While the usefulness of GIS is evident in its diverse application to many aspects of natural resource management, the reliability of GIS as a spatial decision making tool depends upon the quality of the source data. Issues associated with data quality, error, and uncertainty in spatial databases have recently attracted the attention of researchers in the field. The quality of data is related to the accuracy of the information and the type and amount of error or uncertainty present in source information. Accuracy is associated with the true or correct representation of some real-world phenomenon while precision deals with the exactness of measurement, i.e., the number of significant digits used to measure some phenomenon. Error refers to the amount of deviation from the true value (or in a statistical sense the difference between the actual and observed values).