Development of Digital Elevation Model for Antigua, Barbuda, St. Kitts, and Nevis


Project Completion Report

Submitted to

Steven Stichter
Post-George Disaster Mitigation in Antigua/Barbuda and St. Kitts/Nevis
Organization of American States
Tel (202) 458-3300 | Fax (202) 458-3560
Email: sstichter@oas.org 

Submitted by

Jacob Opadeyi
Faculty of Engineering, The University of The West Indies
St. Augustine, Trinidad and Tobago, West Indies
Telephone (868) 662-1134 | Fax: (868) 662-4645
Email: jopadeyi@eng.uwi.tt

October 20, 2000


Development of Digital Elevation Model for Antigua, Barbuda, St. Kitts and Nevis

Executive Summary

This report describes the results of a component of Post-Georges Disaster Mitigation (PGDM) that led to the generation of Digital Elevation Model (DEM) for the following islands: Antigua, Barbuda, St. Kitts and Nevis. The DEM provides an important input parameter toward meeting the objective of PGDM. The DEM can be used to provide a three-dimensional view of the terrain in each of the islands as opposed to the two-dimensional view provided by topographic maps. The 3-D view as a more realistic view of the terrain can also be used to provide information on other terrain parameters such as slope, aspect etc. Using GIS technology the topographic maps of each of the island were manipulated to provide the DEM products.

Background

The goal of the Post-George Disaster Mitigation (PGDM) program is to reduce the vulnerability of population and economic activities in St. Kitts and Nevis and Antigua and Barbuda to natural hazards, including tropical storms and related flooding and seismic and volcanic hazards, through enhanced capacity for hazard mitigation. Under this broad goal, four specific objectives will be pursued in each country:

  1. Develop, adopt and begin implementation of effective national hazard mitigation policies and operational plans.
  2. Adopt national building codes and improve building practices.
  3. Establish comprehensive national emergency shelter policies and programs, with appropriate training for emergency and shelter managers.
  4. Increase public understanding of the need and options for hazard mitigation, through public information and education programs.

One key input parameter needed for the realization of these objectives is a digital terrain model that can be used to generate a three-dimension perspective of the terrain.

Introduction

The following report outlines the outcome of a project designed to develop a digital elevation model (DEM) for the islands of Antigua, Barbuda, St. Kitts and Nevis. The approach used in meeting the requirement relied on the use of existing hardcopy topographic maps, aerial photographs, spots heights and other thematic data. The overall objective for this assignment is to provide OAS with a usable DEM and related products that meets the accuracy expected from the input data.

Methodology

The general methodological steps used are as follows: Requirement Analysis and Collection of Data; Database Design; Data Automation and Error Trapping; Generation of Digital Elevation Model; Development of Digital Orthophoto; and Verification of results

Step 1. Requirement Analysis and Collection of Data

The project began with a requirement analysis meeting. The meeting was with held with OAS project manager and other key local personnel in each of the countries. The objectives of the planning meeting were:

  1. Gaining an understanding of the PGDM program.
  2. Discussion of major issues and challenges.
  3. Reviewing of existing programs and procedures.
  4. Identification of any relevant contacts for the project.
  5. Collection of relevant input data.

Below is the list of persons contacted:

Code

Persons

   

Antigua

Alva Guishard, DCA

1-268-462-6427

authority@candw.ag

 

Rosemary Georges, Project Coord.

1-268-460-9329

moja-nia@usa.net

 

Philmore James, Fisheries Dept.

1-268-462-6106/1362

abiola@hotmail.com

 

Calvin Greenaway, Chief Surveyor

1-268-462-3800

 

St. Kitts

Patrick Williams, Phy. Planning

1-869-465-2277/4702

 
 

Graeme Brown, Phy. Planning

1-869-465-2521 x1058

mastergraeme@hotmail.com

 

David Keith, Project Coord.

1-869-465-5634

 
 

Ken Parker, OAS Office

1-869-465-2636

 
 

Dwight Francis, Survey Dept.

1-869-662-2727

Surveyor1@hotmail.com

Nevis

Lewis Newton, Planning Dept

1-869-469-5521 ext 2040

 

Step 2. Database Design

Upon completion of the requirement analysis and the data collection exercise, the logical database design was undertaken. The ESRI ArcView GISTM 3D Analyst, and Spatial Analyst software were selected as the development tool. Hence the data automation processes were designed to match the data format requirements of these software.

Step 3. Data Automation and Error Trapping

Data automation was undertaken using on-screen digitizing of scanned and georeferenced topographic maps. A mix of automatic vectorization using R2VTM software and manual vectorization using ArcView GISTM was used. The quality of the vectors was verified by overlaying the vectors on the georeferenced digital maps. Appropriate corrections were applied to ensure that the digital vectors of the contours are same as the hardcopy contours.

Step 4. Development of Digital Elevation Model

The DEM was developed from the vectorized contours by first using ArcView 3D AnalystTM to produce the Triangular Irregular Network (TIN). In order to improve the quality of the DEM, features like roads, rivers, lakes, spot heights, buildings were included in the generation of the TIN. The TIN themes were then converted to elevation grids in ASCII format. The resulting elevation raster grids were subsequently converted to XYZ ASCII text files. The text files were subsequently converted to ESRI 3D shapefiles.

Step 5. Development of Digital Orthophoto

In addition to the vectorization of the contours, the aerial photographs of some locations were scanned and georectified towards the production of digital orthophoto of these locations. The PCI OrthoEngineTM software was used for this purpose. The digital orthophoto greatly enhance the visualization of the features on the terrain.

Step 6. Verification of results

Quality control and quality assurance were built into the project through pre- and post-processing checks. The necessary checks were undertaken using the input maps and spot height data. The scanned georeferenced maps were used for quality assurance. The accuracy of the output was verified using two methods. The first method involve the over plotting of the digitized contour lines on top of the scanned and georeferenced topographic maps. This provides visual evaluation of the accuracy of digitizing. The main concerns here are errors due to possible map media distortion. The second method involved the comparison of the interpolated values with the spot height values. The results obtained are very accurate.

Products Generated

The project was completed within the 15 days promised from the inception date. The following products were delivered to OAS at the end of the project:

  1. DEM in ASCII text format and 3D Shapelife format
  2. Digital orthophoto in TIFF format
  3. Georeferenced digital map in TIFF format
  4. Digital contour lines in Shapelife format
  5. Scanned aerial photographs in TIFF format

The appendix contains the data dictionary of the delivered products. It is hoped that the products meet your requirements, if you have any questions or comments, please do not hesitate to call or email me at any time.

Conclusion

This project component has led to the production of a unique product for the two countries: the digital terrain model that can be used by a wide variety of professionals for variety of purposes. The products generated however, suffers from the following drawbacks:

  1. Lack of current topographic maps of the countries
  2. Lack of large scale topographic maps of the countries except for Barbuda where a 1/10,000 map was used
  3. Insufficient spot heights especially for Antigua.

Efforts should be made at eliminating these drawbacks in future works.


APPENDIX

Data Dictionary for Antigua PGDM DEM Project

FolderName

FileName

Content

Attribute data

Antgrid

 

DEM in Raster grid

Cell size = 39.339m

     

# of rows = 495

     

# of columns = 630

Anttin

 

TIN layer

 

Info

 

System files

 

Shapefiles

Antcoast.shp

Coastlines

 
 

antconto.shp

Contours

Htm (heights)

 

antspot.shp

Spot Heights

heights

 

antroad.shp

Roads

 
 

antdrain.shp

Drainage

 
 

antponds.shp

Ponds

 
 

antmangr.shp

Mangroves

 
 

antcorals.shp

Coral reefs

 
 

antcliff.shp

Cliffs

 
 

ant3dptz.shp

3D shapefile of points

 

Otherfiles

Antigua.apr

Arcview project

 
 

antxyz.txt

XYZ in ASCII text format

 
 

antxyz.dbf

XYZ in DbaseIV format

 
 

Data dictionary

   
 

log

   

Maps

Mantigua.tif

Georeferenced Maps

 

Photos

 

Orthophotos

 

Source Map

Scale 1:25,000
Number of sheets
2
Contour interval
25ft and 100ft
Grid
British West Indies
Projection
Transverse Mercator
Spheroid
Clarke 1880 (Modified)
Unit of Measurement
Metre
Meridian of Origin
62 West of Greenwich
Latitude of Origin
Equator
Scale factor at Origin
0.9995
False Coordinates of Origin
400,000 m Easting; Nil m Northing
Year published
1962


Data Dictionary for Barbuda PGDM DEM Project

FolderName

FileName

Content

Attribute data

Bargrid

 

DEM in Raster grid

Cell size = 30.28m

     

# of rows = 681

     

# of columns = 546

Bartin

 

TIN layer

 

Info

 

System files

 

Shapefiles

barcoast.shp

Coastlines

 
 

barconto.shp

Contours

Htm (heights)

 

barroad.shp

Roads

 
 

barairport.shp

Airport

 
 

barponds.shp

Ponds

 
 

barmangr.shp

Mangroves

 
 

barcliff.shp

Cliffs

 
 

bar3dptz.shp

3D shapefile of points

 

Otherfiles

barbuda

Arcview project

 
 

barxyz.txt

XYZ in ASCII text format

 
 

barxyz.dbf

XYZ in DbaseIV format

 
 

Data dictionary

   

Maps

mbarbuda.tif

Georeferenced Maps

 

Photos

Mcodring.tif

Orthophotos

 

Source Map

Scale 1:10,000
Number of sheets 9
Contour interval 25ft
Grid U.T.M Zone 20
Projection Transverse Mercator
Spheroid Clarke 1866
Unit of Measurement Metre
Meridian of Origin 63 00' West of Greenwich
Latitude of Origin Equator
Scale factor at Origin 0.9996
False Coordinates of Origin 500,000 m Easting
Year published 1970


Data Dictionary for St. Kitts PGDM DEM Project

FolderName

FileName

Content

Attribute data

skgrid

 

DEM in Raster grid

Cell size = 33.335m

     

# of rows = 681

     

# of columns = 771

sktin

 

TIN layer

 

Info

 

System files

 

Shapefiles

skcoast.shp

Coastlines

 
 

skconto3.shp

Contours

Elevation

 

skspot.shp

Spot heights

Htm (heights)

 

sktrans.shp

Roads and railways

 
 

skdrain.shp

Drainage

 
 

skcliffs.shp

cliffs

 
 

sk3dptz.shp

3D shapefile of points

 

Otherfiles

St_kitts

Arcview project

 
 

skxyz.txt

XYZ in ASCII text format

 
 

skxyz.dbf

XYZ in DbaseIV format

 
 

Data dictionary

   

Maps

orthkitt.tif

Georeferenced Map

 
 

Stkitts.tif

Snanned map

 

Photos

ophbast.tif

Georeferenced photo

 
 

moldrcl.tif

Orthophotos

 

Source Map:

Scale 1:25,000
Number of sheets
1
Grid
British West Indies
Projection
Transverse Mercator
Spheroid
Clarke 1880 ( Modified)
Unit of Measurement
Metre
Meridian of Origin
62 West of Greenwich
Latitude of Origin
Equator
Scale factor at Origin
0.9995
False Coordinates of Origin
400,000 m Easting; Nil m Northing
Contour interval
50feet
Series
E803 (DOS 343)
Edition
1984


Data Dictionary for Nevis PGDM DEM Project

FolderName

FileName

Content

Attribute data

Nvgrid

 

DEM in Raster grid

Cell size = 28.05m

     

# of rows = 454

     

# of columns = 358

Nvtin

 

TIN layer

 

Info

 

System files

 

Shapefiles

nvcoast.shp

Coastlines

 
 

nvctour.shp

Contours

Elevation

 

nvspotht.shp

Spot heights

Htm (heights)

 

nvroads.shp

Roads

 
 

nvriver.shp

drainage

 
 

nvcorals.shp

Coral reefs

 
 

nv3dptz.shp

3D shapefile of points

 

Otherfiles

navis

Arcview project

 
 

nvxyz.txt

XYZ in ASCII text format

 
 

nvxyz.dbf

XYZ in DbaseIV format

 
 

Data dictionary

   

Maps

onevismp.tif

Georeferenced Maps

 

Photos

Gr53nv.tif

Georeferenced photos

 
 

O53nv.tif

Orthophotos

 

Source Map

Scale 1:25,000
Number of sheets
1
Grid
British West Indies
Projection
Tranverse Mercator
Spheroid
Clarke 1880 (Modified)
Unit of Measurement
Metre
Meridian of Origin
62 West of Greenwich
Latitude of Origin
Equator
Scale factor at Origin
0.9995
False Coordinates of Origin
400,000 m Easting; Nil m Northing
Contour interval
50feet
Series
E803 (DOS 343)
Edition
5 O.S.D. 1984