R: [postgis-users] precision of GeomFromTex, Transform and text functions

[P.Rizzi Ag.Mobilità Ambiente]

Probably it does not matter to you in this case,
but EPSG:26591 has been deprecated in favour of EPSG:3003.
There is an error (can't remember what) in 26591.

Bye
Paolo Rizzi


> -----Messaggio originale-----
> Da: postgis-users-bounces at postgis.refractions.net
> [mailto:postgis-users-bounces at postgis.refractions.net]Per conto di
> Ludovico Bianchini
> Inviato: lunedì 3 settembre 2007 21.39
> A: postgis-users at postgis.refractions.net
> Oggetto: [postgis-users] precision of GeomFromTex,Transform and text
> functions
> 
> 
> Hi all,
> 
> I'm using this postgis function:
> - GeomFromText(text, int4) to create a geometry value
> in 4326 spatial_ref_sys
> - Transform(geometry, int4) to convert a geometry from
> 4326 to 26591 when I'm inserting a record and to
> convert 26591 to 4326 when I'm selecting records
> - text(geometry) to convert the geometry column in a
> human-readable string
> 
> The problem is that the operations are not precise:
> the value I obtain via text(transorm(geom_column,
> 4326)) is different from what I inserted via 
> Transform(GeomFromText('POINT(' || $10 || ')', 4326),
> 26591).
> 
> Here an example (lon-lat values separated by a space):
> Insert:37.13953463591601 45.66405322544534
> Select:37.1321614399253 45.6647733181425
> 
> Insert:37.1321614399253 45.6647733181425
> Read:37.1248077366115 45.6654912656918
> 
> Insert:37.1248077366115 45.6654912656918
> Read:37.1174734269995 45.6662070796171
> 
> Is this a 'normal' behaviour?
> Am I omitting anything?
> 
> Thanks in advance for any help!!
> 
> Bye,
> Ludovico 
> 
> 
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