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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