[Gdal-dev] reprojection

[Maciek Sieczka]

Hi!

I got a following GTiff from an SRTM bil file:

    Driver: GTiff/GeoTIFF
    Size is 1201, 1201
    Coordinate System is:
    GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.2572235630016,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree (supplier to define representation)",0.01745329251994328],
    AUTHORITY["EPSG","4326"]]
    Origin = (14.999583,51.000417)
    Pixel Size = (0.00083333,-0.00083333)
    Corner Coordinates:
    Upper Left  (  14.9995833,  51.0004167) ( 14d59'58.50"E, 51d 0'1.50"N)
    Lower Left  (  14.9995833,  49.9995833) ( 14d59'58.50"E, 49d59'58.50"N)
    Upper Right (  16.0004167,  51.0004167) ( 16d 0'1.50"E, 51d 0'1.50"N)
    Lower Right (  16.0004167,  49.9995833) ( 16d 0'1.50"E, 49d59'58.50"N)
    Center      (  15.5000000,  50.5000000) ( 15d30'0.00"E, 50d30'0.00"N)
    Band 1 Block=1201x3 Type=Int16, ColorInterp=Gray

Next I converted it into an "ETRS89 / Poland CS92" and then back into
GEOGCS.
Now the pixel size and the corner and centre coords are different:

    Pixel Size = (0.00085946,-0.00085946)
    Corner Coordinates:
    Upper Left  (  14.9142554,  51.0303873) ( 14d54'51.32"E, 51d 1'49.39"N)
    Lower Left  (  14.9142554,  49.9698135) ( 14d54'51.32"E, 49d58'11.33"N)
    Upper Right (  16.0633536,  51.0303873) ( 16d 3'48.07"E, 51d 1'49.39"N)
    Lower Right (  16.0633536,  49.9698135) ( 16d 3'48.07"E, 49d58'11.33"N)
    Center      (  15.4888045,  50.5001004) ( 15d29'19.70"E, 50d30'0.36"N)
    Band 1 Block=1337x3 Type=Int16, ColorInterp=Gray

I suspect that the answer is no (and that my question may be stupid) but I
want to know for sure: does it have to be like this or is there a way to
derive the genuine raster from a raster it was once reprojected to? Or to
improve the accuarcy at least?

Maciek