[Qgis-user] Projections of Landsat

[Micha Silver]

Roi Granot wrote:
> Hi Micha,
>
> Thanks for your answer.
>
> Can you please specify how I should implement your suggestions? I'm 
> new to QGIS and only used the GUI interface.
> Do you a execute a script in the unix terminal to do these?
>
Well you can, of course, run the commands from a terminal, but the GRASS 
plugin in QGIS gives a nice gui interface:
Once you activate the GRASS plugin, you'll see an additional toolbar. 
One of the icons if for creating a new mapset (and location). Using this 
wizard you'll want to make, as I mentioned, two locations. One - 
probably in some UTM zone - for the landsat images, and a second in the 
CRS of your GMT layers. You should be able to find the projection in the 
extensive list of projections offered by the wizard.

Next, click the icon to open the landsat UTM location, and then open the 
GRASS toolbox. All the GRASS modules are arranged in categories. So to 
import a tiff, look under File->Import->Import Raster. The r.in.gdal 
module  is the one needed.

Then use the r.null module which is found under Raster->Develop 
Map->Manage Raster Value. By setting the value '0' to null the black 
borders should disappear. Run this on each of the r-g-b bands of the 
original tiff. The you can merge them back into a full color raster with 
r.composite.  (under Manage Map Colors).
Finally, close the mapset/location and open the *other* mapset/location. 
Then run r.proj (under "Reproject raster from another location") and the 
landsat will be reprojected and warped to the CRS of the GMT layers.

Note that the user's manual, available on the QGIS download page:
http://download.osgeo.org/qgis/doc/manual/qgis-1.1.0_user_guide_en.pdf
can help alot in getting started. Even tho' the manual is for the 6 
months old version 1.1, it's still helpful. And the manual for 1.3 
should be available soon.

Good luck,
-- 
Micha
> Roi
>
> On Sep 18, 2009, at 6:57 AM, Micha Silver wrote:
>
>> Roi Granot wrote:
>>> Hi All,
>>>
>>> I'm loading Landsat raster image (.tif) and trying to combine it 
>>> with maps I created using GMT (.grd). What's the best way to do this?
>>> I tried to first change the Landsat projection to mercator (the 
>>> projection I used in GMT) - but the conversion didn't work fine.
>> You might find better results using GRASS for this. In general the 
>> steps would be:
>> 1- create two GRASS locations, one defined in the source CRS 
>> (matching the Landsat images) and a second in the target CRS,
>> 2- import the Landsat imagery into the first location with r.in.gdal.
>> 3- change to the target location and run r.proj to pull in and 
>> reproject the Landsat image bands.
>>> Also, how can I get rid of the black area surrounding the oblique 
>>> Landsat scene (which is filling the image where no data exist) so 
>>> that I'll be able to see the background?
>> Again with GRASS
>> 4- use the r.null model setting the '0' values (black) to NULL. 
>> Worked for me...
>> 5- and finally merge the bands back together with r.composite, and 
>> export back out to a tiff with r.out.tiff
>> All the above can be done with the GRASS plugin from within QGIS.
>> -- 
>> Micha
>>>
>>> Many questions indeed!
>>>
>>> Thanks,
>>> Roi
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>>
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