Submitted to Steven Stichter |
Submitted by Jacob Opadeyi |
October 20, 2000
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.
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:
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.
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.
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
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:
Below is the list of persons contacted:
Code |
Persons |
||
Antigua |
Alva Guishard, DCA |
1-268-462-6427 |
|
Rosemary Georges, Project Coord. |
1-268-460-9329 |
||
Philmore James, Fisheries Dept. |
1-268-462-6106/1362 |
||
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 |
||
David Keith, Project Coord. |
1-869-465-5634 |
||
Ken Parker, OAS Office |
1-869-465-2636 |
||
Dwight Francis, Survey Dept. |
1-869-662-2727 |
||
Nevis |
Lewis Newton, Planning Dept |
1-869-469-5521 ext 2040 |
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.
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.
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.
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.
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.
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:
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.
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:
Efforts should be made at eliminating these drawbacks in future works.
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 |
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
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 |
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
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 |
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
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 |
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