Hi Jean - we should keep this on the email list.
Can you try the code example and step through it with a debugger? This should
help explain why it will hep you.
1. You parse the WKT into a CoordinateReferenceSystem
2. You look for a matching CoordinateReferenceSystem coming out of the official
EPSG database
Inside that code it goes through and checks for a CoordinateReferenceSystem
with the same values as yours; ignoring the metadata (such as name and
description). The method is called "equalsIgnoresMetadata" if you are
interested.
3. It returns you a match ... and that match includes Bursa Wolf Parameters
Jody
On 17/05/2010, at 7:37 PM, Jean Marie wrote:
> Hi jody
>
> I had a look at the example given at :
>
> http://docs.codehaus.org/display/GEOTDOC/01+CRS+Helper+Class#01CRSHelperClass-SearchingforaCoordinateReferenceSystem
>
> I think you refer to the following code :
> -----
> String code = CRS.lookupIdentifier( example, true ); // should be "EPSG:4230"
> CoordinateReferenceSystem crs = CRS.decode( code );
> ------
>
> well I don't know how this can help me ;
>
> you talked also about an "Equals" method that could assist me ;
> well I don't see how
>
> if you could give me some further details it would be helpfull
> as I don't know how to sort out this problem of String WKT
> which sometimes contains all parameters required and sometimes doesn't
>
> thanks a lot
>
> Jean-Marie
>
>
> Subject: Re: [Geotools-devel] how to get Bursa-Wolf parameters in WKT strings
> From: jody.garn...@gmail.com
> Date: Thu, 13 May 2010 08:35:11 +1000
> CC: geotools-de...@lists.sourceforge.net
> To: jm...@hotmail.fr
>
> Hi Jean
>
> Here is what I kind of do; I use the CoordinateReferenceSystem created my WKT
> to look up the "Real" CoordinateReferenceSystem produced by the EPSG database
> (which is much more complete).
>
> There is an "Equals" method that ignores metadata to assist you with this;
> and because I find CoordinateReferenceSystem stuff difficult to manage by
> hand there should be a helper method ...
>
> Yes there is - indeed it is one of the use-cases covered by the user guide:
> -http://docs.codehaus.org/display/GEOTDOC/01+CRS+Helper+Class#01CRSHelperClass-SearchingforaCoordinateReferenceSystem
>
> Cheers,
>
> Jody
>
> On 13/05/2010, at 3:15 AM, Jean Marie wrote:
>
> Hello
>
> my purpose is to get a list of projection systems described in a WKT format
> (so using gt-epsg-hsql-2.6.3) ;
> and then to use these WKT representations to achieve tranformations using
> only
> the library gt-referencing-2.6.3.jar
>
> to get these WKT strings I use the following code :
>
> CoordinateReferenceSystem crsSrc =
> ReferencingFactoryFinder.getCRSAuthorityFactory("EPSG",
> null).createCoordinateReferenceSystem(EPSG);
> and then crsSrc.toWKT() gives the WKT specification for EPSG
>
> I took 3 WKT representations for respectively EPSG = "EPSG:4326", EPSG =
> "EPSG:2056" and EPSG = "EPSG:27572"
> then I created for each one a CoordinateOperationFactory object to carry out
> 2 transformations :
> one from 4326 to 2056 (Switzerland) et the other from 4326 to 27572 (France)
> using the WKT strings
>
> I noticed that the WGS84 to Swiss transformation is correct,
> while the WGS84 to French transformation generates an error saying that
> Bursa-Wolf parameters are required ;
>
> I would like to know how to sort out this problem as I need accurate results
> and I cannot afford to use the following code involving some transformation
> errors:
>
> CRS.findMathTransform(crsSrc, crsDest, true)
>
> is it possible to get Bursa-Wolf parameters in each WKT representation ?
>
> thanks a lot
>
> Jean-Marie
>
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