[postgis-users] unit

[Gilbert, Antoine]

I am aware of this

I was just hoping that I could have access to some functions allowing me
to do that kind of calculation easily.

I'm used to MapXTreme Java, when you specify you are using for example
an oracle spatial table as a layer, whatever the srid you told to
MapXTreme, you have functions to extract distance between 2 points in
the unit you want. I was wondering if I could do that given postgis.jar
and the postgis SQL functions. 

Antoine


-----Original Message-----
From: David Bitner [mailto:osgis.lists at gmail.com] 
Sent: January 24, 2006 9:42 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] unit

Yes, for geographic coordinates (latitude/longitude)
distance(geometry) does not really mean anything useful at all.  Think
about what one degree along the equator vs. one degree near the poles.
 Using cartesian math, each distance is the same when in reality they
are very different.  For angular coordinates, you need to use the
angular measurements distance_spheroid and distance_sphere.

On 1/24/06, Markus Schaber <schabi at logix-tt.com> wrote:
> Hi, Gilbert,
>
> Gilbert, Antoine wrote:
>
> > When you are using functions like Distance(geometry, geometry),
withinh
> > SQL queries, does it exists an easy way to tell the system I want
> > kilometer units ?
>
> If your coordinates are in lat/long, than have a look at
> distance_spheroid and distance_sphere, they give the distance in
meters.
>
> Markus
>
> --
> Markus Schaber | Logical Tracking&Tracing International AG
> Dipl. Inf.     | Software Development GIS
>
> Fight against software patents in EU! www.ffii.org
www.nosoftwarepatents.org
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