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

2007-09-05 Thread Frank Koormann 
* Ludovico Bianchini <[EMAIL PROTECTED]> [070904 16:03]:
> I have this question: is there a parameter simmetric
> to TOWGS? If so the project library shall use FROMWGS
> to convert from the gps system and TOWGS to convert to
> the gps system.
> Sorry if the question is stupid, but I don't
> understand how to solve this problem (to convert gps
> (SRID=4326) to West Gauss Boaga Italy Rome Monte Mario
> (SRID=26591 or 3003).

The towgs84 (note the 84!) decribes a correction performed by a
bijective matrix multiplication. Hence the inverse can be used
for the other direction "from" wgs. Proj4 does this automatically.

Regards,

Frank

-- 
Frank Koormann  |  ++49-541-335 08 30  |  http://www.intevation.de/
Intevation GmbH, Georgstr. 4, 49074 Osnabrück, DE | AG Osnabrück, HR B 18998
Geschäftsführer: Frank Koormann, Bernhard Reiter, Dr. Jan-Oliver Wagner
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R: R: R: [postgis-users] precision of GeomFromTex, Transform and text functions

2007-09-04 Thread P . Rizzi Ag . Mobilità Ambiente 
I'm happy to hear this!!!
Please remember to use 3003 intead of 26591.
If I remember well there was some kind of offset error using the former.
It has been deprecated by EPSG on 16 Jan 2003 with this motivation:
"Associated with incorrect datum resulting in map projection longitude being 
incompatible with prime meridian."

In fact 26591 uses this prime meridian:
PRIMEM["Rome",12.452333,AUTHORITY["EPSG","8906"]]

while 3003 uses this one:
PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]]

The same applies for 3004 vs 26592.

Bye
Paolo Rizzi


> -Messaggio originale-
> Da: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] conto di
> Ludovico Bianchini
> Inviato: martedì 4 settembre 2007 17.51
> A: PostGIS Users Discussion
> Oggetto: Re: R: R: [postgis-users] precision of GeomFromTex,Transform
> and text functions
> 
> 
> Hi,
> you have centered the problem.
> With lon-lat couples situated in Italy it's work.
> 
> The wrong longitude (I was convinced that 37 was in
> Italy) was born using java mapscript (a mapserver
> related component) to calculate a test value,
> converting the coords of a point in Treviso:
> 
> x = 1752000f;
> y = 5062000f;
> point.setX(x);
> point.setY(y);
> point.project(new projectionObj("init=EPSG:26591"),
> new projectionObj("init=EPSG:4326"));
> point.toString();//37.13953463591601 45.66405322544534
> 
> So I've now understood that the problem is not in
> postgis but in the epsg values that java mapscript
> uses in conversions. I'll search in this direction.
> 
> Thank you very much for your helpful replies!!
> 
> 
> --- P.Rizzi Ag.Mobilità Ambiente
> <[EMAIL PROTECTED]> ha scritto:
> 
> > There's no FROMWGS parameter, TOWGS is all that's
> > needed,
> > as far as I know.
> > Problem may be that the coordinates you are using
> > have
> > a longitude (37.) not inside Italy (actually
> > they apper to be 
> > somewhere in southern Russia near the Georgia
> > border).
> > If you do the insert/select using coordinates like:
> > 9.13953463591601 45.66405322544534
> > 
> > it should work as expected.
> > 
> > Bye
> > Paolo Rizzi
> > 
> > 
> > > -Messaggio originale-
> > > Da: [EMAIL PROTECTED]
> > >
> >
> [mailto:[EMAIL PROTECTED]
> > conto di
> > > Ludovico Bianchini
> > > Inviato: martedì 4 settembre 2007 16.02
> > > A: PostGIS Users Discussion
> > > Oggetto: Re: R: [postgis-users] precision of
> > GeomFromTex,Transform and
> > > text functions
> > > 
> > > 
> > > Thanks for the suggestion, actually there were not
> > the
> > > toWGS parameter in spatial_ref_sys table.
> > > 
> > > The situation seems to be a little better (here a
> > > sequence of insert-select:
> > > Insert:37.13953463591601 45.66405322544534
> > > Select:37.1321637582786 45.6647731135686
> > > 
> > > Insert:37.1321637582786 45.6647731135686
> > > Select:37.1248123607135 45.6654908577754
> > > 
> > > Insert:37.1248123607135 45.6654908577754
> > > Select:37.1174803443424 45.6662064695791), but the
> > > error is still too big.
> > > 
> > > I have this question: is there a parameter
> > simmetric
> > > to TOWGS? If so the project library shall use
> > FROMWGS
> > > to convert from the gps system and TOWGS to
> > convert to
> > > the gps system.
> > > Sorry if the question is stupid, but I don't
> > > understand how to solve this problem (to convert
> > gps
> > > (SRID=4326) to West Gauss Boaga Italy Rome Monte
> > Mario
> > > (SRID=26591 or 3003).
> > > 
> > > Any help will be very appreciated!!!
> > > 
> > > Ludovico
> > > 
> > > 
> > > --- P.Rizzi Ag.Mobilità Ambiente
> > > <[EMAIL PROTECTED]> ha scritto:
> > > 
> > > > I forget to mention the fact that inside the
> > PostGIS
> > > > spatial_ref_sys
> > > > table, TOWGS parameters are missing for
> > EPSG:26591
> > > > and for 3003 too.
> > > > So any transform will not be precise in any
> > case.
> > > > To add parameters for EPSG:3003, you can use the
> > > > following SQL
> > > > in any DB that you need to.
> > > > 
> > > > Bye
> > > > Paolo Rizzi
> > > > 
> > > > 
> &g

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

2007-09-04 Thread Ludovico Bianchini 
Hi,
you have centered the problem.
With lon-lat couples situated in Italy it's work.

The wrong longitude (I was convinced that 37 was in
Italy) was born using java mapscript (a mapserver
related component) to calculate a test value,
converting the coords of a point in Treviso:

x = 1752000f;
y = 5062000f;
point.setX(x);
point.setY(y);
point.project(new projectionObj("init=EPSG:26591"),
new projectionObj("init=EPSG:4326"));
point.toString();//37.13953463591601 45.66405322544534

So I've now understood that the problem is not in
postgis but in the epsg values that java mapscript
uses in conversions. I'll search in this direction.

Thank you very much for your helpful replies!!


--- P.Rizzi Ag.Mobilità Ambiente
<[EMAIL PROTECTED]> ha scritto:

> There's no FROMWGS parameter, TOWGS is all that's
> needed,
> as far as I know.
> Problem may be that the coordinates you are using
> have
> a longitude (37.) not inside Italy (actually
> they apper to be 
> somewhere in southern Russia near the Georgia
> border).
> If you do the insert/select using coordinates like:
>   9.13953463591601 45.66405322544534
> 
> it should work as expected.
> 
> Bye
> Paolo Rizzi
> 
> 
> > -Messaggio originale-
> > Da: [EMAIL PROTECTED]
> >
>
[mailto:[EMAIL PROTECTED]
> conto di
> > Ludovico Bianchini
> > Inviato: martedì 4 settembre 2007 16.02
> > A: PostGIS Users Discussion
> > Oggetto: Re: R: [postgis-users] precision of
> GeomFromTex,Transform and
> > text functions
> > 
> > 
> > Thanks for the suggestion, actually there were not
> the
> > toWGS parameter in spatial_ref_sys table.
> > 
> > The situation seems to be a little better (here a
> > sequence of insert-select:
> > Insert:37.13953463591601 45.66405322544534
> > Select:37.1321637582786 45.6647731135686
> > 
> > Insert:37.1321637582786 45.6647731135686
> > Select:37.1248123607135 45.6654908577754
> > 
> > Insert:37.1248123607135 45.6654908577754
> > Select:37.1174803443424 45.6662064695791), but the
> > error is still too big.
> > 
> > I have this question: is there a parameter
> simmetric
> > to TOWGS? If so the project library shall use
> FROMWGS
> > to convert from the gps system and TOWGS to
> convert to
> > the gps system.
> > Sorry if the question is stupid, but I don't
> > understand how to solve this problem (to convert
> gps
> > (SRID=4326) to West Gauss Boaga Italy Rome Monte
> Mario
> > (SRID=26591 or 3003).
> > 
> > Any help will be very appreciated!!!
> > 
> > Ludovico
> > 
> > 
> > --- P.Rizzi Ag.Mobilità Ambiente
> > <[EMAIL PROTECTED]> ha scritto:
> > 
> > > I forget to mention the fact that inside the
> PostGIS
> > > spatial_ref_sys
> > > table, TOWGS parameters are missing for
> EPSG:26591
> > > and for 3003 too.
> > > So any transform will not be precise in any
> case.
> > > To add parameters for EPSG:3003, you can use the
> > > following SQL
> > > in any DB that you need to.
> > > 
> > > Bye
> > > Paolo Rizzi
> > > 
> > > 
> > > ---
> > > --- To add TOWGS parameters, if needed, to:
> > > ---
> > > --- EPSG 3003 : Monte Mario / Italy zone 1
> > > ---
> > > --- If parameters are already present, no change
> > > will take place.
> > > ---
> > > UPDATE "spatial_ref_sys" SET
> > > "srtext"='PROJCS["Monte Mario / Italy zone
> > > 1",GEOGCS["Monte
> > >
> Mario",DATUM["Monte_Mario",SPHEROID["International
> > >
> >
>
1924",6378388,297,AUTHORITY["EPSG","7022"]],TOWGS84[-104.1,-49
> >
>
.1,-9.9,0.971,-2.917,0.714,-11.68],AUTHORITY["EPSG","6265"]],P
> >
>
RIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.
> >
>
01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","
> >
>
4265"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_
> >
>
of_origin",0],PARAMETER["central_meridian",9],PARAMETER["scale
> >
>
_factor",0.9996],PARAMETER["false_easting",150],PARAMETER[
> >
>
"false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]],A
> > UTHORITY["EPSG","3003"]]'
> > > WHERE "s

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

2007-09-04 Thread P . Rizzi Ag . Mobilità Ambiente 
There's no FROMWGS parameter, TOWGS is all that's needed,
as far as I know.
Problem may be that the coordinates you are using have
a longitude (37.) not inside Italy (actually they apper to be 
somewhere in southern Russia near the Georgia border).
If you do the insert/select using coordinates like:
9.13953463591601 45.66405322544534

it should work as expected.

Bye
Paolo Rizzi


> -Messaggio originale-
> Da: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] conto di
> Ludovico Bianchini
> Inviato: martedì 4 settembre 2007 16.02
> A: PostGIS Users Discussion
> Oggetto: Re: R: [postgis-users] precision of GeomFromTex,Transform and
> text functions
> 
> 
> Thanks for the suggestion, actually there were not the
> toWGS parameter in spatial_ref_sys table.
> 
> The situation seems to be a little better (here a
> sequence of insert-select:
> Insert:37.13953463591601 45.66405322544534
> Select:37.1321637582786 45.6647731135686
> 
> Insert:37.1321637582786 45.6647731135686
> Select:37.1248123607135 45.6654908577754
> 
> Insert:37.1248123607135 45.6654908577754
> Select:37.1174803443424 45.6662064695791), but the
> error is still too big.
> 
> I have this question: is there a parameter simmetric
> to TOWGS? If so the project library shall use FROMWGS
> to convert from the gps system and TOWGS to convert to
> the gps system.
> Sorry if the question is stupid, but I don't
> understand how to solve this problem (to convert gps
> (SRID=4326) to West Gauss Boaga Italy Rome Monte Mario
> (SRID=26591 or 3003).
> 
> Any help will be very appreciated!!!
> 
> Ludovico
> 
> 
> --- P.Rizzi Ag.Mobilità Ambiente
> <[EMAIL PROTECTED]> ha scritto:
> 
> > I forget to mention the fact that inside the PostGIS
> > spatial_ref_sys
> > table, TOWGS parameters are missing for EPSG:26591
> > and for 3003 too.
> > So any transform will not be precise in any case.
> > To add parameters for EPSG:3003, you can use the
> > following SQL
> > in any DB that you need to.
> > 
> > Bye
> > Paolo Rizzi
> > 
> > 
> > ---
> > --- To add TOWGS parameters, if needed, to:
> > ---
> > --- EPSG 3003 : Monte Mario / Italy zone 1
> > ---
> > --- If parameters are already present, no change
> > will take place.
> > ---
> > UPDATE "spatial_ref_sys" SET
> > "srtext"='PROJCS["Monte Mario / Italy zone
> > 1",GEOGCS["Monte
> > Mario",DATUM["Monte_Mario",SPHEROID["International
> >
> 1924",6378388,297,AUTHORITY["EPSG","7022"]],TOWGS84[-104.1,-49
> .1,-9.9,0.971,-2.917,0.714,-11.68],AUTHORITY["EPSG","6265"]],P
> RIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.
> 01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","
> 4265"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_
> of_origin",0],PARAMETER["central_meridian",9],PARAMETER["scale
> _factor",0.9996],PARAMETER["false_easting",150],PARAMETER[
> "false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]],A
> UTHORITY["EPSG","3003"]]'
> > WHERE "srid"=3003 AND "auth_name"='EPSG' AND
> > "srtext" NOT LIKE '%TOWGS%';
> > 
> > UPDATE "spatial_ref_sys" SET
> > "proj4text"='+proj=tmerc +lat_0=0 +lon_0=9
> > +k=0.999600 +x_0=150 +y_0=0 +ellps=intl +units=m
> > +no_defs
> >
> +towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68'
> > WHERE "srid"=3003 AND "auth_name"='EPSG' AND
> > "proj4text" NOT LIKE '%towgs%';
> > 
> > 
> > 
> > 
> > > -----Messaggio originale-
> > > Da: [EMAIL PROTECTED]
> > >
> >
> [mailto:[EMAIL PROTECTED]
> > conto di
> > > P.Rizzi Ag.Mobilità Ambiente
> > > Inviato: martedì 4 settembre 2007 11.25
> > > A: PostGIS Users Discussion
> > > Oggetto: R: [postgis-users] precision of 
> > > GeomFromTex,Transform and text
> > > functions
> > > 
> > > 
> > > 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
> > > 
> > > 
> > > > -Mess

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

2007-09-04 Thread Ludovico Bianchini 
Thanks for the suggestion, actually there were not the
toWGS parameter in spatial_ref_sys table.

The situation seems to be a little better (here a
sequence of insert-select:
Insert:37.13953463591601 45.66405322544534
Select:37.1321637582786 45.6647731135686

Insert:37.1321637582786 45.6647731135686
Select:37.1248123607135 45.6654908577754

Insert:37.1248123607135 45.6654908577754
Select:37.1174803443424 45.6662064695791), but the
error is still too big.

I have this question: is there a parameter simmetric
to TOWGS? If so the project library shall use FROMWGS
to convert from the gps system and TOWGS to convert to
the gps system.
Sorry if the question is stupid, but I don't
understand how to solve this problem (to convert gps
(SRID=4326) to West Gauss Boaga Italy Rome Monte Mario
(SRID=26591 or 3003).

Any help will be very appreciated!!!

Ludovico


--- P.Rizzi Ag.Mobilità Ambiente
<[EMAIL PROTECTED]> ha scritto:

> I forget to mention the fact that inside the PostGIS
> spatial_ref_sys
> table, TOWGS parameters are missing for EPSG:26591
> and for 3003 too.
> So any transform will not be precise in any case.
> To add parameters for EPSG:3003, you can use the
> following SQL
> in any DB that you need to.
> 
> Bye
> Paolo Rizzi
> 
> 
> ---
> --- To add TOWGS parameters, if needed, to:
> ---
> --- EPSG 3003 : Monte Mario / Italy zone 1
> ---
> --- If parameters are already present, no change
> will take place.
> ---
> UPDATE "spatial_ref_sys" SET
> "srtext"='PROJCS["Monte Mario / Italy zone
> 1",GEOGCS["Monte
> Mario",DATUM["Monte_Mario",SPHEROID["International
>
1924",6378388,297,AUTHORITY["EPSG","7022"]],TOWGS84[-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68],AUTHORITY["EPSG","6265"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4265"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",9],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",150],PARAMETER["false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AUTHORITY["EPSG","3003"]]'
> WHERE "srid"=3003 AND "auth_name"='EPSG' AND
> "srtext" NOT LIKE '%TOWGS%';
> 
> UPDATE "spatial_ref_sys" SET
> "proj4text"='+proj=tmerc +lat_0=0 +lon_0=9
> +k=0.999600 +x_0=150 +y_0=0 +ellps=intl +units=m
> +no_defs
>
+towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68'
> WHERE "srid"=3003 AND "auth_name"='EPSG' AND
> "proj4text" NOT LIKE '%towgs%';
> 
> 
> 
> 
> > -Messaggio originale-
> > Da: [EMAIL PROTECTED]
> >
>
[mailto:[EMAIL PROTECTED]
> conto di
> > P.Rizzi Ag.Mobilità Ambiente
> > Inviato: martedì 4 settembre 2007 11.25
> > A: PostGIS Users Discussion
> > Oggetto: R: [postgis-users] precision of 
> > GeomFromTex,Transform and text
> > functions
> > 
> > 
> > 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:
> [EMAIL PROTECTED]
> > >
>
[mailto:[EMAIL PROTECTED]
> conto di
> > > Ludovico Bianchini
> > > Inviato: lunedì 3 settembre 2007 21.39
> > > A: postgis-users@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),
> > > 26

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

2007-09-04 Thread P . Rizzi Ag . Mobilità Ambiente 
I forget to mention the fact that inside the PostGIS spatial_ref_sys
table, TOWGS parameters are missing for EPSG:26591 and for 3003 too.
So any transform will not be precise in any case.
To add parameters for EPSG:3003, you can use the following SQL
in any DB that you need to.

Bye
Paolo Rizzi


---
--- To add TOWGS parameters, if needed, to:
---
--- EPSG 3003 : Monte Mario / Italy zone 1
---
--- If parameters are already present, no change will take place.
---
UPDATE "spatial_ref_sys" SET
"srtext"='PROJCS["Monte Mario / Italy zone 1",GEOGCS["Monte 
Mario",DATUM["Monte_Mario",SPHEROID["International 
1924",6378388,297,AUTHORITY["EPSG","7022"]],TOWGS84[-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68],AUTHORITY["EPSG","6265"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4265"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",9],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",150],PARAMETER["false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AUTHORITY["EPSG","3003"]]'
WHERE "srid"=3003 AND "auth_name"='EPSG' AND "srtext" NOT LIKE '%TOWGS%';

UPDATE "spatial_ref_sys" SET
"proj4text"='+proj=tmerc +lat_0=0 +lon_0=9 +k=0.999600 +x_0=150 +y_0=0 
+ellps=intl +units=m +no_defs 
+towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68'
WHERE "srid"=3003 AND "auth_name"='EPSG' AND "proj4text" NOT LIKE '%towgs%';




> -Messaggio originale-
> Da: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] conto di
> P.Rizzi Ag.Mobilità Ambiente
> Inviato: martedì 4 settembre 2007 11.25
> A: PostGIS Users Discussion
> Oggetto: R: [postgis-users] precision of 
> GeomFromTex,Transform and text
> functions
> 
> 
> 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: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] conto di
> > Ludovico Bianchini
> > Inviato: lunedì 3 settembre 2007 21.39
> > A: postgis-users@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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> > 
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R: [postgis-users] precision of GeomFromTex, Transform and text functions

2007-09-04 Thread 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: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] conto di
> Ludovico Bianchini
> Inviato: lunedì 3 settembre 2007 21.39
> A: postgis-users@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 
> 
> 
>   ___ 
> L'email della prossima generazione? Puoi averla con la nuova 
> Yahoo! Mail: http://it.docs.yahoo.com/nowyoucan.html
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[postgis-users] precision of GeomFromTex, Transform and text functions

2007-09-03 Thread Ludovico Bianchini 
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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