[Gdal-dev] writing to GRID

[Frank Warmerdam]

Prosperi, Paolo (SDRN) wrote:
> Hi all.
> I'm a newbie of GDAL and surely NOT a programmer.
> The standard executable of GDAL 1.3.1 works smoothly on my windows 2000
> platform until I try to write to esri grid formats.
> 
> In particular, when I use the command gdal_merge and the AAIGrid output
> format:
> 
> gdal_merge -o my-path\my-grid -of AAIGrid -n 0 my-image1 my-image2
> 
> I get as error:
> 
> 
> ERROR 6: GDALDriver::Create() ... no create method implemented for this
> format.
> 
> Traceback (most recent call last):
> 	File "C:\Programs\FWTools\bin\gdal_merge.py", line 450, in ?
> 	 t_fh.SetGeoTransform( geotransform )
> AttributeError: 'NoneType' object has no attribute 'SetGeoTransform'

Paolo,

I have added some error checking in gdal_merge.py to report this failure
more nicely.

> Instead, if I try to use the GIO driver:
> 
> gdal_merge -o %path%\my-image -of GIO -n 0 my-image1 my-image2
> 
> I simply get:
> 
> Format driver GIO not found, pick a supported driver.

Right.  In fact the GIO driver has been removed since 1.3.1 since it hardly
ever works properly.

> The question is:
> given I haven't got a clue on how to compile GDAL from source, is anybody so
> kind to pass me a windows executable version of GDAL with working GIO/AAIGrid
> driver?

You will just need to merge the file to a format that supports
direct creation and random writing such as GeoTIFF (driver name GTIFF) or
Erdas Imagine (driver name HFA).  Then use gdal_translate to convert to
AAIGRID.   Some drivers, such as the AAIGRID driver can only operate by
copying from a preexisting file.

eg.
   gdal_merge -o work.tif -n 0 my-image1 my-image2
   gdal_translate -of AAIGRID work.tif my.grd

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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