ASCII Grid files
For most of this chapter we'll use ASCII Grid files or ASCIIGRID . These files are a type of raster data usually associated with elevation data. This grid format stores data as text in equally sized square rows and columns with a simple header. Each cell in a row/column stores a single numeric value, which can represent some feature of terrain, such as elevation, slope, or flow direction. The simplicity makes it an easy-to-use, platform independent raster format. This format is described in the ASCII GRIDS section in Chapter 2, Geospatial Data.
Throughout the book we've relied on GDAL and to some extent PIL to read and write geospatial raster data including the gdalnumeric module to load raster data into NumPy arrays. But ASCIIGRID allows us to read and write rasters using only Python or even NumPy.
Tip
As a reminder, some elevation data sets use image formats to store elevation data. Most image formats only support 8-bit values ranging between 0-255; however, some formats...
