D1 through D3 DESCRIPTION:
Global population fields were constructed for the year using country-level demographic statistics from the World Resources Institute (WRI) Earth Trends database (http://earthtrends.wri.org/). The urban and rural population data sets were developed by spatially distributing the WRI 2000 country level population data among DMSP-OLS nighttime stable-lights imagery (Elvidge 1997a) and ESRI Digital Chart of the World populated places points (ESRI 1993). Country-level urban population was evenly distributed among the DMSP-OLS city lights data set at 1-kilometer grid cell resolution with detectable lights in at least 10 per cent of the cloud free bservations (Elvidge 1997b). Where available, the spatial extents of major city locations with known demographic data (Tobler 1995) were superimposed in the DMSP-OLS city lights data set to enhance the accuracy of the urban population distribution. Rural population was spatially distributed equally among the DCW populated places points falling outside of the DMSP-OLS city lights extent. Total population is simply the sum of urban and rural population data sets.
(D1) Urban_pop_2000.asc = Urban population in people per grid cell (30-min) for the year 2000. Primary source: Vorosmarty et al (2000).
(D2) Rural_pop_2000.asc = Rrban population in people per grid cell (30-min) for the year 2000. Primary source: Vorosmarty et al (2000).
(D3) Total_pop_2000.asc = Total population in people per grid cell (30-min) for the year 2000. Primary source: Vorosmarty et al (2000).
Elvidge, C., K.
Baugh, E. Kihn, H. Kroehl,
Elvidge, C., K. Baugh, E. Kihn, H. Kroehl, E. Davis, C. Davis. 1997b. Relation between satellite observed visible-near infrared emissions, population, economic activity and electric power consumption. Int. J. of Remote Sensing, Vol. 18, No. 6, pp 1373-1379.
The Digital Chart of the World. 1993.
Environmental Research Systems Institute, Inc.
Tobler, W., U. Deichman, J. Gottsegen, and K. Maloy, 1995. The Global Demography Project, Technical Report TR-95-6, NCGIA,