This function, shown in the preceding section, essentially draws the geometry from a single input point and rotation value. It does so by using nine instances of ST_MakeLine. Typically, one might use ST_MakeLine in combination with ST_MakePoint to accomplish this. We bypass this need by having the function consume a point geometry as an input. We can, therefore, use ST_Translate to move this point geometry to the endpoints of the lines of interest in order to construct our lines with ST_MakeLine.
One final step, of course, is to test the use of our new geometry constructing function:
CREATE TABLE chp04.tsr_grid AS -- embed inside the function SELECT chp04.create_grid(ST_SetSRID(ST_MakePoint(0,0), 3734), 0) AS the_geom UNION ...
