This chapter describes the raster algebra language (PL/SQL and algebraic expressions) and related raster operations, including conditional queries, cell value-based updates or edits, mathematical operations, classify, on-the-fly statistical analysis, logical operations, and their applications in cartographic modeling.

It contains the following major sections.

• Raster Algebra Language
  Raster algebra is commonly used in raster data analysis and GIS modeling. In GeoRaster, raster algebra is supported by the GeoRaster raster algebra language.
• Cell Value-Based Conditional Queries
  Using cell-based conditional queries, you can generate a new GeoRaster object based on a specified condition.
• Cell Value-Based Conditional Updates (Edits)
  You can update raster cell values based on conditions.
• Mathematical Operations
  A major use of raster algebra is to apply mathematical models to raster layers from different sources.
• Classification Operations
  Classification (segmentation) operations can be applied on source GeoRaster objects to generate new objects.
• Statistical Operations
  To apply statistical operations on one or more layers, which are from one or more GeoRaster objects, the following types of operations are available.
• Logical Operations
  A major use of raster algebra is to apply logical models to raster layers from different sources; that is, you can apply logical operations on one or more layers, from one or more GeoRaster objects, to generate a new GeoRaster object.
• Raster Data Scaling and Offsetting
  You can perform raster data scaling and offsetting operations.
• Raster Data Casting
  Raster data casting maps cell values from one data type to another.
• Cartographic Modeling
  Raster algebra is widely used in cartographic modeling and is considered an essential component of GIS systems. Using the PL/SQL and the raster algebra expressions and functions, you can conduct cartographic modeling over a large number of rasters and images of virtually unlimited size.
• Terrain Modeling and Analysis
  You can use the data from input GeoRaster objects to perform terrain modeling and analysis.