This page describes the process by which the images used in this web site were generated. It also enumerates some of the disclaimers to bear in mind while exploring the maps. Inquiries should be directed to
Daniel Karnes
Geographic Information Systems Curricular Computing Consultant
Peter Kiewit Computing Services
6224 Baker/Berry
Dartmouth College
The elevation data used to generate the hillshade layer comes from GTOPO30. This is "a global digital elevation model (DEM) resulting from a collaborative effort led led by the staff at the U.S. Geological Survey's EROS Data Center in Sioux Falls, South Dakota. Elevations in GTOPO30 are regularly spaced at 30-arc seconds (approximately 1 kilometer). GTOPO30 was developed to meet the needs of the geospatial data user community for regional and continental scale topographic data." (GTOPO30 Readme) Thus, it is only usable when viewed at medium and small scales (smaller than 1:500,000). The hillshade layer was nonetheless placed in the first one or two high-resolution images for each of the bays and gulfs presented here, where the viewer can see that indeed at that scale the hillshade pixels are pretty darn blocky. But it's the highest-resolution eleveation dataset available for this part of the world, until the Shuttle Radar Topography Mission data are processed.
Similarly, the hydrography and population point data are from the Digital Chart of the World. This dataset also has a number of limitations in usability and accuracy. The source maps from which the DCW was compiled were Operational Navigation Charts used in aviation, and the map scale was 1:1,000,000. That is a pretty small scale, and when the maps of bays and gulfs are viewed, the user will note that a number of rivers seem to just end. The DCW coding for population points also did not have any indication of population counts, so all the populated place symbols are identical.
The classified imagery of Lake Victoria WH and non-WH was obtained from the principal author of the report, Tom Albright. Four bays and gulfs in Lake Victoria, and one of the lakes in the Kagera River Basin, were masked out and individual images for each date analyzed in the report were extracted from the set of classified imagery. These layers were then processed in ArcGIS version 8.2 to produce GIF images that could be placed onto a Web image server.