[postgis-users] transform() does not do work for NGO1948 zone III-> WGS84 longlat (epsg:27393->epsg:4326)

[Havard Tveite]

It is nice to provide warnings, but for epsg:27393 -> epsg:4326
the following problems persist:

1) Longitude of origin (+lon_0=-10.72291666666667) is ignored
    (as demonstrated by strk's query).
2) No datum shift seems to be performed.

Since the transformation runs smoothly using UMN Mapserver (
with dynamically linked proj - so it should be 4.4.9), there
is probably a problem somewhere.


I have an old PostGIS running (0.8 over 7.4.1 - proj statically
linked "old" version), and for that setup, the transformation
seems to be OK (including datum shift).

select AsText(
transform('SRID=27393;POINT(2836.394208896 185526.991186176)',4326)
);
 >  POINT(10.7732463298862 59.665688397594)


Håvard

strk at refractions.net wrote:
> On Wed, Dec 21, 2005 at 10:10:01AM -0000, Mark Cave-Ayland wrote:
> 
>>>-----Original Message-----
>>>From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-
>>>bounces at postgis.refractions.net] On Behalf Of strk at refractions.net
>>>Sent: 21 December 2005 08:19
>>>To: PostGIS Users Discussion
>>>Subject: Re: [postgis-users] transform() does not do work for NGO1948 zone
>>>III-> WGS84 longlat (epsg:27393->epsg:4326)
>>>
>>>On Tue, Dec 20, 2005 at 04:56:47PM -0500, Frank Warmerdam wrote:
>>>...
>>>
>>>>Error -38 is:
>>>> 	"failed to load NAD27-83 correction file",  	/* -38 */
>>>>
>>>>So basically, if the datum shift files are not found, then the
>>>>code fallback to trying a conversion without the datum shift.
>>>
>>>Thank you Frank,
>>>maybe we should raise a WARNING in that case ? I mean, is
>>>"shift files not found" condition a sign of incomplete
>>>installation of PROJ4 ?
>>
>>I would say a warning should definitely be given if the transformation being
>>done is not the one that was requested by the user.
> 
> 
> I've added the warning:
> 
> 	elog(WARNING, "transform: failed to load NAD27-83 correction file");
> 
> But, I cannot reproduce the problem with this query:
> 
> 	select AsText(
> 		transform('SRID=27393;POINT(2836.394208896 185526.991186176)',
> 			4326)
> 	);
> 
> Even if I temporarly remove /usr/local/share/proj  ...
> Output is:
> 
> 	POINT(0.0464201635443672 59.6661916850467)
> 
> postgis_proj_version(): Rel. 4.4.8, 3 May 2004
> 
> Tips on how to reproduce the error (or is it possible PROJ4 would
> make the two attempts by itself ?) ?
> 
> --strk;
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
> 

-- 
Håvard Tveite
Department of Mathematical Sciences and Technology, UMB
Drøbakveien 14, POBox 5003, N-1432 Ås, NORWAY
Phone: +47 64965483 Fax: +47 64965401 http://www.umb.no/imt