ArcGIS Spatial Analyst provides a broad range of powerful modeling and analysis features that allow you to quickly derive the information you need from your GIS data. You can perform this analysis in a variety of ways.
There are several distance mapping tools for measuring both straight-line (Euclidean) distance and distance measured in terms of other factors such as the cost to travel over the landscape.
Neighborhood functions create output values for each cell location based on the value for that location and the values identified in a specified neighborhood.
Zonal functions take a value raster as input and calculate for each cell some function or statistic using the value for that cell and all cells belonging to the same zone.
The Raster Generalization tools are used to either clean up small erroneous pixels in the raster or to generalize the data to remove or smooth out unnecessary detail.
ArcGIS Spatial Analyst enables you to create custom tools and models for spatial analysis and incorporate these tools directly into the ArcGIS interface.
ArcGIS Spatial Analyst is part of ArcGIS Engine and can, therefore, be used as part of a distributed GIS analysis system in a client/server environment or for remote, Internet-based spatial modeling through thick or thin clients.