Accessing ASCII Grid files

For most of this chapter, we’ll use ASCII Grid files, or ASCIIGRID. These files are a type of raster data that’s usually associated with elevation data. This grid format stores data as text in equal-sized square rows and columns with a simple header. Each cell in a row/column stores a single integer used to represent a given feature of the terrain, such as the elevation, slope, or flow direction. The simplicity makes it an easy-to-use and platform-independent raster format. This format was described in the ASCII grids section of Chapter 2, Learning about Geospatial Data.

Throughout this book, we’ve relied on GDAL, and to some extent, even PIL, to read and write geospatial raster data, including the gdal_array module, so that we can load raster data into NumPy arrays. ASCII Grid allows us to read and write rasters using only Python or even NumPy because it is simple plain text.

Using simple elevation formats

As a reminder, some...