[Mapserver-users] Projection AUTO, GDAL and ECW files

[Frank Warmerdam]

Brent Fraser wrote:
> Frank (and others),
>  
>   I'm doing some investigation into making the TILEINDEX feature a 
> little more flexible with respect to coordinate systems.  I like the 
> PROJECTION AUTO feature added to MapServer 3.7 for datastores, but not 
> all of them store coordinate system information with the data (e.g. 
> shapefiles, jpg), and some of them have their own "proprietary" method 
> of specifying it (e.g. ECW) not handled by GDAL.  This means that 
> integrating new datasets requires Mapserver implementors to carefully 
> define the coordinate system in each map file.
>  
>   What do you think about having GDAL read an additional file that 
> specifies the coordinate system definition for a specific data file?  
> The file could/should have the same filename prefix as the datafile with 
> an extension of prj, csd or something that hasn't been used for similar 
> things.  The format could be PROJ strings (or EPSG numbers, or OGIS WKT 
> format).

Brent,

I think it would be reasonable for GDAL drivers for formats that no
inherent coordinate system support to allow using .prj files.  However,
in the case of the ECW driver the real solution is to fix the damn thing.

However, I am in no immediate danger of implementing such a .prj file
fallback feature for all the coordinate-system-less drivers at this time.
We could however conceivable implement the same thing within MapServer
much like the .wld file fallback code is/was working in mapserver.
Basically, if GDALGetProjectionRef() doesn't return something helpful, just
check for a .prj file and use that if present.

Best regards,

-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent