The purpose of TdhGIS is to perform spatial analysis of data based on vector defined geometric data. This may include : Allocating point data to polygons. (e.g. assigning structures to hydrological basins). Allocating polygon data to other polygons. (e.g. allocating population data by census block to political boundaries). Creating thiessen polygons (e.g. for all hospitals within a state, define the areas where a particular hospital is closer than any other). Creating data contours (e.g. create lines of equal ground elevation based on a set of elevation points). Creating contour polygons (e.g. define the area where average rainfall exceeds a selected value based on weather station data). Read More