Обсуждение: ST_Distance Issue

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ST_Distance Issue

От
Archana Sachin Ghag
Дата:
I am calculating distance from my current location with all available regio=
ns(polygons) in my table.
I am using ST_Distance method for this.
My regions are stored with SRID =3D 900913.

Distance for point in Europe from USA region is coming as 122.78.
How come this possible. These regions are so far.

Here is my query. Can you please suggest me how can I get actual distance i=
n meters here.

SELECT distance
(st_geomfromtext('point(-123.574219125 47.8131546948944 0)', 900913),
st_geomfromtext('LINESTRING(-0.791015625 48.4874864798841,9.4921875 54.5975=
278521139,27.59765625 55.3541353102106,36.38671875 48.3124279040718,22.3242=
1875 40.3465441211801,5.888671875 43.8662180065564,-0.791015625 48.48748647=
98841)', 900913)
)

Query returns 122.785055218779

What is significance of SRID here. Am I missing something?
Which SRID should we use for general purpose.

Thanks,
Archana Ghag
----------------------------------------------------
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Tel:  2022978913(VOIP) : +91-9850872739 (Mobile)
email: archana_ghag@infosys.com<mailto:archana_ghag@infosys.com>


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Re: ST_Distance Issue

От
Robert Haas
Дата:
On Thu, Nov 17, 2011 at 4:29 AM, Archana Sachin Ghag <
Archana_Ghag@infosys.com> wrote:

> I am calculating distance from my current location with all available
> regions(polygons) in my table.****
>
> I am using ST_Distance method for this.****
>
> My regions are stored with SRID = 900913.****
>
> ** **
>
> Distance for point in Europe from USA region is coming as 122.78.****
>
> How come this possible. These regions are so far.****
>
> ** **
>
> Here is my query. Can you please suggest me how can I get actual distance
> in meters here.****
>
> ** **
>
> SELECT distance****
>
> (st_geomfromtext('point(-123.574219125 47.8131546948944 0)', 900913),****
>
> st_geomfromtext('LINESTRING(-0.791015625 48.4874864798841,9.4921875
> 54.5975278521139,27.59765625 55.3541353102106,36.38671875
> 48.3124279040718,22.32421875 40.3465441211801,5.888671875
> 43.8662180065564,-0.791015625 48.4874864798841)', 900913)****
>
> )****
>
> ** **
>
> Query returns 122.785055218779****
>
> ** **
>
> What is significance of SRID here. Am I missing something?****
>
> Which SRID should we use for general purpose.
>

This mailing list is for bugs in PostgreSQL; it sounds like you have a user
question about PostGIS.

I think this might be the right place:

http://postgis.refractions.net/mailman/listinfo/postgis-users

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company