[postgis-users] Fw: Re: Convert from 3067 to 2393

[Pena Kupen]

Ralf,

On our spatial_ref_sys at 2393 there is proj4text as
+proj=tmerc +lat_0=0 +lon_0=27 +k=1.000000 +x_0=3500000 +y_0=0 +ellps=intl +units=m +no_defs 

It seems that +towgs4 is missing? If I change this, it it safe?

Do you mean like this?
select x(ST_Transform(ST_Transform( tbl.p, 4326),2393)), y(ST_Transform(ST_Transform( tbl.p, 4326),2393)) from
(select GeomFromText('POINT(108043 6683685)',3067) as p) as tbl

Result is same as before as:
3107866.533 6686516.654

--
Pena

Ralf Suhr [Ralf.Suhr at itc-halle.de] kirjoitti: 
> Hi Pena,
> 
> first verify EPSG:2393 is set with correct towgs84 parameters in 
> spatial_ref_sys (http://spatialreference.org/ref/epsg/2393/proj4/).
> 
> Because the destination EPSG is not based on WGS84 ellipsoid you have to 
> transform twice: ST_Transform( ST_Transform( POINT_FROM_3067, 4326), 2393)
> 
> Gr
> Ralf
> 
> Am Freitag 04 März 2011, 11:53:44 schrieb Pena Kupen:
> > Hello all,
> > 
> > I try to do some conversion between different coordinates (3067 to 2393 )
> > without saving them to database. My sql is following:
> > select x(ST_Transform(tbl.p,2393)), y(ST_Transform(tbl.p,2393)) from
> > (select GeomFromText('POINT(108043 6683685)',3067) as p) as tbl
> > 
> > result:
> > 3107866.533 6686516.654
> > 
> > Correct one is:
> > 3108053.305 6686493.081
> > 
> > location is about 200m too much on west.
> > 
> > Any ideas?
> > 


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