Geographic Information System (GIS) Applications in Alabama Soil Survey.
Zamir Libohova, Stephon Thomas, Jerome Langlinais, Charles Love, and George Martin. USDA-NRCS, 420 Hackberry Lane/P.O.Box 861482, Tucsaloosa, AL 35486
The NRCS Alabama Soil Survey Program is rapidly moving towards digital products. New digital technologies including Geographic Information System (GIS), Global Positioning System (GPS), Remote Sensing, are being introduced and extensively utilized. The objective of this paper is to demonstrate the use of digital technology in (i) initial and updating soil survey and (ii) digital soil survey publications in Alabama. In the initial and update soil surveys, ArcMap, ArcView, OrthoMapper, and 3D Mapper software are being used to combine information from topographic maps (USGS 7.5 minute quadrangle), aerial photographs, infrared aerial photographs, geological maps, plat books, etc. Various thematic maps used during field soil mapping are generated through digital transformations. Maps combining topographic lines, aerial photograph, and shaded relief from Digital Elevation Models (DEMs) help soil scientists to initially identify slopes (gradients and shapes), elevation, relief, and landscapes used for delineating and establishing map units. Map unit delineations are further adjusted in the field based on aerial photographs and GPS to reflect the actual landscape positions. The adjusted map unit delineations are transferred from the topographic field map to a digital format through two major steps. In the first step, the soil lines are transferred from the topographic image to a Mylar. In the second step the soil lines are transferred from Mylar to a digital form. Map unit delineations or the existing soil survey maps are scanned to create “.tiff” files to be orthorectified or georeferenced using ArcMap and Orthomapper. Using ArcGIS digitizing tools polygon coverage and shape files with attributes for map unit names, acres, and other soil properties are created. Estimated time for creating geodatabase, digitizing, and attributing per 7.5 USGS quadrangle (1:24000) varies from 40 to more than 200 hours depending on the detail of mapping and GIS knowledge of the user. When conducted or supervised by soil scientist these transfers assure quality control, because the soil lines are viewed in detail and missing and incorrect symbols are spotted and fixed easily. The new digital soil maps are being used as a basis for producing digital Soil Surveys in Alabama. The Soil Surveys can be uploaded to the web and made available to internal and external customers through CDs or downloaded directly to their PCs. Currently 20 Soil Surveys are available on-line in a “.pdf” format at: http://soils.usda.gov/survey/online_surveys. Of the 67 Alabama counties, 47 Soil Surveys are SSURGO Certified, meeting all standards and specifications for a digital product (Tabular and Spatial). The goal is to have all published Soil Surveys by 2007 in a spatial and tabular digital format at: http://soildatamart.nrcs.usda.gov. These Soil Surveys are also available on the newly launch Web Base Soil Survey web site at: http://websoilsurvey.nrcs.usda.gov/app.