[postgis-users] Spheroid Question

[Markus Schaber]

Hi, Stephen,

Stephen Woodbridge wrote:

>>> the_geom && expand(setSRID(makepoint(-72.607912,
>>> 42.058052),4326),0.179664)  AND
>> [Meters per degree]
> You are correct that degrees per meter increases, but we are concerned
> with meters per degree in this example and being the inverse they
> decrease. So by using the value at the equator, we over sample as we
> move toward the poles which is ok, unless it creates a performance
> problem in which case you will have to expand the bbox x and y as you
> suggest.

AFAICS, you give an degree value 0.179664 to expand in your example, and
this makes the bbox too narrow when going to the poles.

Markus