[gdal-dev] Re: GDAL GeoPDF support

[Even Rouault]

Hi Robert,

> Hi Even,
> You are the lead for GeoPDF correct?

I wouldn't say that like that, but yes I wrote the driver.

> Thanks for putting this option within
> GDAL.  Great service.  I want to help and support more Datums, but I
> wanted to ask you what kind of work is required to do this. Can you give
> me a description of what needs to be done to add Projection support.  I am
> not sure yet why GDAL cannot understand my GeoPDF.

I don't see anything wrong in the output of gdalinfo. GDAL seems to understand 
correctly your PDF. The fact that the PROJCS description string is 'unnamed' 
isn't an issue. It just means that there is no particular name for a 
Transverse_Mercator projection on WGS84 datum with central_meridian = -99.5 
and latitude_of_origine != 0. When building back the WKT for the SRS of the 
PDF, the driver has logic to guess the PROJCS name for just a few of the most 
common SRS, like the UTM projections on WGS84 and a few others. The others 
will stay unnamed, but it shouldn't matter. By the way I couldn't find this 
projection in the EPSG dictionnary, so it has probably no name at all.

If you didn't see a warning like 'Unhandled (yet) value for Datum : XXXX. 
Defaulting to WGS84...' in the console, it means that the datum in the file was 
really WGS84, so at first sight, everything seems to be right.

> I know that the
> metadata embedded in the PDF file is all there.  I current have a GeoPDF
> map of mexico which has the following gdalinfo: Driver: PDF/Geospatial
> PDFFiles: c:\geopdf\mexico.pdfSize is 6372, 5072Coordinate System
> is:PROJCS["unnamed",    GEOGCS["WGS 84",        DATUM["WGS_1984",        
>    SPHEROID["WGS 84",6378137,298.257223563,              
>  AUTHORITY["EPSG","7030"]],            TOWGS84[0,0,0,0,0,0,0],          
>  AUTHORITY["EPSG","6326"]],        PRIMEM["Greenwich",0,          
>  AUTHORITY["EPSG","8901"]],        UNIT["degree",0.0174532925199433,      
>      AUTHORITY["EPSG","9108"]],        AUTHORITY["EPSG","4326"]],  
>  PROJECTION["Transverse_Mercator"],  
>  PARAMETER["latitude_of_origin",18.33333333333333],  
>  PARAMETER["central_meridian",-99.5],  
>  PARAMETER["scale_factor",0.9996],    PARAMETER["false_easting",0],  
>  PARAMETER["false_northing",0]]GeoTransform =  -139312.767126,
> 44.02043807999999, 0.14064624  221574.863831, 0.12083184,
> -44.05555728Metadata:  NEATLINE=POLYGON ((-136371.49610477735
> 218423.09941881828,137294.39917355074
> 219174.28580209854,138251.35443593346
> 2894.4713489619025,-136210.56288904281
> 1074.355416633829,-136637.11588929727
> 218155.67013899569,-136371.49610477735 218423.09941881828))Corner
> Coordinates:Upper Left  ( -139312.767,  221574.864)Lower Left  (
> -138599.409,   -1874.923)Upper Right (  141185.464,  222344.804)Lower
> Right (  141898.822,   -1104.982)Center      (    1293.027,
>  110234.941)Band 1 Block=6372x1 Type=Byte, ColorInterp=RedBand 2
> Block=6372x1 Type=Byte, ColorInterp=GreenBand 3 Block=6372x1 Type=Byte,
> ColorInterp=Blue
> 
> What would I need to do to add more support for Projection to get rid of
> "unnamed"?? Thanks,
> Robert