Module 9 - Working with Rasters

In Programming this week the focus was solely on working with rasters and the Spatial Analyst module available in arcpy (arcpy.sa). For the lab this week the task was to write a script to find areas that met certain criteria in two separate rasters and combine those areas in to one raster showing only two values, areas meeting all criteria and other areas. As I wrote that last statement it seemed like a very easy, but possibly time consuming, task to complete since I've done done this a few times in my Applications class this semester just using the tools in ArcToolbox. The challenging and time saving part to that statement is all of the work was done with a Python script and barely touched ArcMap to complete all of it. One of the most important parts of working with rasters in a spatial analyst sense is having the license for the Spatial Analyst Extension and having the extension enabled in ArcMap. Without those two things, all of the raster manipulating I did this week would not have been possible.

As for the lab, it started with working with a landcover raster. For this raster I selected all three categories of forests in teh landcover types and used the RemapValue to list them along with the new values I wanted to give them. Then I used the Reclassify tool to reclassify the landcover raster based on those new values. The second raster I worked with was an elevation raster. I used the Slope and Aspect tools to create two temporary rasters based on the original elevation raster. These temporary rasters were used to create four more temporary rasters marking the high and low limits for the slope and aspect criteria. Using map algebra I combined the high and low limits as well as the reclassified forest raster with the "&" (and) character to create the final raster shown below. Finally I used the save method to permanently save only this last file. The final raster contains only two values to identify areas that do or do not meet all of the required criteria.

Raster showing areas meeting slope, aspect, and landcover criteria