Doctoral Dissertations

Milton Allen

Date of Award

3-1984

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

M.E. Springer

Committee Members

F.F. Bell, J.R. Carter, G. Lessman

Abstract

Basically, two questions prompted this study: (1) is a digital soils data base needed? and, if so, (2) which system or systems can handle and present soils information most efficiently and effectively?

Objectives were: (1) to identify needs and problems of a digital soils database, (2) to evaluate many systems for handling soils information, and (3) to choose systems and use them to demonstrate the capabilities of computer-assisted spatial analysis and mapping systems in handling soil information.

Computerized soil surveys and digital soils data bases are needed because soils information is used in the planning process for nearly all types of development. Since original soil surveys may be complex, simplified presentation should be directed to each of many users.

The needs and problems surrounding the development and use of a digital soils data base were assembled. On 55 systems out of more than a hundred systems as much information as possible was assembled from published literature, company brochures, and response to questionnaires. Questionnaires were returned from 50 Soil Conservation Service (SCS) state offices, 30 Land Grant Universities, and 4 SCS Technical Service Centers.

To demonstrate how data are stored, manipulated, and retrieved from a computer-assisted system, the two systems chosen for further consideration and extensive testing were the Map Information Assembly and Display System (MIADS) and the Information Manipulation System for Grid Cell Data Structure (IMGRID). MIADS was used by the SCS state office in Nashville, Tennessee, and TVA's Natural Resource Service at Norris, Tennessee, had IMGRID. MIADS had interactive editing capabilities; IMGRID did not.

The two systems were tested on a five minute (approximately 6900 hectares) portion of the Concord Quadrangle covering parts of Loudon, Knox, and Blount counties in Tennessee. These computer-assisted systems were used to join soil survey information from three counties into one project area. Grid cells of 1.08 hectares (2.68 acres) were used for both systems. Most of the encoded data were taken from soil surveys. However, land use was determined partly in the field and partly from interpretations of 1975 aerial photo graphs and a 1968 revised topographic map. The capabilities of MIADS and IMGRID were demonstrated by using encoded soils data along with other information from topographic maps. Interpretive and single factor maps such as suitability for farmland, depth to bedrock, land capability class, and slope were produced to show how detailed soils information can be simplified for a particular user.

Both MIADS and IMGRID were used for combining land use with soil interpretations to show how different kinds of farmland are used. IMGRID was used to combine proximity to roads, streams, and residential development with interpretations from soils to show suitable landfill sites. Potential landfill sites not conflicting with development were also displayed with IMGRID, but this could not be done with MIADS.

Patterns on IMGRID maps are easier to see than those on MIADS line printer maps because of the overprinting capabilities of IMGRID. However, IMGRID patterns become more difficult to see as the number of classes increases. Maps with 3 to 5 classes are much easier to comprehend than those with 10 or more classes.

Of the two systems selected to demonstrate the capabilities of computerized systems, IMGRID was capable of performing more analyses than MIADS. Thus more kinds of information could be handled and presented using IMGRID. However, because of the greater volume of data processed by IMGRID the total cost of encoding, keypunching, and other operations was greater than for MIADS. Direct comparison of costs for the same operation could not be made because the way of charging for processing differed between the SCS computing center in Nashville and the TVA computing center in Morris.

Evaluation of the maps and supporting materials produced by the two systems leads to the conclusion that IMGRID is definitely a more effective system for processing resource information. Further investigation of costs would be needed to determine how much is saved by MIADS.

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