[Qgis-user] Projection problem in QGIS 1.7.2 between EPSG 31370 and EPSG:3035

[Etienne Tourigny]

It might be because the TOWGS84 parameters are missing in the .prj
files, but present in the EPSG definitions for the "Belge 1972"
GEOGCS.

Either something is wrong with the TOWGS84 definition in EPSG:31370 or
the datum shift was not done in NATURA2000__PERIMETRES.shp ?

For example (using gdalsrsinfo from GDAL 1.9)

$ gdalsrsinfo -o proj4 EPSG:31370

PROJ.4 : '+proj=lcc +lat_1=51.16666723333333 +lat_2=49.8333339
+lat_0=90 +lon_0=4.367486666666666 +x_0=150000.013 +y_0=5400088.438
+ellps=intl +towgs84=-106.869,52.2978,-103.724,0.3366,-0.457,1.8422,-1.2747
+units=m +no_defs '

$ gdalsrsinfo -o proj4 NATURA2000__PERIMETRES.prj

PROJ.4 : '+proj=lcc +lat_1=49.8333339 +lat_2=51.16666723333333
+lat_0=90 +lon_0=4.367486666666666 +x_0=150000.01256 +y_0=5400088.4378
+ellps=intl +units=m +no_defs '

and the wkt definitions:

$  gdalsrsinfo -o wkt -p EPSG:31370

PROJCS["Belge 1972 / Belgian Lambert 72",
    GEOGCS["Belge 1972",
        DATUM["Reseau_National_Belge_1972",
            SPHEROID["International 1924",6378388,297,
                AUTHORITY["EPSG","7022"]],
            TOWGS84[-106.869,52.2978,-103.724,0.3366,-0.457,1.8422,-1.2747],
            AUTHORITY["EPSG","6313"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4313"]],
    PROJECTION["Lambert_Conformal_Conic_2SP"],
    PARAMETER["standard_parallel_1",51.16666723333333],
    PARAMETER["standard_parallel_2",49.8333339],
    PARAMETER["latitude_of_origin",90],
    PARAMETER["central_meridian",4.367486666666666],
    PARAMETER["false_easting",150000.013],
    PARAMETER["false_northing",5400088.438],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AXIS["X",EAST],
    AXIS["Y",NORTH],
    AUTHORITY["EPSG","31370"]]

$  gdalsrsinfo -o wkt -p NATURA2000__PERIMETRES.prj

PROJCS["Belge_Lambert_1972",
    GEOGCS["GCS_Belge_1972",
        DATUM["Reseau_National_Belge_1972",
            SPHEROID["International_1924",6378388.0,297.0],
            TOWGS84[-106.869,52.2978,-103.724,0.3366,-0.457,1.8422,-1.2747]],
        PRIMEM["Greenwich",0.0],
        UNIT["Degree",0.0174532925199433]],
    PROJECTION["Lambert_Conformal_Conic_2SP"],
    PARAMETER["False_Easting",150000.01256],
    PARAMETER["False_Northing",5400088.4378],
    PARAMETER["Central_Meridian",4.367486666666666],
    PARAMETER["Standard_Parallel_1",49.8333339],
    PARAMETER["Standard_Parallel_2",51.16666723333333],
    PARAMETER["Latitude_Of_Origin",90.0],
    UNIT["Meter",1.0]]


On Sat, Dec 24, 2011 at 1:22 PM, Giovanni Manghi
<giovanni.manghi at faunalia.pt> wrote:
>
>> In fact, when the CRS is set in project properties TO EPSG: 3035, both
>> shapefiles match as Giovanni noticed it. But when the project-wide CRS
>> is set to EPSG: 31370, the shift appears.
>
>> If you want to have a try, here are the links to the freely donwloadable
>> shapefiles:
>>        - belgian (Walloon Region) Natura 2000 limits:
>> http://environnement.wallonie.be/cartosig/telechargement/NATURA2000_DIFFUSION_BASE_MARS2010.zip
>
>
> QGIS doesn't match this layers exactly with epsg 31370. If you use the
> custom CRS it created when you load the layer, then there is no shift.
>
> cheers
>
> -- Giovanni --
>
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