Naming Conventions

The grids generally follow a naming convention that reads: geographic unit, type, date, adjustment, rounding. These conventions are explained below.

GEOGRAPHIC UNIT

Regional grids have a two-letter prefix as described below. The country-level grids have a three letter prefix that is the ISO letter code for the country. The three letter country codes together with the full name of the countries are listed in the file cntry_ISO.csv on the ftp site under /pub/gpw/.

gl Global
af Africa
as Asia
eu Europe
na North America
oc Oceania
sa South America

TYPE

The grid type describe which variable the grid stores as values.

areag	Land area of each grid cell in square kilometers
p	Estimated population count in each grid cell
ds	Population density based on count grids divided by area grids (persons per square kilometer).

DATE

Year that the grid data represents.

90	estimates for 1990
95	estimates for 1995

**Please note** Almost all of the land area (areag) grids have no date. This is because, for the majority of the countries, only one set of boundaries were used for the two dates. However, the global, North American and Canadian grids have two area grids, one for 1990 and one for 1995. This is because two seperate input coverages for Canada were used in the gridding process (one for 1990 and one for 1995), leading to slightly different areas in the two dates. All other countries used only one input coverage, thus the areas do not vary between 1990 and 1995.

ADJUSTMENT

National-level population estimates from the United Nations have been used to adjust the population totals for each country. The difference between the UN estimate and the source data estimate of total population for each country was used to calculate an adjustement factor. This factor was applied to the grids at the national level. Both adjusted and unadjusted grids are available.

g	unadjusted estimates
ag	adjusted estimates

ROUNDING

The grids are available with values that have been rounded to the nearest whole number and with floating point (decimal) values. The BIL format grids have been rounded to the nearest whole number and are stored as 4-byte integers (whole numbers). The ArcInfo exchange format grids are stored as floating point (decimal) values.

i where present, the suffix indicates that the grid has been rounded to the nearest whole number

EXAMPLE

asp90g	is the grid of Asia containing population counts for 1990, unadjusted
asp95ag	is the grid of Asia containing population counts for 1995, adjusted to match the UN totals
asds90g	is the grid of Asia containing densities for 1990, unadjusted.
asareag	is the grid of Asia containing the land area for each grid cell
asareagi	is the grid of Asia containing the land area for each grid cell in BIL format (whole numbers)