As you've already seen, the
coordinates column from the
sf_sights table contains a long series of characters that are hardly understandable to humans. As you may remember from Part 2 this is an internal format understood by PostGIS. Luckily, we can make it understandable with the
ST_AsText function, which allows us to change the format to Well-Known Text:
The result is quite different than before. Now, in each cell of the
coordinates column we have one of three words: point, linestring, or polygon, followed by the list of coordinates in parentheses. Each word signifies a different subtype or simple type of the geometry in question. In this part of the course we will focus on explaining the purpose and usage of each of these subtypes.