City plans and large-scale maps are used to determine areas of highest population density. The entire urban area is then encompassed by circles whose radii range from 0.3 to 2.0 nautical miles. Circles are identified by the coordinates of their centers. Population estimates are made for each circle and then projected for 12 years. The population of any urban agglomeration summed with the total rural population of the rectangular area comprises the area's total population.
Density is computed using the area of the rectangle, correcting for water coverage.
Projected Population Data Urban and rural populations are projected by extrapolating the rate of change in their ratio to total country population. In 1993, IPC completed work for the United States country database based on the 1990 census. Map images are accessible via links within Leddy's article, or by accessing this image library . To browse the entire ISSC report, click here . This database contains more demographic data for the countries in the world.