[gdal-dev] Does GDAL support ArcInfo Binary Grids with multiple bands?

[Jason Roberts]

Andrew and Peter,

Thanks for this info. I have not worked with ArcGIS grid stacks before so
this is very helpful.

I will append your comments to the ticket we started on this topic
http://trac.osgeo.org/gdal/ticket/3116. Frank deduced some of this already
and I came across some documentation (see link in the ticket) that concurs
with what you've said.

Best,
Jason

-----Original Message-----
From: Peter J Halls [mailto:P.Halls at york.ac.uk] 
Sent: Friday, August 28, 2009 7:15 AM
To: Andrew Loughhead
Cc: Jason Roberts; gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] Does GDAL support ArcInfo Binary Grids with multiple
bands?

Andrew is correct.  The ArcGIS grid stack comprises an index to the
component 
grids, stackname.stk. The records comprise the grid names.  The grids must
be in 
the same location (workspace) and have the same projection / coordinate
system 
but do not need to have the same geographic extents (so long as there is an
area 
of common overlap) or cell size.  Where the cell size differs, that quoted
for 
the stack is the coarsest of the components.

It is quite common to use a stack to collect together raster layers
representing 
disparate criteria in order to analyse them together, using geostats, for 
example.  A multi-band stack, such as, for example, might comprise a Landsat
TM 
image, is a sort of special case.

Peter

Andrew Loughhead wrote:
> Jason Roberts wrote:
>>
>> Is the GDAL ArcInfo Binary Grid (AIG) driver intended to support AIGs 
>> with multiple bands? I have a 5-band AIG for which the Python gdal 
>> bindings for GDAL 1.6.0 report "`C:\Temp\ccomp2' not recognised as a 
>> supported file format." ArcGIS 9.3.1 reports that the "format" of it 
>> is "GRID Stack 7.x". It was created using standard ArcGIS tools.
>>
> I don't think that its quite right to see a GRID stack as an AIG with 
> multiple bands.
>  From (somewhat long term) memory an ArcInfo Grid Stack is actually a 
> collection of individual grids, rather than a single grid dataset with 
> multiple bands.  Within ArcInfo Workstation stacks can be converted to a 
> few multiband image formats, and multiband images converted to stacks.  
> I *think* that Stacks always have an INFO file, possibly called 
> <stackname>.stk, and I also think that the grids composing a stack had 
> to have identical bounds, and be in the same workspace.  Any particular 
> grid in a workspace could be in zero, one or more stacks.
> 
> Anyway I would expect that GDAL will deal fine with the individual grids 
> in the stack, as individual datasets.  Any GDAL utility, or binding, 
> which can combine individual datasets into a multiband image could 
> therefore convert a stack into an image.  Of course you would need to 
> know which individual grids form the stack.
> hth
> Andrew
> 
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Peter J Halls, GIS Advisor, University of York
Telephone: 01904 433806     Fax: 01904 433740
Snail mail: Computing Service, University of York, Heslington, York YO10 5DD
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