Setting Things Up
With ArcCatalog make a file geodatabase named Redlands.gdb in
Start ArcMap. To a blank map add the data files ROADS.shp and STUDY_AREA.shp from the Park_Data folder. Make sure that ROADS is at the top of the T/C. Save the resulting map as Site_Park.mxd in the Park_Data folder. All rasters you make should go into this file geodatabase.
____ 2. Examine the Site_Park T/C entries: The study area is a simple, single polygon representing the Redlands, California, area. ROADS is a line file. Each single feature in ROADS is an amalgamation of all the roads of a given type in the study area.
____ 3. Change the mapping units and the display units of the data frame to Feet.
____ 4. Set Environment Variables: Geoprocessing > Environments. Leave the coordinate system undefined. Make the Processing Extent Same as Layer “STUDY_AREA.shp.” Under Raster Analysis Settings, set the cell size to 150 (under As Specified Below). Click OK. Resave the mapfile Site_Park.mxd, in case you have to come back to this point.
Now that setup is complete and you begin thinking about the problem, a couple of issues might come to mind.
(a) How are you going to identify the off ramps?
(b) How are you going to exclude cells that have no roads, and cannot be traversed? Recall that your previous experience has been with rasters in which any cell could be traversed.
As to (a), you will be able to select the ...