How to measure width in KMs with geos

Question

I've got a bounding box, and I want to adjust it so it's not less than, say, 2km across. I get the bounding box from google's geolocate service, and then I search for stuff that's inside that in my database, but I want to make sure I don't test against anything smaller than 1 or 2km across.. I'd like to get the area, measure the with, height, and expand pivoting on the center in case it's needed.

I already have all the SRID and stuff right.

Thanks

Answer 1

The answer to this depends on the SRID. You call expand which gets a unitless float as a parameter, and the units on that depend on the units with which the SRID is defined.