ECW to GeoTiff Conversion missing Projection

[dgraham@…]

Frank:

Reciently one of our employees looked into using gdal_translate to convert ECW
files to Geotiff.  Here are his comments:

Dave Graham
------
Regarding the gdal_translate program for decompressing ECWs, I have good
news and bad news.

First, the good news:

gdal_translate is part of the gdal package that has been installed and
configured on most of the IP computers.  ECW support is part
of the standard package.  All you have to do to decompress the data is to
start a command window and type:

  gdal_translate path_to_input_file path_to_output_file

You can also run it in batch mode by having one line per image file in a
.BAT file.

Now, the (sort of) bad news:

gdal_translate does not carry over projection information.  It just carries
over corner coordinates.  So you have to run geotifcp or something similar
to set the projection of the output file.

And the (really) bad news:

gdal_translate is very slow.  It takes approximately 6 minutes to translate
one DOQQ file.  In comparison, saving the file out of ERViewer takes half a
minute.  To add insult to injury, the ERViewer-translated GeoTIFF keeps the
projection information.  You may be better off having a tech open these
files and save them out one at a time in ERViewer.

Another option is ECW2TIF EASI script.  Advantages: keeps georeferencing, much
faster than gdal_translate (approx. 1 min. per file).  Disadvantage:
requires PCI key, does not work in version 6.3.

All things considered, it looks like Jason's EASI script (or some
modification thereof) is the best option.

--Yusuf

[warmerdam]

Some degree of ECW coordinate system reading support has been implemented in
ecwdataset.cpp.  No write support is available yet.