This paper describes use of the global positioning system (GPS) in differential mode (DGPS) to obtain highly accurate longitudes, latitudes, and altitudes of 1,169 houses, 15 schools, 40 churches, four health care centers, 48 major mosquito breeding sites, 10 borehole wells, seven shopping areas, major roads, streams, the shore of Lake Victoria, and other geographic features of interest associated with a longitudinal study of malaria in 15 villages in western Kenya. The area mapped encompassed approximately 70 km2 and included 42.0 km of roads, 54.3 km of streams, and 15.0 km of lake shore. Location data were entered into a geographic information system for map production and linkage with various databases for spatial analyses. Spatial analyses using parasitologic and entomologic data are presented as examples. Background information on DGPS is presented along with estimates of effort and expense to produce the map information.
PIP: The global positioning satellite (GPS) network system is comprised of 24 satellites orbiting at an altitude of about 10,900 miles. The authors describe how a simple modification of GPS known as differential GPS (DGPS) can be used to produce a highly accurate base map in a tropical area. DGPS circumvents the effects of selective availability (SA) error, an intentional error component added for security purposes at each satellite, to yield a highly accurate position fix. This paper documents the use of DGPS to obtain highly accurate longitudes, latitudes, and altitudes of 1169 houses, 15 schools, 40 churches, 4 health care centers, 48 major mosquito breeding sites, 10 borehole wells, 7 shopping areas, major roads, streams, the shore of Lake Victoria, and other geographic features of interest associated with a longitudinal study of malaria in 15 villages in western Kenya. 70 sq. km were mapped, including 42.0 km of roads, 54.3 km of streams, and 15.0 km of lake shore. Location data were entered into a geographic information system for map production and linkage with various databases for spatial analyses. Spatial analyses using parasitologic and entomologic data are presented as examples. Less than $25,000 was spent upon this project, of which $15,000 was for hardware and software.