[Gvsig_english] trouble with EPSG 2154 and 27561

Fri Jul 16 15:36:17 CEST 2010

There seems to be a problem with datum shifts and the
version of the PROJ4 library that comes with gvSIG OADE.
I'll take a closer look next week.

Ben

----- Original Message -----
> Hello,
> 
> 50m is with OADE 2010 !!!
> With gvsig 1.9 it's only 1.4 m (that is right with the precision of
> the datum shift)
> 
> If I create an user CRS with a copy of 27561 where I only change the
> central meridian, I have the same result that with your proposal of
> user CRS. I think that there is a problem with meridian "non Grenwich"
> in lambert conformal conic 1SP.
> 
> 
> Regards,
> 
> Michel Bouillot
> 
> ----- Mail Original -----
> De: "Bouillot Michel" <michel.bouillot at montreuil.fr>
> À: "Users and Developers mailing list"
> <gvsig_internacional at listserv.gva.es> Envoyé: Vendredi 16 Juillet 2010
> 11:08:16
> Objet: Re: [Gvsig_english] trouble with EPSG 2154 and 27561
> 
> 
> Hello,
> 
> Thanks for the answer.
> The process works but I find an error of about 50m.
> I take time to study it and I tell you.
> 
> Regards
> 
> Michel Bouillot
> 
> ----- Mail Original -----
> De: "Juan Lucas Dominguez Rubio" <jldominguez at prodevelop.es>
> À: "Users and Developers mailing list"
> <gvsig_internacional at listserv.gva.es>, "Users and Developers mailing
> list" <gvsig_internacional at listserv.gva.es>
> Envoyé: Vendredi 16 Juillet 2010 10:04:27
> Objet: Re: [Gvsig_english] trouble with EPSG 2154 and 27561
> 
> 
> 
> Hello, Michel:
> 
> I think there's some confusion about the meaning of the EPSG codes.
> According to spatialref.org, the PRJ file for EPSG:27561 is this:
> 
> http://spatialreference.org/ref/epsg/27561/prj/
> 
> But that file is not like the one that comes with your shapefile.
> 
> gvSIG is probably using the definition found in the spatialref.org
> website, so that's why your shapefiles do not match if you select
> EPSG:27561 when adding that file to your view.
> 
> According to spatialref.org, the CRS that matches your PRJ file is
> 'NTF Lambert Zone 1 France 2SP' (code SR-ORG:6910):
> 
> http://spatialreference.org/ref/sr-org/6910/prj/
> 
> So all you have to do is declare it as a user-defined CRS in gvSIG.
> 
> This has worked for me (I'll refer to your files as montreuil_2154.shp
> and montreuil_27561.shp):
> 
> - from the project manager, click 'New' to create a new view. Select
> it (without opening it) and click on 'Properties'
> - clic on the [...] button to change the view's CRS
> - choose 'Type: user CRS' and click on 'New'
> - choose the 'From WKT' option and paste this paragraph in the text
> box:
> 
> PROJCS["unnamed",GEOGCS["unnamed
> ellipse",DATUM["unknown",SPHEROID["unnamed",6378249.2,293.4660200000053],TOWGS84[-168,-60,320,0,0,0,0]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic_2SP"],PARAMETER["standard_parallel_1",48.5985227778],PARAMETER["standard_parallel_2",50.3959116667],PARAMETER["latitude_of_origin",49.5],PARAMETER["central_meridian",2.3372291667],PARAMETER["false_easting",600000],PARAMETER["false_northing",200000],UNIT["Meter",1],AUTHORITY["EPSG","12345"]]
> 
> - click on 'Finalize' and 'Accept'. You'll see that gvSIG refers to
> the new CRS as 'USR:1' or similar.
> - click 'Accept' again and open the view
> - add the file montreuil_27561.shp without any additional option
> because we know it's the same CRS of the view.
> - go to the 'Add file' option again, choose the file
> montreuil_2154.shp and before clicking on 'Accept', click on the
> button to indicate the CRS of the file that is being added. Search for
> EPSG:2154 (this one has no problem, you can use it) and select it,
> then you need to choose the 'Manual transformation' option in the
> transformation combo box. The seven parameters are:
> 
> 168
> 60 -320
> 0 0
> 0 0
> 
> - click 'Accept' on all the following dialogs, and both shapefiles
> should match. There is a small error of about 1.5 m, but I don't think
> that's a problem for you.
> 
> Does this process work for you?
> 
> The CRS you have defined should be available from now on, but you will
> have to type the seven parameters each time from the 'Manual
> transformation' option.
> 
> Those seven parameters are valid if the view is in 'NTF Lambert Zone 1
> France 2SP'. If the view is in EPSG:2154 and you add a shapefile in
> 'NTF Lambert Zone 1 France 2SP', you'll have to reverse the sign of
> the parameters.
> 
> If you don't want to deal with user CRS and parameters inside gvSIG,
> you can reproject your shapefiles before starting gvSIG. There is a
> nice free program that does that:
> 
> http://fwtools.maptools.org
> 
> The command would be something like:
> 
> ogr2ogr -f "ESRI Shapefile" -s_srs epsg:2154 -t_srs epsg:27561
> new_file.shp old_file_2154.shp
> 
> (but again, we should check the meaning of EPSG:27561 in that case)
> 
> 
> Regards,
> 
> Juan Lucas Domínguez Rubio
> ---
> 
> Prodevelop SL, Valencia (España)
> 
> Tlf.: 96.351.06.12 -- Fax: 96.351.09.68
> http://www.prodevelop.es
> ---
> 
> 
> De: gvsig_internacional-bounces at listserv.gva.es en nombre de Bouillot
> Michel Enviado el: jue 15/07/2010 14:22
> Para: Users and Developers mailing list
> Asunto: Re: [Gvsig_english] trouble with EPSG 2154 and 27561
> 
> 
> 
> Hello,
> 
> I think that you are right.
> 
> I join shapefiles in both EPSG.
> 
> Thanks for the tests.
> 
> Regards,
> 
> Michel Bouillot
> 
> ----- Mail Original -----
> De: "Juan Lucas Dominguez Rubio" <jldominguez at prodevelop.es>
> À: "Users and Developers mailing list"
> <gvsig_internacional at listserv.gva.es>, "Users and Developers mailing
> list" <gvsig_internacional at listserv.gva.es>
> Envoyé: Jeudi 15 Juillet 2010 13:29:45
> Objet: Re: [Gvsig_english] trouble with EPSG 2154 and 27561
> 
> 
> 
> Hello, I think there's a misunderstood.
> 
> gvSIG is able to do on-the-fly reprojection (this is what Michel
> needs, I think).
> 
> But I'm afraid that, even if he follows the right steps to do it, the
> result will be wrong because (I think) gvSIG does not know the right
> parameters to perform that conversion (between EPSG:2154 and
> EPSG:27561).
> 
> There have been problems with the French projections in the past, and
> I'm not sure if they were caused by a bug in gvSIG or in the libraries
> used by gvSIG (especially Proj4).
> 
> Michel: can you please send to the list two little shapefiles (one in
> EPSG:2154 and the other in EPSG:27561) that should match but do not
> match in gvSIG? So we can also do some tests.
> 
> Regards,
> 
> 
> Juan Lucas Domínguez Rubio
> --- Prodevelop SL, Valencia (España)
> 
> Tlf.: 96.351.06.12 -- Fax: 96.351.09.68
> http://www.prodevelop.es
> ---
> 
> 
> De: gvsig_internacional-bounces at listserv.gva.es en nombre de Bouillot
> Michel Enviado el: jue 15/07/2010 13:02
> Para: Users and Developers mailing list
> Asunto: Re: [Gvsig_english] trouble with EPSG 2154 and 27561
> 
> 
> 
> Hi,
> 
> Thanks for this explanation.
> 
> I find GVSIG very good but in France we have just changed of RS. We
> begin to have data in the 2 RS.
> The reprojection in the view would be very pactical !
> Is there a hope for a such function in the futur ?
> 
> Regards
> 
> Michel Bouillot
> 
> 
> ----- Mail Original -----
> De: "Guillermo Tamburini" <tamburini_gui at gva.es>
> À: "Users and Developers mailing list"
> <gvsig_internacional at listserv.gva.es> Envoyé: Jeudi 15 Juillet 2010
> 12:43:50
> Objet: Re: [Gvsig_english] trouble with EPSG 2154 and 27561
> 
> Hi,
> 
> In fact, you can't correctly represent data in different reference
> systems in the same View (without reporojecting, it have no sense).
> 
> There are some software applications which applies automatically the
> reprojection, but it is not the case in gvSIG with vector layers.
> 
> First of all, you have to select the correct RS for your View, and
> then load the data (the target RS you are going to work).
> 
> Otherwise, you will see your data but in a incorrect situation. In
> other utm spindle, or displaced...
> 
> If your data is in different RS, you will have to reproject it.
> Goprocessing tools->Data Conversion->Reproject; the layer in the not
> current projection to the current projection.
> 
> Regards
> 
> 
> Bouillot Michel wrote:
> 
> 
> 
> 
> Hello,
> 
> I try to open in the same view one shp in EPSG 2154 and one SHP in
> EPSG 27561 but it don't match correctly. There is a problem with the X
> like a translation witch have a value who seems to be the difference
> between Greenwich and Paris meridian.
> 
> How to correct this trouble ?
> 
> regards
> 
> Michel Bouillot
> Chef de projet SIG
> 01 48 70 63 23 / michel.bouillot at montreuil.fr
> Ville de Montreuil / Direction Urbanisme et Habitat
> Service Études Développement Urbain
> 3, rue de Rosny / 93100 Montreuil
> 
> 
> _______________________________________________ Gvsig_internacional
> mailing list Gvsig_internacional at listserv.gva.es
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> 
> -- Guillermo Tamburini Beliveau
> Proyecto gvSIG
> Consellería de Infraestructuras y Transportes (GVA)
> Valencia (Spain)
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