POSITIONAL DISTORTION IN GEOGRAPHIC DATA SETS AS A BARRIER TO INTEROPERATION

A simple model of positional distortion in vector databases is presented. Positions are distorted by the addition of a vector field. The model is compared to the familiar epsilon band, which is shown to seriously underestimate positional displacement. The model is calibrated against a set of street centerline databases for the Goleta, CA area, using matched points. Properties of the distortion field are determined, including the variograms of the x and y components. Using conditional simulation it is possible to generate a population of possible distorted positions, and thus to study the properties of the distortion under various forms of analysis, including propagation through GIS operations. The paper reviews several general strategies for interoperation of positionally distorted geographic data sets in the context of Intelligent Transportation Systems. One proposed strategy, the ITS Datum, is reviewed in detail. The paper concludes with a general discussion of interoperability of geographic data sets in the context of positional distortion. CHURCH, CURTIN, FOHL, FUNK, GOODCHILD, KYRIAKIDIS, NORONHA PAGE 2