[Qgis-developer] QGIS CRS handling question

[Otto Dassau]

Hi,

I would like to understand QGIS behavior a little better for CRS handling. 

I have a tif/tfw file (input.tif) and would like to create compressed geotiff
tiles from it (output.tif).

1) When I use

gdal_translate -co COMPRESS=JPEG -co PHOTOMETRIC=YCBCR -co TILED=YES \
 -a_srs EPSG:25833 input.tif output.tif

gdalinfo shows:

Driver: GTiff/GeoTIFF
Files: output.tif
Size is 16100, 15300
Coordinate System is:
LOCAL_CS["ETRS89 / UTM zone 33N",
    GEOGCS["ETRS89",
        DATUM["unknown",
            SPHEROID["unretrievable - using WGS84",6378137,298.257223563],
            TOWGS84[0,0,0,0,0,0,0]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433]],
    AUTHORITY["EPSG","25833"],
    UNIT["metre",1]]
[...]

loading this file in QGIS I am asked to provide the CRS for the layer,
although it should be written in the GeoTiff header. 

2) When I use 

gdal_translate -co COMPRESS=JPEG -co PHOTOMETRIC=YCBCR -co TILED=YES \
 -a_srs "+proj=utm +zone=33 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m \
 +no_defs" input.tif output.tif

gdalinfo shows:

Driver: GTiff/GeoTIFF
Files: output.tif
Size is 16100, 15300
Coordinate System is:
PROJCS["UTM Zone 33, Northern Hemisphere",
    GEOGCS["GRS 1980(IUGG, 1980)",
        DATUM["unknown",
            SPHEROID["GRS80",6378137,298.257222101],
            TOWGS84[0,0,0,0,0,0,0]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",15],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]]]


loading this file in QGIS, I am *not* asked to provide the CRS for the
layer, but QGIS assigns the wrong CRS. In my case I want EPSG 25833 but get
EPSG 3006 (which has the same parameters as 25833, but is not what I want).

How can I make QGIS read the CRS correctly? Does anybody has a solution for
this?

Thanks a lot
Otto