GIS a set of analytical procedures applied with a GIS —note there are three categories of spatial modeling functions that can be applied to geographic data objects within a GIS: (a) geometric models (such as calculation of Euclidean distance between objects, buffer generation, and area and perimeter calculations); (b) coincidence models (such as polygon overlay, line on polygon overlay, and point on line overlay); and (c) adjacency models (such as pathfinding, redistricting, and allocation); all three model categories support operations on geographic data objects such as points, lines, polygons, TINs, and grids; functions are organized in a sequence of steps to derive the desired information for analysis This definition last updated 10/07/2008