Re: PostGIS

On Thu, Oct 19, 2006 at 09:31:40PM +0530, Sandeep Kumar Jakkaraju wrote:
> I use postgis to wipe my ASS ...
> no good documentation ...

If you find the documentation lacking then please consider posting
to postgis-users with suggestions for improving it.  Even better,
submit a patch :-)

> in what units is the result of distance(geometry,geometry)..

http://postgis.refractions.net/docs/ch06.html#id2526205

"Return the cartesian distance between two geometries in projected units."

If the geometries are in degrees then distance() returns degrees;
if they're in meters then distance() returns meters; if they're in
cubits then distance() returns cubits.

> what is distance_sphere(geometry,geometry)..

http://postgis.refractions.net/docs/ch06.html#id2528534

"Returns linear distance in meters between two lat/lon points."

> when u give same geometry as both parameters it gives a non-zero
> value ....

test=> SELECT distance(GeomFromText('POINT(12 34)'), GeomFromText('POINT(12 34)'));
 distance
----------
        0
(1 row)

test=> SELECT distance_sphere(GeomFromText('POINT(12 34)'), GeomFromText('POINT(12 34)'));
 distance_sphere
-----------------
               0
(1 row)

If you're getting unexpected behavior then please post a test case
to postgis-users.

--
Michael Fuhr