If you’ve not heard the term "GIS" before, let’s define it. The U.S. Geological Survey offers a short definition at its website. It says that a GIS is, “A computer system that analyzes and displays geographically referenced information. It uses data that is attached to a unique location.” The key idea there is that different physical locations in a city have different features. Any given spot could have a fire hydrant, a road, a flood plain, a conservation area, a park, a single family house, or dozens of other attributes. The possibilities are nearly endless. The power of GIS is that each of these features are mapped on a separate GIS layer. Think of GIS layers as individual map sheets that have been digitized and can be superimposed on top of each other. A GIS map can be tailor made to the task at hand by layering the digitized map sheets. For example, GIS would allow you to create a map showing all low density residential lots (layer 1) within 1,000 feet of a city park (layer 2) that can be accessed with existing sidewalks (layer 3) on collector or local roads (layer 4).