I put these docs together in an effort to help my colleagues at the City of Boston get acquainted with PostGIS. You can find Part 1 here.
This section walks through adding a geometry column to a dataset, dealing with projection systems, and getting x/y values from a geometry column.
Adding and Populating a Geometry Column
PostGIS stores a table’s spatial information in geometry columns. Usually these columns have the word “geom” floating around in their name. If you select * on a table with a geometry column, the geom column will look like a long series of nonsense.
Frequently, long/lat values get stored in columns in a database or spreadsheet. To make these into a geometry column that PostGIS understands, we: