Hej,
thank you for your suggestions.
Chaitanya kumar CH schrieb:
Markus,
On Mon, Aug 24, 2009 at 10:06 PM, Markus Reinhold <
[email protected]> 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.
Well, I had been aware of gdal_translate, however I have to accomplish
my objective using the GDAL API. I'll have a look at source of
gdal_translate to see if there's something useful for me.
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
http://trac.osgeo.org/gdal/browser/trunk/gdal/frmts/raw/envidataset.cpp
Okay, that pretty much answers my questions. I created my own script to
add the map info line to the headerfile after copying the dataset. Since
my test data were in a pretty obscure projection and coordinate system,
GDAL didn't recognize it though. I'll adjust my script to avoid possible
conflicts with two map info entries.
Thanks again.
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: [email protected]
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