[Gdal-dev] gdalwarp UTM->SPCS

[Frank Warmerdam]

Richard Greenwood wrote:
> Hello;
> 
> I am continuing to struggle with gdalwarp. Following up on my earlier 
> query to this list - I am trying to reproject from UTM to state plane. 
> My source image has a world file, but an incomplete SRS, so I am 
> launching gdalwarp with both a s_srs and a t_srs where the s_srs defines 
> my UTM zone, and the t_srs defines my state plane zone. Is this 
> generally the right approach?
> 
> I have tried specifying both the s_srs and t_srs with EPSG:xxxx, PROJ.4 
> declarations, and OGC WTK in text files, but in no case am I getting the 
> expected results. For example, in no case does gdalinfo list the correct 
> units for my output file. I have specifed 
> UNIT["Foot_US",0.30480060960121924] in the t_srs WKT definition and 
> +to_meter=0.3048006096012192 and +unit=ft in the proj.4 t_srs 
> definitions, but the output always ends up as either 
> UNIT["metre",1,AUTHORITY["EPSG","9001"] or UNIT["unknown",1].
> 
> I feel like I must be overlooking someting terribly obvious. Where might 
> I find more examples of gdalwarp usage? Is there a more appropriate list 
> to pose the questions to?

Rich,

I appologise for not responding to your earlier message yet.  I have been
bogged down in deliverables, and an addiction to an MMORPG (www.atitd.com).

I tried something similar to your earlier example with a UTM 11 file I
have here, and it seemed to work pretty well.  I used this command:

   gdalwarp
   -s_srs "+proj=utm +ellps=GRS80 +zone=11 +north +datum=NAD83 +units=m +no_defs"
   -t_srs "+proj=tmerc +ellps=GRS80 +units=ft +lon_0=-110.0833333333 +lat_0=40.5
        +x_0=800000 +y_0=100000 +k=0.9999375 +no_defs"
   -order 3 openev/utm.tif nw.tif

Unlike your experience, my output did seem to get the right linear units:

Coordinate System is:
PROJCS["unnamed",
     GEOGCS["unnamed",
         DATUM["unknown",
             SPHEROID["unnamed",6378137,298.2572221010042]],
         PRIMEM["Greenwich",0],
         UNIT[,0.0174532925199433]],
     PROJECTION["Transverse_Mercator"],
     PARAMETER["latitude_of_origin",40.5],
     PARAMETER["central_meridian",-110.0833333333],
     PARAMETER["scale_factor",0.9999375],
     PARAMETER["false_easting",2624671.916010499],
     PARAMETER["false_northing",328083.9895013123],
     UNIT["foot",0.3048,
         AUTHORITY["EPSG","9002"]]]

Based on that, I now wonder what is different about your build and mine.
Are you building from a recent CVS update?  I suggest we try to isolate
this issue off the list today if you have the time.

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