[Gdal-dev] newbie question about AIG vs. GIO drivers

[Frank Warmerdam]

Gregory, Matthew wrote:
> I have been combing through the prior postings to the list, but haven't come across an answer.  I apologize if this has been covered before ...
> 
> I am trying to sort out which is the "best" driver to use when reading in ArcInfo binary grids.  It appears that the GIO driver has preference (based on its position in GDALLAllRegister) and will allow writing grids, whereas the AIG driver will not.  However, the GIO driver lacks any projection definition capabilities at present(?).  
> 
> I can't find any documentation on the GIO driver as it appears to point to a missing link.(http://remotesensing.org/gdal/frmt_various.html#GIO)
> 
> Any guidance on this would be very helpful.  GDAL promises to be very useful ...

Matt,

In theory the GIO driver is better because it uses ESRI's own libraries
to read the file, so it might work for files that the AIG driver fails
on due to some misunderstanding of the format on my part.  However, in
practice, the AIG driver is better maintained and has projections support
which are omitted from the GIO driver because there was little interest.

Furthermore, I believe I dropped support for the GIO for the 1.1.9 release
(or perhaps it was since then) because it was generally more trouble than
it was worth.  The creating of files seems to be pretty buggy and the
read was not as good (in some ways) as the AIG especially once I finally
susses out the last weird compression type so the AIG now supports all
grid forms I have seen.  The docs presumably disappeared as part of this
"cleaning out" of the GIO driver.

However, recently a client has requested that I refresh the GIO driver, and
fix up the output support properly, so you should see it again in the
next major release.

Best regards,

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