[postgis-users] problem to transform coordinates
Guido Lemoine
guido.lemoine at jrc.it
Mon Aug 4 08:32:16 PDT 2008
Looks like you're mapping around the South Pole. The coordination
transform to 4326 there is going to be very inaccurate (question of the
week: what is the lat lon coordinate of the South Pole itself?)
http://www.uwgb.edu/DutchS/FieldMethods/UTMSystem.htm
suggest you should use "Polar Stereographic" rather than UTM in polar
regions (EPSG=32761 for the South Pole). But this may be small comfort
to you.
GL
Felipe Fedel Pinto wrote:
> SELECT ST_AsText(coord_22523)
> FROM coordsformiga limit 2;
> return:
> st_astext
> -------------------------
> POINT(7650.676 500.29)
> POINT(7624.401 592.751)
> (2 rows)
>
>
>
> SELECT ST_AsText(ST_Transform(coord_
>
> 22523, 4326))
> FROM coordsformiga limit 2;
>
> return:
> st_astext
> -------------------------------------------
> POINT(140.139757378998 -89.9975973774248)
> POINT(140.139757378998 -89.9975973774248)
> (2 rows)
>
>
> SELECT postgis_full_version();
>
> postgis_full_version
> ----------------------------------------------------------------------------------
> POSTGIS="1.3.3" GEOS="3.0.0-CAPI-1.4.1" PROJ="Rel. 4.6.0, 21 Dec
> 2007" USE_STATS
> (1 row)
>
>
>
>
> On Mon, Aug 4, 2008 at 10:20 AM, Obe, Regina
> <robe.dnd at cityofboston.gov <mailto:robe.dnd at cityofboston.gov>> wrote:
>
> Felipe Fedel,
>
> Can you send a sample of your data - results of the 2 queries below
>
> SELECT ST_AsText(coord_22523)
> FROM coordsformiga limit 2;
>
> -- and result you get when you do
> SELECT ST_AsText(ST_Transform(coord_22523, 4326))
> FROM coordsformiga limit 2;
>
> Also what does
>
> SELECT postgis_full_version();
>
> give
>
> Only thought I have that could be wrong is your coordinates are not
> really 22523 or there is a problem with your proj 4 install. The above
> queries should pinpoint that.
>
> Hope that helps,
> Regina
>
> ________________________________
>
> From: postgis-users-bounces at postgis.refractions.net
> <mailto:postgis-users-bounces at postgis.refractions.net>
> [mailto:postgis-users-bounces at postgis.refractions.net
> <mailto:postgis-users-bounces at postgis.refractions.net>] On Behalf Of
> Felipe Fedel Pinto
> Sent: Monday, August 04, 2008 9:27 AM
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] problem to transform coordinates
>
>
> it also happens when I use ST_Transform and return the same thing from
> SELECT proj4text FROM spatial_ref_sys WHERE srid = 22523;
>
>
> Do you have another idea??
>
> Thanks!!!!
>
> Felipe Fedel
>
> On Thu, Jul 31, 2008 at 1:13 AM, Paragon Corporation <lr at pcorp.us
> <mailto:lr at pcorp.us>>
> wrote:
>
>
> Maybe there is something wrong with your entry in the
> spatial_ref_sys table for that SRID. Also provide two sample 22523
> points and what the ST_Transform looks like.
>
> Also please use ST_Transform if you are using a PostGIS install
> > 1.2
>
> What does
>
> SELECT proj4text
> FROM spatial_ref_sys
> WHERE srid = 22523
>
> give you?
>
> Mine gives
> +proj=utm +zone=23 +south +ellps=intl
> +towgs84=-206,172,-6,0,0,0,0 +units=m +no_defs
>
> Hope that helps,
> Regina
>
> ________________________________
>
> From: postgis-users-bounces at postgis.refractions.net
> <mailto:postgis-users-bounces at postgis.refractions.net>
> [mailto:postgis-users-bounces at postgis.refractions.net
> <mailto:postgis-users-bounces at postgis.refractions.net>] On Behalf Of
> Felipe Fedel Pinto
> Sent: Wednesday, July 30, 2008 7:26 PM
> To: postgis-users at postgis.refractions.net
> <mailto:postgis-users at postgis.refractions.net>
> Subject: [postgis-users] problem to transform coordinates
>
>
> To transform coordinates in PostGis I use the followed
> function:
>
> UPDATE <table> SET <new_geometry_column> =
> transform(<original_geometry_column>,<new_SRID>);
>
> I have been having a weird problem when I try to transform
> coordinates that are in a SRID=22523.
> Ex: I have to transform them to a SRID=4326
>
> UPDATE coordsformiga SET coord_4326 =
> transform(coord_22523,4326);
>
> where coordsformiga is the table,
> coord_22523 is the original geometry column with the
> coordinates in a SRID=22523
> coord_4326 I'd be the geometry column with the
> coordinates transformed in a SRID=4326
>
> the problem is:
> After the function, in the geometry column (coord_4326), all of
> the 97 coordinates have the same values.
> But it's happening only with a SRID=22523.
>
> Anybody knows what is happening??
>
> thanks
>
>
>
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Guido Lemoine
Joint Research Centre, European Commission
Institute for the Protection and Security of the Citizen (IPSC)
Support to External Security
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Tel. +39 0332 786239 (direct line) Fax. +39 0332 785154
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