Is it Lon/Lat or Lat/Lon?
In web mapping APIs like Google Maps, spatial coordinates are often in order of latitude then longitude.
In spatial databases like PostGIS and SQL Server, spatial coordinates are in longitude and then latitude. Mixing the two up can lead to questions like “why is this European city showing up in Africa on my map?”
If you accidentally loaded data in latitude/longitude order, you can easily fix the mistake by using the ST_FlipCoordinates function.
An example use for geometry:
ALTER TABLE sometable ALTER COLUMN geom TYPE geometry(LineString,4326) USING ST_FlipCoordinates(geom);
ALTER TABLE sometable ALTER COLUMN geog TYPE geography(LineString,4326) USING geography(ST_FlipCoordinates(geometry(geom)));