SLOPE CLASS MAPS FROM SOIL SURVEY AND DIGITAL ELEVATION MODELS

Special-purpose land use maps based on slope attributes from digital e levation models (DEMs) often are produced with geographic information system technology. Field verification is lacking for accuracy and prec ision of computer-generated slope class maps from 10- and 30-m DEMs, a standard USDA (1:24 000) soil survey, and field-measured slopes. Two 16-ha sites in Atchison County, Missouri, were selected, flagged on 10 -m grids, and the slope was field measured for each grid cell. The fie ld-measured slope class maps were templates for cell-by-cell compariso ns with the computer-generated slope classes. More than 50% of the are as were classified into correct slope classes with 10-m DEM maps. The 30-m DEM maps were 30 and 21% correctly classified in the two study ar eas. Two iterations of low-pass filters increased the accuracy of the 10-m derived maps, but decreased the accuracy of one 30-m derived map. Soil survey techniques correctly classified >30% of each area, but di d not capture landscape heterogeneity. The GIS-produced maps underesti mated slopes on convexities and overestimated slopes on concavities. S lope class maps from 10-m DEMs have potential use for soil survey and land use planning.