Chapter 12. Raster processing

 

This chapter covers

  • Loading raster data
  • Spatial aggregate raster functions
  • Using geometries to clip rasters
  • Accessing pixel values and isolating bands
  • Retiling rasters
  • Raster statistical functions
  • Map algebra functions

In this chapter, we’ll focus on the use of raster aggregate functions, functions to manipulate rasters down to the pixel level, and functions for deriving additional rasters and geometries. We’ll also demonstrate built-in summary statistics functions that you can use to learn more about the distribution of pixel values. You’ll see in the examples that we consistently use geometry to isolate pixel values of interest. Being able to use geometry and raster in tandem is a powerful aspect of PostGIS.

For this chapter, our discussion presumes that you have PostGIS 2.1 or higher. Although we do highlight salient changes between 2.0 and 2.1, we strongly encourage you to upgrade to PostGIS 2.1 (if you haven’t already done so) so you can take advantage of the latest functions for rasters. As an added bonus, you’ll luxuriate in significant speed gains for some of the most taxing functions.

12.1. Loading and preparing data

12.2. Forming larger rasters using spatial aggregate functions

12.3. Working with bands

12.4. Tiling rasters

12.5. Raster and geometry intersections

12.6. Raster statistics

12.7. Map algebra

12.8. Summary