Assignment: Calling ArcGIS from Python

1. Processing Rasters

Create a Python script that will take a DEM and:

• Clip a DEM to a specified area (you may want to implement this last as it is the trickest part)
• Fill the sinks in the DEM
• Create a slope raster
• Create an aspect raster
• Create a raster with the slope betwen 10 and 20 percent and the aspect between 135 and 225 degrees (facing south)

Below is some code to get you started. Notice that in one function call you'll specify an input and output file path while in another, ArcGIS returns a raster "object" which you then save to a file. You'll need to change the file paths and you'll have to determine the format and values for the "clipping bounds".

Note: Don't worry about the final raster calculation ending up with nothing in the raster. I am only concerned about you getting the code functional.

import arcpy # connect to ArcGIS

arcpy.CheckOutExtension("Spatial") # Make sure the spatial extension is checked out
arcpy.env.overwriteOutput=True # Allows us to run the script repeatedly without deleting the intermdiate files

# Create a DEM with sinks filled
FilledRaster=arcpy.sa.Fill(ProcessingFolder+"DemClip3.img")
FilledRaster.save(ProcessingFolder+"FilledRaster.img")

Warning, do not use a large raster for this or you will never finish the assignment. Use a tiny raster (<1 meg) to get started and then test the code with a medium sized raster (<100 meg).

2. Processing Vectors

Create a Python script that will take two shapefiles with polygons and:

• Buffer them to X map units (make this a constant at the top of the file)
• Find their intersection (clip)
• Find their union
• At least two more functions

3. Functions

Create a function to compute the rasters from the first section and another function to compute the vectors from the second section. Place the function in a module (separate file).

Turn-in:

1. A finished Python script with documentation and exception handling
2. A Python module with the two funtions

Note: Remember to place the overall script in a "try/except" block and fully document both files.