GIS Overlay*

A Geographic Information System allows its users to measure and display spatially-referenced data. The ability to measure data, variable over space, enables users to analyze the differences between places. For example, we can compare population across census tracts in Erie County to examine where the County's population is most dense. If we want to try to understand why clusters of high or low population exist, we can then overlay (place another layer of information on top of our information on population) another data set, such as vacant lots or highways. By overlaying another data set, we can then begin to visualize and argue for a relationship between variables--however, much more research would need to be done in order to fully understand this relationship! It is important to remember that GIS is a powerful tool for use in understanding our environment and society and is also only as wise as its user.