[Gdal-dev] ECW registration information not recognised in ESRI

[Delfos, Jacob]

Hi All,

Have a bit of a mystery:

I am translating some geotiffs to ecw. These geotiffs have their geographic
information internally in the headers, as well as in a tfw file. They all
translate fine, and the coordinate information in the ecw file is recognised
in ESRI ArcGIS.

One TIFF file, however, I have modified in photoshop, so it lost its
geographic information in the header, but it still has its tfw file. When I
translate it to ecw (using the same command as for the other files), its
coordinate information is not recognised by ESRI ArcGIS. However, its
internal coordinate information IS recognised by other software (gdalinfo,
er viewer, global mapper, etc.). 

So when translating a TIFF with worldfile, the coordinate information seems
to exist internally in the ecw file, is recognised by most software, but not
by ArcGIS. To make it more interesting: If I translate the same file with
the freeware "ecw compressor" from ER Mapper, the resulting ecw file is
correctly referenced by ArcGIS.

In ER Viewer, the image properties are different: the one created by the
compressor has a WGS84 Datum, Coordinate System "Local", Coordinate type
"UTM (Eastings/Northings)" (which should be latlong). For the Gdal ECW,
these properties are set to "RAW".


The command I used:

C:\install\gdal\compiling\apps>gdal_translate -of ECW
C:\temp\gdal\SRTM4_tasmania_ACRES_trueColour.tif
C:\temp\gdal\SRTM4_tasmania_ACRES_trueColour.ecw -co "QUALITY=6"

Gdalinfo on the TIFF:
------------------------------------------------------------
Driver: GTiff/GeoTIFF
Size is 6150, 5217
Coordinate System is `'
Origin = (143.624867,-39.368522)
Pixel Size = (0.00083333,-0.00083333)
Metadata:
  TIFFTAG_SOFTWARE=Adobe Photoshop CS Windows
  TIFFTAG_DATETIME=2005:06:09 16:18:41
  TIFFTAG_XRESOLUTION=72
  TIFFTAG_YRESOLUTION=72
  TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
Corner Coordinates:
Upper Left  ( 143.6248668, -39.3685216)
Lower Left  ( 143.6248668, -43.7160216)
Upper Right ( 148.7498668, -39.3685216)
Lower Right ( 148.7498668, -43.7160216)
Center      ( 146.1873668, -41.5422716)
Band 1 Block=6150x1 Type=Byte, ColorInterp=Red
Band 2 Block=6150x1 Type=Byte, ColorInterp=Green
Band 3 Block=6150x1 Type=Byte, ColorInterp=Blue


Why is the coordinate information written to the header of the ECW file
different if a TFW is used? It's not a drama, but it would be nice if it
worked in ESRI.

Regards,

Jacob


JACOB DELFOS
SPATIAL INFORMATION ANALYST
Maunsell Australia Pty Ltd
629 Newcastle Street, Leederville, WA 6007
PO Box 81, Leederville, WA 6902
Western Australia
ABN 20 093 846 925

Tel     + 61 8 9281 6185
Fax    + 61 8 9281 6297
jacob.delfos at maunsell.com

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