[gdal-dev] Extracting band from raster stack & ENVI Header question

Chaitanya kumar CH chaitanya.ch at gmail.com
Tue Aug 25 03:45:20 EDT 2009


On Mon, Aug 24, 2009 at 10:06 PM, Markus Reinhold <
markus.reinhold at uni-jena.de> wrote:

> Hejhej,
> please allow me two short questions:
> 1) Using the GDAL Python bindings I currently need to extract a single band
> from a raster stack and save it in a different format, i.e. ENVI. To achieve
> this my processing includes
> (a) analysis of the source dataset and desired band (width, height, pixel
> size, data type, geotransform),
> (b) creation of a temporary in-memory dataset with one band (using
> Driver.Create()) that is identical with the desired source band except that
> it is all black and
> (c) creation of a copy of the temporary dataset (using Driver.CreateCopy())
> and setting it according to the original data (using
> RasterBand.ReadAsArray() and RasterBand.WriteArray()).
> I found the second step necessary as for ENVI data it is only possible to
> create datasets using Driver.CreateCopy() for which a template is needed -
> hence the temporary single band dataset... My solution works, I find it a
> bit awkward though. Is there a simpler way to do this?

I am not sure what all you are trying to do here but the utility program
'gdal_translate' (http://gdal.org/gdal_utilities.html) may help you. There
are some other programs described in that page.

> 2) Another question concerning the creation of ENVI datasets with GDAL. I
> had been under the impression that *map info* strings for the ENVI header
> weren't created when copying another dataset. Now I have found that when the
> dataset is in a certain projection and coordinate system, i.e. UTM/WGS84 in
> my case, this is done after all. Is there any rule for which configurations
> GDAL is able to create a *map info*-section in the ENVI header?

I don't know much about the ENVI driver but a glance at the source code
shows that 'map info' is hard-coded. You can take a look at the current
development snapshot at

> Thank you very much in advance.
> Regards,
> Markus
> --
> ********************************************************
> Dipl.-Kartograph Markus Reinhold
> Chair of Geoinformatics, Geohydrology and Modeling
> Friedrich-Schiller-University Jena
> Löbdergraben 32
> D - 07743 Jena
> Germany
> Phone.: (+49)(0)3641 / 9 488 65
> E-Mail: markus.reinhold at uni-jena.de
> ********************************************************
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Best regards,
Chaitanya kumar CH.
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