[postgis-users] Question on transform.

[Luis Mota]

Just one aditional question: what kind of transformations are known to 
work correctly in PostGis? I'd like to control the transformations I 
make, to avoid wrong results.

I've been trying a little bit, and the results seem very odd to me...

Thanks again, Luís

Paul Ramsey wrote:

> Luis,
> You can confirm on the proj4 mailing list (try this out using the 
> proj4 commandline tools) but my understanding is that proj4 mostly 
> ignores geogcs transforms. There are a few exceptions to this rule, 
> but it is mostly true, since proj4 was originally written without any 
> geogcs transform support at all. The support which is there was 
> retrofitted in later by Frank Warmerdam.
> Frank can correct me, of course... :)
> Paul
>
> Luis Mota wrote:
>
>> Hi everyone.
>>
>> I've been using the transform function, but I have some surprising 
>> results...
>>
>> For instance, if I issue the following query:
>>
>> select transform(geomfromtext('POINT(0 38)',4803),4326);
>>
>> the result I get is:
>>       transform      -----------------------
>> SRID=4326;POINT(38 0)
>> (1 row)
>>
>> ie, exacly the same point... This is obviously wrong, since the two 
>> GEOGCS's are different. For instance, the prime meridian is different..
>>
>> Is it possible that I have some instalation problem? Was this a bug 
>> corrected in a later version?
>>
>> Thanks for any help.
>>
>
>