In this chapter, we looked more closely at the data used for geospatial analysis. We saw why having high-quality geospatial data is important, the various types of geospatial data you are likely to encounter, and the major websites which provide quality geospatial data for free. We then looked at how to read and write both vector and raster format geospatial data using GDAL and OGR, and learned about spatial reference systems. Finally, we looked at the ways in which geospatial data can become invalid, and how to fix it.

In the next chapter, we will look at spatial databases and how they can be used as a powerful tool for geospatial analysis.