ISLSCP II -- Global Population of the World

ISLSCP Initiative II

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Global Population of the World

Global Population of the World (GPW) translates census population data to a latitude-longitude grid so that population data may be used in cross-disciplinary studies. Over 127,000 administrative units and population counts were collected and integrated from various sources to create the gridded data. In brief, GPW was created using the following steps:

Population data were estimated for the product reference years, 1990 and 1995, either by the data source or by interpolating or extrapolating the given estimates for other years.
Additional population estimates were created by adjusting the source population data to match UN national population estimates for the reference years.
Borders and coastlines of the spatial data were matched to the Digital Chart of the World where appropriate and lakes from the Digital Chart of the World were added.
The resulting data were then transformed into grids of UN-adjusted and unadjusted population counts for the reference years.
Grids containing the area of administrative boundary data in each cell (net of lakes) were created and used with the count grids to produce population densities.

As with any global data set based on multiple data sources, the spatial and attribute precision of GPW is variable. The level of detail and accuracy, both in time and space, vary among the countries for which data were obtained.

Data Provider: Deborah Balk, Uwe Deichmann, Gregory Yetman

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(ISLSCP II Disc #1)
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File Information

This data set consists of three data types: land area, population counts, and population density. The files are global and are at 3 scales -- 1-degree ("1deg", 360 x 180), 0.5 degree ("hdeg", 720 x 360), and 0.25 degree ("qdeg", 1440 x 720). The data file is in ASCII and space delimited. The following files are included in the compressed PKZip archive files:

Land Area (gpw_land_area_xdeg.zip)
gpw_land_area_xx.asc: Global gridded land area (square km of land per cell). xx can be qd, hd, and 1d, denoting a spatial resolution of 1/4, 1/2 and 1 degree, respectively. NOTE how there is less land area near the poles, because of the "stretching" of the pole region due to the equal-area projection.

Population Counts (gpw_populations_counts_xdeg.zip)
gpw_pop_counts_xx_YYYYa.asc: Global gridded population counts (persons per square km per cell). xx can be qd, hd, and 1d, denoting a spatial resolution of 1/4, 1/2 and 1 degree, respectively. YYYY is the year (1990 or 1995), and if there is an "a" after the year, the data has been adjusted by the United Nations.

Population Density (gpw_populations_density_xdeg.zip)
gpw_pop_density_xx_YYYYa.asc: Global gridded population density (persons per cell). xx can be qd, hd, and 1d, denoting a spatial resolution of 1/4, 1/2 and 1 degree, respectively.

Related Pages:
ISLSCP Initiative II Home
General Data Overview
Socioeconomic Data Overview
Global Populaion of the World

Revision Date: April 23, 2003