In geographic analysis, what does the term 'overlay' refer to?

In geographic analysis, the term 'overlay' refers to the process of combining multiple maps or datasets to analyze spatial relationships and patterns. This technique allows geographers and GIS professionals to layer different types of information, such as demographic data, environmental data, or land-use data, to gain insights about how these elements interact in the geographical space. By overlaying different datasets, users can identify correlations, assess impacts, and make informed decisions based on the combined information.

For example, by overlaying a map of population density with a map of public transportation routes, one can examine which areas have high population but low access to transportation, thereby highlighting potential needs for service improvement. This analytical capability is central to the functionality of GIS, enabling more comprehensive analysis beyond what single maps can provide.