[gdal-dev] How to represent multi-dimensional array

Michael Sumner mdsumner at gmail.com
Thu Jun 17 17:45:45 EDT 2010


I don't think there is a GIS that does this in a natural way - all you
can do is read in multiple slices. If the order of your axes really is
time, x, y, z then you will have y.n * z.n  (time, x) slices (as
bands) when read by GDAL - NetCDF will tend to store dimensions in
reverse order to the natural one, and I think GDAL reverses that - but
you can tell by the dimension and number of your bands, and the named
metadata on the GDAL bands.

Later versions of ArcGIS allow time-sliced arrays I think, so you
could store several of these.

NetCDF cannot store multi-attribute arrays (it will store several
same-size, same-metadata arrays for that purpose), so one thing you
could do is allow the GIS to to store several multi-band arrays (an
array for each T, a band for each Z)  - but you need to wear the
inconsistency of mixing attributes with dimensions.

Manifold reads in multiple rasters and I presume ArcGIS does too.

Eonfusion will do its best to read the array in its natural state, but
it is interpreted through GDAL and the dimensions reconstructed from
the band metadata, but it's not a traditional GIS in any sense.

R can read NetCDF natively or with GDAL (RNetCDF, ncdf, rgdal
packages) and convert to the Spatial classes, but these are limited to
multi-band 2D arrays.

Cheers, Mike.

On Fri, Jun 18, 2010 at 5:15 AM, Christopher Barker
<Chris.Barker at noaa.gov> wrote:
> Hi folks,
>
> I have a dataset that is a 4-dimensional array of values: time,x,y,z
>
> We're currently using netcdf to store it, which is well suited to this kind
> of data.
>
> However, we also need to get it into a GIS (Arc in this case), and I'm
> trying to find a good way to do that.
>
> Both Arc and gdalinfo do strange things if I simply point them at the netcdf
> file. GDAL seems to (arbitrarily?) see it as a 9064 band data set, so it is
> taking particular slice (I think I'm getting a bunch of (time, z) 2-d bands.
>
> Anyway, I suspect that if I re-arrange the axis in the netcdf file, I might
> get something more reasonable, but my question is:
>
> What is a good format to ex[press this to a GIS system?
>
> I'm imaging multiple files, maybe geo-tiff, but how to I express time and
> elevation in a way that is natural to GIS?
>
> thanks for your thoughts,
>
> -Chris
>
>
> --
> Christopher Barker, Ph.D.
> Oceanographer
>
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>
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