Working with Rasters in Python

The corollary to working with feature geometry in vector datasets could be described as the use of the Spatial Analyst extension to access the arcpy.sa module, which allows one to work with raster datasets in Python.  This module comes complete with its own tools, functions and idiosyncrasies, which were the focus of this week's Python script.

     
Reclassification of raster data can be a cumbersome process using the Spatial Analyst tools available in ArcMap, particularly when the required result is a classification raster involving the combination of several re-classified inputs.  This task is relatively simple by comparison within a Python script though, which takes each intermediary input as a temporary dataset, and saves only user specified results.  The Python script also completes with a few short lines of code what would otherwise be completed through the creation of multiple separate raster datasets with the tools available within the Spatial Analysis Toolbox.  The efficiency of the code's ability to reclassify, and then combine to create a final output of areas containing specified characteristics, various raster data cannot be overstated.  The above image represents an area with characteristics meeting all of a set of some specified conditions- namely that the land has a particular type of landcover, and a specified range of slope and aspect.  Two input raster datasets were employed in its creation- one with landcover types, and another with elevation.  The elevation data was used to create datasets with slope and aspect characteristic attributes, and the landcover was reclassified to contain only those areas categorized as "forested."  The resulting output is the combination of the suitable areas within each of the inputs, and represents the land within the specified areal extent that meets the landcover, slope and aspect suitability requirements.