The European Commission Joint Research Centre (EC JRC) and the Columbia University Earth Institute Center for International Earth Science Information Network (CIESIN) created a 250-meter resolution population grid. Residential population estimates for 1975, 1990, 2000 and 2015 were generated by disaggregating census or administrative unit population data and re-mapping them to grid cells.
The distribution and density of built-up area (from the Global Human Settlement Layer) informed the re-mapping of the population data. The model used raster-based density mapping relying on the Global Human Settlement – Built-Up Area data to define the distribution of people and inform the respective density. The Built-Up grid is the distribution of built-up areas displayed as the proportion of occupied area within each cell. Population estimates came from country-based census data and administrative polygons with estimated residential populations. Population grids were created using a volume-preserving density mapping approach: given population data and built-up area data:
A. If the polygon generates 250 meter cells and contains built-up area data, disaggregate the population in proportion to density of built-up area;
B. If the polygon generates 250-meter cells and does not contain built-up area data, disaggregate the population using areal weighting;
C. If the polygon does not generate its own 250-meter cell, convert polygon to point (centroid within), sum al points within a cell, and sum to a mosaic of A and B.
Option C was required because some populated source zones (polygons) were smaller than a 250 x 250 meter cell. This process preserved the full resolution of the Gridded Population of the World data set. All data came from the respective years. For access to the full data set and additional information, see the Learn More link.
GHS Population Grid (LDS)
For 1975, greater uncertainties in estimating small-scale populations farther from the census year combine with larger difficulties in mapping built-up (from lower-resolution Landsat MSS sensor) to make this surface less reliable. A consequence of C-points is the allocation of population from these (typically small) polygons to only one cell, and occasionally a slight displacement of population to neighboring 250 m cells. Quality control was conducted to ensure that all input population was disaggregated and totals were preserved.
European Commission, Joint Research Centre (JRC); and Columbia University, Center for International Earth Science Information Network (CIESIN). 2015. "GHS Population Grid, Derived from GPW4, Multitemporal (1975, 1990, 2000, 2015)." Dataset. pid: http://data.europa.eu/89h/jrc-ghsl-ghs_pop_gpw4_globe_r2015a. Accessed through Resource Watch, (date). www.resourcewatch.org.
1975, 1990, 2000, 2015