporting files are passed to MCD of OCS

## ENC / Chart Production Analysis

-  RSD Data Registered as Chart Source
-  Digital Registry (DREG)
-  ENC Production (LAMPS)
-  TRANSLATE
-  CEF MARKUP (optional)
-  MCD Stores CEF
-  MCD / NSD coordination
-  Ready to be deployed in field

**Notes:**
MCD receives data from RSD and registers as chart source, loads into Digital Registry (DREG)

CEF and shoreline compilation is passed to both production groups (ENC and raster)
(optionally) ENC production has ability to add comments to CEF during application of data

MCD stores CEF and supporting files until there is an NRT in the area, then forwards to field

## Field Verification

- They also do GIS!!

**Notes:**
Some of the hardest working folks at NOAA, they even do GIS!
Duties of the NRTs include:
Collecting ground control to support RSD compilation from satellite imagery (upper left)
Positioning navigational aids with GPS (right)
Verifying/disproving existence of submerged hazards (lower left)
Verifying/modifying features RSD collected from imagery 

## Field Verification

-  Preparation for Field Work
-  Filter CEF?  (Blgs, Lmks)
-  File conversions (MapInfo, UTM)
-  Field Work
-  Targeted discrepancies (CEF)
-  Impromptu edits to shoreline data
-  Post-mission Processing
-  Editing the CEF? (**CARTO_REC**)
-  Submitting the CEF to RSD

**Notes:**
Highlight that of two products that require field verification:
CEF = targeted discrepancies
DCFF (compilation, lines and point features) = “if you notice anything wrong as you go” type verification

## Application of Field Verification Data

-  Edits to NGS Shoreline Database
-  Issue Shoreline Update Notice (SUN)
-  Thru NOAA Shoreline Data Explorer
-  Specifies _what_ changes and _where_
-  New source data for ENCs

**Notes:**
CEF / other files return to Applications Branch of RSD

If verification reveals any necessary edits to original shoreline files, these edits are made to master NGS shoreline database

Rather than resubmit a corrected version of the entire original shoreline compilation, RSD issues Shoreline Update Notice (SUN)
Through the NOAA Shoreline Data Explorer website
Distribution system used to distribute shoreline data to MCD
SUN zeroes in on only what was actually changed in the shoreline database 
MCD treats data from the SUN  as new source data, and only has to apply updates to ENC/charts

## Application of Field Verification Data

-  Field-edited CEF to MCD
-  DREG
-  Field data not reflected in SUN	is applied to chart
- Ex. MAINTAIN to REMOVE
-  End result of validation:
- 	***A more accurate ENC/chart!***

**Notes:**
(new as result of Savannah field exercise) MCD also receives field edited CEF

RSD must change name of CEF to reflect field edited status
Example: RSD recommended MAINTAIN could be changed to REMOVE as a result of field investigation (SSS obtained to prove feature is gone)

Raster and ENC production gets CEF, filters on pertinent comments

MCD stores final field-edited CEF 

## Conclusions

-  Implementation Challenges
-  Communication
-  Adoption of new technology
-  Separate organizations
-  Different missions
-  GIS training
-  Future work
-  Demonstration project(s)
-  Coordination meetings

**Notes:**
Given that ENC validation is a new workflow and given the complexity of the workflow, it is expected that there will be challenges to smooth successful implementation and execution

First, communication. 2 Program Offices, 3 Divisions, numerous branches at headquarters plus NRTs running around all over the country.
Adoption of new technology in different organizations. 
FOR EXAMPLE: If NRTs replaced all their laptops with Apple computers that would present a serious problem to the workflow
Last is GIS training. The new workflow is heavily reliant on GIS technology and methodologies. For smooth execution and data transfer people should at least be GIS knowledgeable if not GIS savvy

Future work?

## Questions / comments

- _[Mike.Espey@noaa.gov](mailto:Mike.Espey@noaa.gov)_
**301-713-2685 x153**

**Questions / comments**
**Mike Espey, Team Leader, Coastal Mapping Program**
**Applications Branch, RSD/NGS**