[gdal-dev] Multidimensional raster support in GDAL
Ari Jolma
ari.jolma at gmail.com
Tue Nov 21 02:23:31 PST 2017
I'd like to get back to this topic a bit since I learned something from
the standards that I believe was not discussed in the earlier discussion
https://lists.osgeo.org/pipermail/gdal-dev/2017-October/047464.html
In WCS 1 the range of the data - remember the main conceptual division
to the domain (the X,Y, etc dimensions) and the range (the data if you
will) - consists of fields, which may consist of bands. That is, a field
may have an array value (an array of bands). In WCS 2, this separation
is, firstly, outsourced to SWE since the datatype of range is
SWE::DataRecord, and, secondly, left as further work in the range
subsetting extension. The current range subsetting extension makes no
difference between fields and bands, they are the same and there is no
structure.
The GDAL WCS driver has had some experimental support for time as field
and different time steps as bands. I'm not sure if there are many people
using it since I believe the functionality is currently broken when used
together with MapServer. The brokenness seems to be so serious that when
making a gdal_translate call where the source is a WCS that has a field
with more than one band (and GDAL recognizes it as such) and the call
does not involve scaling, the call fails. The reason seems to be that
gdal_translate accesses the data band by band.
I guess my point is here is that this is another difference between the
GDAL data model and the general coverage data model. The simple approach
to the data model mismatch is to allow GDAL datasets to be made from
coverage sources with queries. Also one thing I realized I need for the
new WCS driver is something which distinguishes different GDAL datasets
made from a single coverage.
Best regards,
Ari
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