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Population Density GIS Database for 52 counties of Montana, Idaho, and Washington
Image of Poster:
Example showing detail, displayed as density classes along with public or uninhabited private lands:
This population density grid for a 52-county area around the western portion of USFS Region 1 was created via dasymetric mapping process from U.S. Census 2000 data and other GIS layers.
Dasymetric mapping is a GIS
process whereby the output mapped areas are not identical to the input enumeration unit. In this case,
spatial population density is refined from the enumeration unit (Census Blocks) by use of other GIS filters.
The numbers of people counted by the 2000 Census (at the finest Block level) were reassigned to smaller
map units in a sequence of filtering steps. First the boundaries of inhabited areas were restricted by
eliminating all public lands, Plum Creek Timberlands, water features, certain uninhabited land cover types,
land of extremely steep slope, and other local lands designated by the Census itself as non-populated at the
Block level (example: urban commercial zones). Excluding these areas in this dasymetric mapping process has
the largest effect on the overall new densities in the final product, since density on a per area basis is
then far different, particularly in areas with high levels of public land ownership -- common in these 52 counties.
Actual population counts for each Census Block then were redistributed with relative weighting according
to the underlying land cover/land use (classified from satellite imagery), and resulting densities were calculated.
Population is redistributed on a per-area basis. This is very important: for example, one doesn't simply assign
35% of the count to Urban covertype region, even if there is just a sliver of Urban. Instead, the area of Urban
is calculated and the count is redistributed on a per-area basis with a relative formula. ">
dasy52_metadata.html - Click to view metadata
Project complteion date: June 30, 2002
| Principal Investigators | Roland L. Redmond |
| GIS Analysts | Jim Schumacher |
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