Summary
In this chapter, we prepared data so that it could be imported and analyzed. You were introduced to new spatial functions so that you can estimate areas of polygons and define relationships between and within polygons. You even learned how to create your own functions. These are handy to know especially when you might return to datasets that are frequently updated.
In the next chapter, we will expand on building SQL queries in the QGIS graphical query builder that you were introduced to when filtering the roads data. SQL is indeed a powerful tool for creating efficient workflows and optimizing the power of working with GIS tools such as QGIS.
