RE: [udig-devel] Re: CRS - "Bursa wolf parameters required."

["Dean C. Mikkelsen" <dcmikkelsen@xxxxxxx>]

Just an idea...I've been following this Bursa-wolf thread since the
start.

The EPSG has implemented the code into a SQL for MySQL. With some
modifications to the SQL, could it not be implemented into PostGIS and
become part of the data model. Hence the codes could be looked up in the
DB, rather than maintaining an external file. 

I'm based in North Vancouver, a geodesist by training, and was involved
in the APSG and EPSG over my past 11 years. I was in oil and gas
exploration data management and GIS.

I am relatively new to uDig and MapServer, but learning the ropes pretty
quickly.

I may be totally off the boat here, but then again, it's just an idea.

Kind regards,
Dean

Dean C. Mikkelsen, B.Sc., P.Eng.
Terra ETL Ltd.
Phone: 604-929-8630
E-mail: dcmikkelsen@xxxxxxx



-----Original Message-----
From: udig-devel-bounces@xxxxxxxxxxxxxxxxxxxxx
[mailto:udig-devel-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of Paul
Ramsey
Sent: April 20, 2005 3:37 PM
To: User-friendly Desktop Internet GIS
Subject: Re: [udig-devel] Re: CRS - "Bursa wolf parameters required."

Direct GeoTools access to the EPSG database is a "great idea" that noone

has actually implemented. It was once implemented, but is not working 
now. The only "epsg" data we have now is a WKT properties files I hacked

up many moons ago, precisely because the EPSG database was not working /

ready.

Yes, if we had an ESPG database, the DatumAliases could also reference 
an EPSG datum ID, which in turn would allow us to look up transforms 
between those actual datums, which would be very nice. But we would 
still need to do the DatumAliases trick.

P

Matthias Basler wrote:

> Paul Ramsey wrote
> 
>>One thing we can do (prepare for the pain) is to add yet more
>>information to our DatumAliases -- for each DatumAlias, add the BW
>>transform parameters to WGS84. That way, if we come across a
particular
>>datum name, but lack TOWGS[] information, we can fill it in ourselves.
>>Otherwise it'll be death and destruction quite frequently: most apps
>>generating WKT do *not* generate the TOWGS[] portions of the WKT.
> 
> 
> Maybe this is a very stupid question: Doesn't support GeoTools the use
of the
> EPSG database for getting the transformation parameters? AFAIK most
CRS are
> exactly defined in the EPSG database (including Bursa wolf parameters
and other
> means of reprojection), so all missing information can be retrieved
from it,
> cannot it?
> 
> Since I'm interested in the reprojection functionality myself, maybe
someone can
> shortly outline to me how this currently handled in uDig/GeoTools2.1.
> 
> Matthias Basler
> c9bama@xxxxxxxxxxx
> 
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