Dahlberg, Richard E.||Krmenec, Andrew J.
M.S. (Master of Science)
Department of Geography
Real property--Maps||Real property tax||Digital mapping
Tax map data were converted from hardcopy to digital form using three tax map conversion methods: digitization and transformation; digitization, transformation, and rubbersheeting; recompilation, digitization, and transformation. Conversion methods were independently applied to two coordinate control data sets. The first was constructed from survey data collected using traditional and global positioning system (GPS) surveying techniques. The second was constructed from map features on USGS 7.5-minute maps. The accuracy of the products from these conversion methods was evaluated along with the influence coordinate control data have on this accuracy and the replicability of the conversion methods. The accuracy of the conversion methods and the influence of the control data were measured by comparing conversion products with two parcel map control data sets. One parcel map was constructed from the survey coordinate control data. The second was constructed from the USGS map feature control data. Public Land Survey System (PLSS) comer positions, parcel comer positions, parcel dimensions, and parcel areas were used in this comparison. These parcel characteristics were identically coded across the conversion method products and parcel maps. The Euclidean distance metric was used to calculate positional differences in PLSS and parcel comer positions. Absolute differences were calculated for parcel lines and parcel areas. Arithmetic means, standard deviations, and coefficients of variation were calculated for these differences and used to analyze the accuracy of the conversion method products and the influence of the coordinate control data. The conversion method which used rubbersheeting and survey control data produced the best positional, dimensional, and areal accuracies. Recompilation produced the worst regardless of coordinate control data. The remainder produced similar results. The influence of the coordinate control data was seen in all aspects of parcels described by aliquot part descriptions. The coordinate control data influenced only the positional aspects of metes and bounds described parcels. The coordinate control data did not influence the replicability of the conversion methods, but did influence the accuracy of the results from those methods. The study area for this research is located in Kingston Township, DeKalb County, Illinois. It consists of four PLSS sections which remain well defined on the landscape. The primary land use within the study area is agriculture. The terrain is low to moderately rolling with elevation differences throughout the study area of approximately 330 feet.
Carlson, Christine L., "A comparative analysis of selected tax map conversion methods" (1994). Graduate Research Theses & Dissertations. 97.
xii, 93 pages,  pages of plates
Northern Illinois University
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