[postgis-users] Simple question: How to get projected distance?

strk at refractions.net strk at refractions.net
Sat Aug 13 01:23:03 PDT 2005

On Sat, Aug 13, 2005 at 04:14:46AM -0400, Lance Arlaus wrote:
> Paul-
> Sounds like you're in corporate land with deep pockets :)  Thanks for the
> suggestion though - I guess I originally assumed that's what I'd be getting
> with PostGIS :(
> Know of any ready made CONUS projections and their accuracy?  I'd like to
> research Lambert parameterizations (I pulled up a paper or two), but right
> now I've gotta get a job to get done and this is just one small piece.
> I know this is another discussion, but my original first thought on solving
> this mapping problem was to derive, either numerically or in closed form, a
> formula for dx/dlong and integrate it to find relative displacement values.
> For example, a 10 degree shift in longitude at 50 degrees latitude may be
> equal to 100km.  Of course, this is probably what some of these
> parameterizations are accomplishing, but I just haven't looked into it
> enough.
> Barring a more elegant solution (a decent CONUS projection), I guess I'll be
> using the WGS84 UTM round trip.  Additional thoughts and suggestions are
> certainly welcome.

Does spatial_ref_sys already contain all the utm cells ?
I'd make a plpgsql wrapper (if I were you I mean ;)
looking for (or adding) entries into spatial_ref_sys and
calling the transform/buffer/transform loop.

What about a getUTMproj(zone, fuse) returning a SRID
either found or added ?


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