Over the past decade a considerable amount of interactive graphics software has been developed to maintain digital map files. Maintenance generally involves updating or changing feature representations, and the software used for this purpose usually focuses on manual adjustment and screen image verification of a change to a local region of a single map. Powerful interactive color graphics tools have made more sophisticated types of editing possible.

Map compilation, or conflation, may be accomplished by simultaneously manipulating the graphic images of two different digital maps of the same region in order to recognize matched features and differences more easily. Fast computer programs for rubber-sheeting one or both of the maps permit a user of a computer graphics workstation to align the maps in stages through successive approximation methods. After the maps have been aligned, the user may readily identify similar features on the two maps by overlaying one feature on the other. Features of one map which have no counterpart on the other map stand out; they become highlighted in isolation when different colors are used for the two maps.

With some limitations, the computer may be programmed to recognize matches. Mathematical relations of geometric position may be used to test for matches; and, when the tests are satisfied, corresponding features may be flagged automatically as matches. Similarly, features which have no counterpart on the other map may be identified by mathematical tests which measure their isolation; and they may be flagged automatically as unmatchable features. Displaying the matched, unmatched, and unmatchable features in different colors as they are identified permits further operator interaction in the compilation process.