Problem: Human population distributions are commonly displayed using decennial census data. However, these data are aggregates of geographic units (census tracts or block groups) whose boundaries do not always reflect the natural distribution of human populations. A dasymetric mapping technique is one potential solution for mapping population density relative to residential land-use. Dasymetric mapping depicts quantitative areal data using boundaries that divide the area into zones of relative homogeneity with the purpose of better portraying the population distribution.
Objective:The San Francisco Bay region’s population has grown from approximately 6 million inhabitants in 1990 to 6.8 million inhabitants in the year 2000, a 12% increase. Spatial analysis of the nine-county region is necessary in order to conceptualize urban growth patterns essential for land-use planning and urban-growth modeling. We are developing a method for generating a surface-based representation of demographic data using dasymetric mapping techniques. Our objectives are to (1) use the USGS National Land Cover Datasets for 1992 and 2001 to classify homogeneous zones of high-intensity residential, low-intensity residential, non-urban land-cover; (2) use other information such as slope, land ownership, and transportation to exclude uninhabited areas; (3) create a 30-meter surface grid of population density based on the relative difference in population densities among the urbanization classes and the percentage of total area of each census-block-group occupied by urbanization classes; and (4 ) visually and statistically represent the population-density results for the region for 1990 and 2000 with static maps and raw, downloadable data.
Future Work:The dasymetric mapping technique that we have developed can be easily applied to other regions. Currently, daytime/nightime populations are being estimated for the Oregon Coast, for emergency response in the event of a Tsunami.
