ABSTRACT
Whatever else they may convey, all spatial data possess coordinate locations. Each geographic entity recorded in a GIS must have an identifiable spatial signature among its properties. As a GIS must be relied upon to integrate, analyze and display independent collections of spatial data, it should possess means for coping with variability in the quality of coordinate and other information in the features, layers and themes it records, according to their nature, source and purpose. This is usually not possible, hence rarely done.
