Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

Rasters: Input, Computation, and Output

It would be less than candid to suggest that using spatial analyst for analysis is anything but complex. A large number of ideas, approaches, techniques, and data types are in play here. Let’s return to the most fundamental level of computer operation. A computer reads bits, stirs bits, and writes bits. That is, there is input, computation, and output.

For any operation in SA, the inputs can be

• One or more rasters
• One or more feature layers
• Parameters specified at the time of the operation
• Settings provided by a spatial analyst environment

For any operation in spatial analyst the outputs can be

• A raster
• A feature layer
• Statistics

You have a good appreciation for feature layers by this time. You are learning about rasters—what a raster is and some of its characteristics. Parameters and statistics have been part of many of the operations you have applied to vector data sets. Environment settings will be discussed in the Step-by-Step section of this chapter.