Data Human_related GNV122

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The Estimated Population Density data set for Senegal was created as part of an exploratory modelling exercise at UNEP/GRID-Geneva, in co- operation with the Catholic University of Louvaine in Brussels, Belgium, and its Center for Research on the Epidemiology of Disasters (CRED). CRED along with the World Health Organization (WHO) and its Emergency Preparedness and Response Unit together launched in March 1986 the Consolidated Information System for Famine Management in Africa (CISFAM). A series of data sets were digitized and/or derived from existing data at GRID-Geneva in 1986-87, to provide demographic out- puts for use in the CISFAM project database created at CRED and WHO.

In the absence of detailed data, the development of a population density data layer for Senegal was accomplished using a very rough estimation technique. The latitude and longitude of major transportation routes and 118 towns in Senegal were digitized from 1:500,000-scale maps of the Institut Geographique Nationale (IGN) in Paris, France. All of the towns were assigned a rank from one (village) to five (metropolitan area), based upon the relative size of each as depicted on the IGN maps.

The Earth Resources Laboratory Applications Software (ELAS) was used on the Perkin-Elmer computer system of GRID-Geneva to develop six raster data layers, one of the transportation network and the others for each of the (five) ranked town sizes. Each gridded data layer was generated at 30 seconds of latitude/longitude (approximately one kilometer square) spatial resolution. The data layers for distances away from each town and road were then developed using the ELAS 'DIST' function. Next, the final estimated population density data layer was generated by the summation of each of these distances, indexed through tables with different weights for the roads and relative size of towns (shown in the chart below), using the ELAS 'DBAS' function.

The Estimated Population Density for Senegal covers the entire country, with an origin of 16 degrees 41 minutes 45 seconds North latitude, and -17 degrees 32 minutes 15 seconds West longitude, in the northwest (or upper-left) corner. It extends to 12 degrees 17 minutes 45 seconds North latitude, and -11 degrees 21 minutes 15 seconds West longitude in the southeast (or lower-right) corner. The projection is the GRID standard Plate Carree or Simple Cylindrical (a particular form of the Equirectangular). The data file size of 528 rows (lines/records) by 742 columns (elements/pixels/samples) thus comprises 382.3 Kilobytes (Kb), or approximately .4 Mb of data per file.

The reference for the above UNEP/GRID - CRED/CISFAM data set is as follows: "Guha-Sapir, Debarati, J.-P. Revel and M. F. Lechat. April 1987. CISFAM Phase One Report. University of Louvaine, Brussels, Belgium, 29 pages". This document is available in English or French.