Overlay

From Wiki.GIS.com

Overlay is a GIS operation in which layers with a common map base are joined on the basis of their occupation of space. (Keith C. Clarke, 1997).

An overlay creates composite maps by combining different data sets. You can use overlays to superimpose a road map over a map of local wetlands, or multiply and add attributes of different values to determine averages and co-occurrences.

Raster and vector models differ significantly in the way overlay operations are implemented. Overlay is usually more efficient in raster-based systems. However, hybrids of both raster and vector overlays exist.

[edit] References

• Peterson, Dr. Michael P., GIS Analysis Functions, GEOG 4050/8056: Geographic Information Systems I, University of Omaha. Accessed 20 September 2011.

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