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On 08/14/2012 08:36 PM, Pedro Camargo wrote:
<blockquote
cite="mid:CAP=p+Yu2isqy=KKkj_BqjBn665ckr=LCtkv6_ARMdL+SqXUPrA@mail.gmail.com"
type="cite">Hi,<br>
I'm new to Grass and to Raster files, and although I know
some concepts, I'm having trouble to work with geotiff files.
Basically, I want to import tiff files downloaded from <a
moz-do-not-send="true"
href="http://nassgeodata.gmu.edu/CropScape/">http://nassgeodata.gmu.edu/CropScape/</a>
into vector layers.<br>
<br>
Any ideas on how can I do that?<br>
<br>
</blockquote>
<br>
I downloaded a small section of the 2011 landcover layer from the
site you linked to. In the download options, I specified WGS84
Lat/Lon coordinate system. (Otherwise is was projected in an
unknown, but specified Albers Equal Area CRS). Then I imported the
raster into a Lat/Lon WGS84 LOCATION in GRASS using: r.in.gdal. No
problem here:<br>
r.in.gdal in=NASS....tif out=nass <br>
# Or in the GUI, File->Import raster->Common import formats<br>
g.region -p rast=nass<br>
# Settings->Region->Set Region->Set to raster<br>
<br>
Next I did r.to.vect with the parameter "feature=area". This indeed
created a polygon vector map:<br>
r.to.vect in=nass out=nass feature=area<br>
# In the GUI, File->Map type conversions->Raster to vector<br>
<br>
However you need to be aware that the raster will be come many tens
of thousands of small polygons. I downloaded a small section of MA
and it was about 1000 columns X 500 rows. A 500,000 cell raster is
not large. But, converted to a vector this became 77,000 little
polygons. <br>
<br>
So the procedure works. The question is: Is that what you want?
What's your next step?<br>
<br>
<blockquote
cite="mid:CAP=p+Yu2isqy=KKkj_BqjBn665ckr=LCtkv6_ARMdL+SqXUPrA@mail.gmail.com"
type="cite">Thanks,<br>
Pedro<br>
<br>
<br>
PS - I'm using the GUI<br>
<br>
<br>
<br>
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</blockquote>
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