Masters Theses

Date of Award

12-1975

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

M. E. Springer

Committee Members

F. F. Bell, J. R. Carter

Abstract

Information about soils has been available for several years, but only recently has its value for diversified planning been realized. Early uses of detailed soil map information was for farm planning. Now this information is being used for city, county, state, and regional planning. Location of airports, roads, and sanitary land-fills are now based upon information obtained from the soil maps. Although detailed soil survey maps and reports are available, the complexity of the information does not lend itself to wide-spread use where large geographic areas are involved. This study was designed to: 1. investigate the feasibility of computerizing soil map unit data; 2. investigate methods of producing computerized interpretations and potential uses of the com-puterized information for land planning processes; 3. produce single purpose computer line printer maps; 4. evaluate time and cost involved with data input, analysis, and computer mapping of soil interpretations; 5. investigate the feasibility of comprehensive resource analysis by combining soil map unit data with other types of resource information. The Bearden 7 1/2 Minute Quadrangle (Knox County, Tennessee) was selected as the analysis area because of its diverse physical and natural features. Examination of the soil maps showed it to be highly complex in terms of size of the smallest mapping unit and number of mapping units. The smallest mapping unit was approximately one acre in size, and there were 175 different soil mapping units. The next step involved selection of methods of data capture (digitization), data intensity (cell size) , and information presentation (display). Several different methods were considered, but a point sampling method exhibited results which appeared to be useful and practical. Cell size selection was based upon the constraint of the geodetic referencing system, the size of the smallest soil mapping units, time available to do the data capture and analysis, and cost of producing the interpretative displays. Four sizes of geodetic cells (those bounded by lines of latitude and longitude) were initially considered: 7.5 seconds (10.72 acres), 3.75 seconds (2.68 acres), 2.5 seconds (1.19 acres), and 1.875 seconds (.67 acres). Actual time and cost for data capture and analysis were unknown, but it was known that both increased as the cell size decreased. After a subjective evaluation of these con-siderations, cell sizes of 1.19 and 2.68 acres were chosen for comparison. Grids of geodetic cells of 1.19 acres and 2.68 acres were used for digitization of soil mapping unit information. A series of row and column coordinates were used to express each cell location from a common reference point (northwest corner of the quadrangle). Digitization involved entering a row-column coordinate and the corresponding soil mapping unit symbol on a coding sheet each time a different soil mapping unit was encountered in scanning a row of geodetic cells. After digitization, interpretive maps were produced for data validation using the MAPCLASS computer program. Validation of the soil data was done by visually scanning several interpretive maps to detect obvious errors. Less obvious errors were corrected by using interpretation patterns to locate cells that were miscoded. After errors were corrected, final line printer interpretive maps were produced. Choice of interpretations was based upon a subjective evaluation of diversified land planning. Depth to bedrock, slope gradient, potential flooding areas, predicted per-colation rates, and soil drainage classes were chosen as they are all important in decisions about construction feasibility, sanitary waste disposal, and wildlife and forestry management. Another interpretation—potential corn yields—was chosen to illustrate the use in agricultural applications. A time-cost comparison was performed to illustrate the economy of both cell sizes. For the Bearden Quadrangle (38,661 acres) it was found that the smaller cell size took 2.5 times longer to digitize and cost $522 more than the 2.68 acre cell. However, the advantages of the smaller cells are evident for interpretations of fine scale patterns (flooding, slope gradient). The smaller cell size more accurately defines areas that are small and irregular across the landscape. From these observations, the following conclusions were drawn; 1. Digitization of soil mapping unit data was feasible. 2. Single purpose and composite line printer maps could be produced which would aid in providing the basis for planning decisions. 3. Time-cost considerations make this process feasible provided the resulting information is utilized in planning. 4. The choice of cell size is dependent upon the user, but as smaller cell sizes are used, the costs increase proportionally. 5. Since data capture (input) is a major cost of this process, the cost effectiveness increases with the number of interpretations produced. For example, if only one interpretation was produced, it might be less expensive to produce a hand delineated map.

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