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"PETER.HAKIM" wrote:
>
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> Dear Idrisians
> I have downloaded the GOTOPO30 tile for the Indian subcontinent.
> The data is in 16 bit signed integer format, and on attempting to convert
> it to idrisi format using the demidris module, an error message : "Unable
> to read as integer value" is flashed.
> The dem file can be displayed directly in idrisi by just changing the
> .dem extension to .img., but the values are altered i.e. the max and min
> pixel values (elevation values) are totally different.
>
> Has any one found a way to import the GOTOPO30 dem file with the values
> intact to IDRISI ?
> please help
>
> Thank you
> Dr. Hrishikesh P. Samant
> Dept. of Geology
> St. Xavier's College
> Mumbai, 400 001
> INDIA
>
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I imported the DEM file (*.dem) into IDRISI using the Band Interleaved
by Line (BILIDRIS) module. The parameters I used are specified in the
README.html file which is at the web site. However, for an example,
the file W100N90.DEM uses the following parameters:
input file name: w100n90.dem (or your DEM filename for your zone)
output file name: test
number of bands: 1
no header
16 bit UNIX/Motorola
number of columns per band: 4800
number of rows per band: 6000
minimum x: -100 (or your min long)
maximum x: -60 (or your max long)
minimum y: 40 (or your min lat)
maximum y: 90 (or your max lat)
reference system: Lat/Long
reference units: degrees
value units: kilometers
unit distance: 1
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This creates an test.img and test.doc file which is in IDRISI format,
and you can view the data and do everything else that one does in
IDRISI to the data.
This is the location of the GTOPO30 free data as well as the README.HTML
file:
http://edcwww.cr.usgs.gov/landdaac/gtopo30/gtopo30.html
Hope you get it to work,
Stan
P.S. - visit my web page for some great GIS sample images and a long
list of GIS/RS web sites and other sites:
http://home.istar.ca/~climber
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