To end this chapter with a bang, here is the most complicated conversion we have seen so far and the most fun as well. Input is an elevation dataset that's stored in ASCII format, more specifically, Arc/Info ASCII Grid, for short with the AAIGrid with the (.asc) file ending. Our output is a heightmap image (http://en.wikipedia.org/wiki/Heightmap). A heightmap image is an image that stores height elevation as a pixel value. A heightmap is also simply known as a digital elevation model (DEM). The benefit of using an image to store elevation data is that it is web compatible and we can use this in a 3D visualization with threejs, for example, as shown in Chapter 10, Visualizing Your Analysis.

We need to be careful with regard to the output image format because simply storing an 8-bit image limits us to only storing 0 to 255 height values, which is typically not enough. The output image should store a minimum of 16-bits, giving us a range from...