Thanks Even, The method importFromEPSG() and the EPSG file look like what I'm looking for. I'll investigate it further.
Thanks, Paul *Paul Meems * Release manager, configuration manager and forum moderator of MapWindow GIS. www.mapwindow.org Owner of MapWindow.nl - Support for Dutch speaking users. www.mapwindow.nl * * 2011/5/11 Even Rouault <[email protected]> > Le mercredi 11 mai 2011 20:20:51, Paul Meems a écrit : > > Hi List, > > > > We use GDAL with Proj.4 in MapWindow GIS. > > We're currently in the process of upgrading to GDAL v1.8 > > > > We have some issues with projections in MapWindow. > > We partially us GDAL methods and partially our custom ones. > > We also are more and more working with EPSG codes with WMS and WFS. So we > > need to handle them as well. > > > > I've seen a discussion about this 2 or 3 weeks ago and my question > > partially overlaps. > > As I understand it, it is not possible do use GDAL/Proj.4 to input a EPSG > > code and get the prj-file or projection string back, right? > > If I were you, I would look at the importFromEPSG() and exportToProj4() / > exportToWkt() methods of OGRSpatialReference .... > > > And the same is for the other way round: get the EPSG code when the input > > is a projection string. > > Generally not, unless there's a AUTHORITY node in the WKT. There's also a > OGRSpatialReference::AutoIdentifyEPSG() method, but it will work only in a > few > cases. Have a look at its implementation to know which ones. > > One possibility to identify the EPSG code is to iterate over all the EPSG > code > and get their proj4 representation, and compare that to the proj4 > representation of your projection string. But that's not a perfect solution > and I'm not sure there's a perfect solution. The proj4 representation isn't > a > bijection of the WKT representation. > > > > > But we do want this. Is some sort of offline database or XML file > available > > that will show the EPSG codes with the accompanying prj-file text and > > projection string? > > Are you looking for the "epsg" file from the proj.4 distribution... ? > http://trac.osgeo.org/proj/browser/trunk/proj/nad/epsg > > Illustrating my point in previous paragraph : > > # CHTRF95 > <4151> +proj=longlat +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +no_defs <> > # NAD83(HARN) > <4152> +proj=longlat +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +no_defs <> > > 2 EPSG codes, same PROJ.4 representation > > > > > Or am I thinking in the wrong direction? > > > > Thanks, > > > > Paul > > > > > > *Paul Meems * > > Release manager, configuration manager > > and forum moderator of MapWindow GIS. > > www.mapwindow.org > > > > Owner of MapWindow.nl - Support for > > Dutch speaking users. > > www.mapwindow.nl > > > > * > > * >
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