Vector overlay

Some overlay operations, especially Intersect and Union, are implemented in all GIS software and are used in a wide variety of analytical applications, while others are less common.

Warren Manning appears to have used this approach to compare aspects of Billerica, Massachusetts, although his published accounts only reproduce the maps without explaining the technique.

[4] The first true GIS, the Canada Geographic Information System (CGIS), developed during the 1960s and completed in 1971, was based on a rudimentary vector data model, and one of the earliest functions was polygon overlay.

[7] Carl Steinitz, a landscape architect, helped found the Harvard Laboratory for Computer Graphics and Spatial Analysis, in part to develop GIS as a digital tool to implement McHarg's methods.

Chrisman and James Dougenik implemented this strategy in the WHIRLPOOL program, released in 1979 as part of the Odyssey project to develop a general-purpose GIS.

[9] This system implemented several improvements over the earlier approaches in CGIS and PIOS, and its algorithm became part of the core of GIS software for decades to come.

Since the original implementation, the basic strategy of the polygon overlay algorithm has remained the same, although the vector data structures that are used have evolved.

The most common are closely analogous to operators in set theory and boolean logic, and have adopted their terms.

Each of the criteria can be considered boolean in the sense of Boolean logic, because for any point in space, each criterion is either present or not present, and the point is either in the final habitat area or it is not (acknowledging that the criteria may be vague, but this requires more complex fuzzy suitability analysis methods).