Showing papers on "Digital soil mapping published in 1979"

Soil surveys: review of data-collection methodologies, confidence limits, and uses

Abstract: The scientific basis of the soil survey is that the locations of soils on the landscape have a degree of predictability. Soil surveys are reasonably accurate and affordably feasible because this soil-landscape association possesses a degree of correlation that is high enough to allow inferences and predictions of soil behavior. The soil surveyor uses a working model of soil genesis on the landscape and tests it through observations. Inferences derived from these observations are extrapolated to the boundaries beyond which the inferences have been judged by the soil scientist to be invalid by virtue of changes in one or more of the factors (e.g., slope, vegetation, parent material) responsible for controlling soil genesis. In most areas, the natural scatter or range of soil properties and the variability of the soil-landscape precludes the delineation of taxonomically pure soil units. This results in inclusions of both similar and dissimilar soils within the soil-unit delineations. Soil scientists recognize these inclusions and describe them as part of the map unit. The composition and variability of soil map units are discussed with examples of how these map attributes can be quantified to provide confidence limits for predictions of soil behavior. It is emphasized that the primary objective of most soil surveys is not to map delineations having taxonomic purity but to provide the user with information as a basis for judgments about soil potentials and behavior for various land uses. Studies and experience have shown that the uniformity of such map units for interpretive pruposes is much higher than is their taxonomic purity. (Authors)

Landsat MSS Data as an Aid to Soil Survey - An Operational Concept

Abstract: With the urgency throughout the country to complete the modern soil survey at the earliest possible date, new techniques and tools are being devised to carry out the soils mapping program. One such new mapping tool is a series of maps, derived from Landsat data, showing the spectral characteristics of soils. Whereas Jennings County, Indiana was the first county in the nation to be mapped using aerial photographs as base maps, Jasper County, Indiana is the first county to be mapped using spectral maps as an aid in. the county soil survey program. These spectral maps depict the pattern and boundaries of the soils occurring throughout the landscape of Jasper County. The spectral information was produced using computer-aided analysis (LARSYS) of Landsat-l multispectral scanner (MSS) data collected on 9 June 1973. Prior to analysis, the Landsat data were geometrically corrected and registered to aerial photography (1:15,840) collected for the USDA/Soil Conservation Service on 3 May 1976. Soil parent material boundaries visually interpreted from the Landsat imagery were used to stratify the county and classify spectral responses representing various soils within unique parent material areas. Correlation of the spectral responses with soil characteristics was accomplished by comparing the spectral maps with con~ ventionally prepared soil maps for randomly selected quarter sections throughout the county. Correlation of the spectral responses with soil characteristics such as surface color, surface texture, organic matter content and soil drainage was possible. The final spectral maps were correlated only with soil drainage characteristics since this correlation proved to be most consistent. The mapping of Jasper County is being carried out on half tone positive mylar which show the aerial photographic image of the mapping area. These mylar images can be overlaid on the spectral maps, thus allowing the soil scientist the benefit of both conventional aerial photography and the soil spectral characteristics for use as guides in delineating . map unit boundaries. The use of the soil spectral characteristics should greatly enhance the efficiency of producing a higher quali ty soil survey. 24