using the “map algebra” arcgis toolbox function to - tmacog.pdfVIP

Using the “Map Algebra” ArcGIS Toolbox Function to Identify Criteria Locations Map Algebra is used when you want to find the places where several layers of data overlap the most. Map Algebra allows the user to use a process called suitability mapping to try to find locations that are “ideal” or “not ideal” for a process or structure. For example, if you want to try to find the best place to locate a sewer, planners have several criteria that they use as places that are ideal and places they want to avoid. Suitability mapping allows them to look at an entire area and weed out locations that are not suitable. The final product is ONLY as good as the criteria. The more criteria you have, the better your suitability map will be. Steps 1. Turn on spatial analyst extension. 2. Choose criteria layers and add them to the mxd. Vector layers must be of the polygon shapefile type, must already be raster data, or must be able to be converted to raster layers (i.e. line and point shapefiles can be converted to raster data by using the Euclidean distance function – last picture shows a Euclidean distance from points). The Euclidean distance tool is found in Spatial Analyst Tools  Distance  Euclidean Distance. The tool will automatically choose concentric distances or you can put in the maximum distance and it will figure it out. ALWAYS click Environments (tab at the bottom)  Processing Extent  Choose the extent of your map. This will fill in all the space. The reason for doing this is the final raster will ONLY be the size of your smallest raster extent (e.g. if a layer is 1000 pixels x 1000 pixels and another is 500x500, your final image will be 500x500). 3. Rasterize. All data must be converted to raster layers. All of the Raster conversion tools are in Conversion Tools  To Raster  Polygon to Raster. Choose Maximum Combined Area for cell assignment