[gdal-dev] gdalinfo coordinates problem?

[Hermann Peifer]

As far as I can see: lon_0 is the same in both cases and there is also 
no actual difference between +datum=NAD83 (gdal) and +ellps=GRS80 
+towgs84=0,0,0,0,0,0,0 (qgis).

I am not sure where +x_0=600000 (qgis) comes from, but gdal's +x_0 value 
is simply 6458320.416666666 * 0.3048006096012192 = 1968500 *meters*, so 
in fact only +units=us-ft is wrong there.

Hermann


On 2014-01-18 20:09, Etienne Tourigny wrote:
> I noticed that qgis-2.0 also has a problem with this file, but places it
> around 54 degrees west longitude (if using on-the-fly reprojection to
> WGS84).
>
> The CRS is different from that identified by gdal (the lon_0, units and
> datum are different)
>
> qgis:
> +proj=lcc +lat_1=40.96666666666667 +lat_2=39.93333333333333
> +lat_0=39.33333333333334 +lon_0=-77.75 +x_0=600000 +y_0=0 +ellps=GRS80
> +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
>
>
> gdal:
>
> PROJ.4 : '+proj=lcc +lat_1=40.96666666666667 +lat_2=39.93333333333333
> +lat_0=39.33333333333334 +lon_0=-77.75 +x_0=1968500 +y_0=0 +datum=NAD83
> +units=us-ft +no_defs '
>
> OGC WKT :
> PROJCS["NAD_1983_StatePlane_Pennsylvania_South_FIPS_3702_Feet",
>      GEOGCS["NAD83",
>          DATUM["North_American_Datum_1983",
>              SPHEROID["GRS 1980",6378137,298.2572221010002,
>                  AUTHORITY["EPSG","7019"]],
>              AUTHORITY["EPSG","6269"]],
>          PRIMEM["Greenwich",0],
>          UNIT["degree",0.0174532925199433],
>          AUTHORITY["EPSG","4269"]],
>      PROJECTION["Lambert_Conformal_Conic_2SP"],
>      PARAMETER["standard_parallel_1",40.96666666666667],
>      PARAMETER["standard_parallel_2",39.93333333333333],
>      PARAMETER["latitude_of_origin",39.33333333333334],
>      PARAMETER["central_meridian",-77.75],
>      PARAMETER["false_easting",6458320.416666666],
>      PARAMETER["false_northing",0],
>      UNIT["us_survey_feet",0.3048006096012192],
>      AUTHORITY["EPSG","32129"]]
>
>
>
>
> On Fri, Jan 17, 2014 at 8:37 PM, Even Rouault
> <even.rouault at mines-paris.org <mailto:even.rouault at mines-paris.org>> wrote:
>
>     Le vendredi 17 janvier 2014 21:28:35, Reynolds, Scott a écrit :
>      > Hi,
>      >
>      > I've downloaded several DEMs (e.g 27002570PAS_dem.zip) from
>      >
>     ftp://pamap.pasda.psu.edu/pamap_lidar/cycle1/DEM/South/2008/20000000/.
>      > Gdalinfo is reporting the corner coordinates to be in the
>     vicinity of  91
>      > degrees 31 minutes west longitude which should be more like 75
>     degrees 36
>      > minutes west longitude.  Can someone explain what is happening here?
>
>     GeoTIFF support for non-meter linear units has been a major source of
>     headaches in GDAL / libgeotiff. People will appreciate looking at
>     frmts/gtiff/gt_wkt_srs.cpp
>
>     I'm not sure if that GeoTIFF file is correct or not regarding the
>     values of the
>     false easting/northing with respect to the GeoTIFF spec (many in the
>     wild are
>     broken), but when looking at what happens, I noticed that a
>     transformation
>     from meters to feet happened twice. The attached patch fixes that
>     (and the
>     corner coordinates are around 75°), but I'm not sure if it is completely
>     correct in all cases.
>
>     You should likely create a GDAL Trac ticket with your report and the
>     patch,
>     but I'm not sure who will dare hurting his head against this wall...
>
>     Even
>
>      >
>      > Thanks,
>      > Scott
>
>     --
>     Geospatial professional services
>     http://even.rouault.free.fr/services.html
>
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