[gdal-dev] Trouble with French Ecw map

[Andre Joost]

Am 15.04.2015 um 01:23 schrieb Nicolas Ragg:
> Hello all
>
> I have a french map in ECW format, i guess it is from IGN. Srs seems ok
> but when i import
> the thing in qgis or try to warp the file it is all shifted to north
> (Around
> Sweden).
>
> The output from gdalinfo 1.11 is
> PROJ.4 : '+proj=lcc +lat_1=46.8 +lat_0=46.8 +lon_0=0 +k_0=0.99987742
> +x_0=600000 +y_0=200000 +a=6378249.2 +b=6356515 +to
> wgs84=-168,-60,320,0,0,0,0 +pm=paris +units=m +no_defs '
>
> OGC WKT :
> PROJCS["NTF (Paris) / Centre France (deprecated)",
>      GEOGCS["NTF (Paris)",
>          DATUM["Nouvelle_Triangulation_Francaise_Paris",
>              SPHEROID["Clarke 1880 (IGN)",6378249.2,293.4660212936265,
>                  AUTHORITY["EPSG","7011"]],
>              TOWGS84[-168,-60,320,0,0,0,0],
>              AUTHORITY["EPSG","6807"]],
>          PRIMEM["Paris",2.33722917,
>              AUTHORITY["EPSG","8903"]],
>          UNIT["grad",0.01570796326794897,
>              AUTHORITY["EPSG","9105"]],
>          AUTHORITY["EPSG","4807"]],
>      PROJECTION["Lambert_Conformal_Conic_1SP"],
>      PARAMETER["latitude_of_origin",52],
>      PARAMETER["central_meridian",0],
>      PARAMETER["scale_factor",0.99987742],
>      PARAMETER["false_easting",600000],
>      PARAMETER["false_northing",200000],
>      UNIT["metre",1,
>          AUTHORITY["EPSG","9001"]],
>      AXIS["X",EAST],
>      AXIS["Y",NORTH],
>      AUTHORITY["EPSG","27592"]]
>
> if i use this proj4 (from another map) (+proj=lcc +lat_1=45.89891888888889
> +lat_2=47.69601444444444 +lat_0=46.8 +lon_0=2.337229169999754 +x_0=600000
> +y_0=2200000 +a=6378249.2 +b=6356515.000000472 +units=m +no_defs)
> it is somehow better.

The false northing of both projection definitions differs by 2000 km. 
That is probably the reason why you get the shift.

HTH,
André Joost