Comparing Map Algebra between ArcGIS 9.x and 10

Map Algebra in ArcGIS 10 has the same characteristics that you are already familiar with from previous releases. Spatial Analyst tools and operators are still accessible through a powerful algebraic language, but in ArcGIS 10, Map Algebra is now also integrated within Python. In addition to all Spatial Analyst functionality, you now have access to all geoprocessing tools and Python functionality (including third-party Python utilities) to model simple to complex phenomena.

In ArcGIS 9.x, Map Algebra was accessed through the Raster Calculator, the Single Output Map Algebra (SOMA) tool, or the Multiple Output Map Algebra (MOMA) tool. In ArcGIS 10, Map Algebra is accessed through the Raster Calculator tool, the Python window, or any Python integrated development environment (IDE).

In ArcGIS 10, the Raster Calculator tool can be used to implement simple as well as complex algebraic Map Algebra statements. The user interface of the tool retains the button calculator of the Raster Calculator that was previously accessed through the Spatial Analyst toolbar. The new Raster Calculator tool, like all geoprocessing tools, can be used in ModelBuilder similarly to SOMA in prior releases.

In ArcGIS 10, the Python window can be used to execute single or multiline Map Algebra expressions as was the case with the 9.x Raster Calculator. In the Python window, you have access to the same functionality as the Raster Calculator and more. The Python window does not have the same user interface tools as Raster Calculator but provides other benefits such as line autocompletion and intelligent drop-down lists to help you create valid expressions. For more complex workflows using Map Algebra it is recommended that you write a stand-alone script using a Python IDE.

The Single Output Map Algebra and Multiple Output Map Algebra tools are not available in the Spatial Analyst toolbox. However, existing SOMA and MOMA tools in geoprocessing models and scripts are still supported and will continue to work. While working in ArcGIS 10, it is recommended that you use the new Map Algebra environment to take advantage of the many enhancements.