Tuesday Term of the Week: Overlay

Looking for specific topics?



Try sorting by categories

Or, view our archive

There are many benefits to digital mapping. It gives users the ability to compare different kinds of information at one time. One of the ways this works is through overlay, a spatial operation in which two or more map layers at a common scale and coordinate system are superimposed, either digitally or on transparent material, for the purpose of showing the relationships between features that occupy the same geographic space. This is a vital technique when analyzing land and property assessments. Individual geographic features can be completely contained within other features, or can partially overlap one another. The area of overlap creates a composite region made from the intersection of the features. Map symbology is also considered an overlay, containing informational items like a legend, feature labels, icons, scale bars, coordinate grids, direction arrows and colors or fill patterns. Symbology is typically placed on top of the other map layers.