[postgis-users] spheroid bounding box calculation

[Paul Ramsey]

Just isn't such a thing, is all. I guess an st_expand_sphere() would
be what you wanted, but does not exist. Hopefully GEOGRAPHY will
retire all these requirements once and for all :)

P

On Thu, Jul 23, 2009 at 8:49 AM, Jeff Davis<pgsql at j-davis.com> wrote:
> On Thu, 2009-07-23 at 07:06 -0400, Stephen Frost wrote:
>> Why do you care about it being in meters..?
>
> Well, all I care about is that it's in some kind of linear length units.
> Queries might take the form of "what else is within 3 miles of this
> lat/lon point?".
>
>> Just make sure that
>> st_expand will grow it large enough to be within the distance limit
>> you're looking for everywhere, and then convert to UTM for the actual
>> source point and use distance() there to further refine the search.
>>
>> Use the bounding box to narrow the search, don't try to use it *as* your
>> search criteria.
>>
>
> That's what I'm trying to do. But how do I ensure that the bounding box
> is big enough to account for points near the poles, but not too big for
> points near the equator?
>
> I suppose it's not really necessary for it to be accurate near the
> poles, but I'm curious why there's not a function that works everywhere.
>
> Regards,
>        Jeff Davis
>
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