I'm a new user and just began with GRASS, where I learned to import 30x30 resolution ASTER files and then patch them (the six I'm working with) into one map. On QGIS, it doesn't appear that there's a similar function and all six tiles are kinda staggered regarding the color alignment. THen, how do you save the patched file and change the color schemes? Lastly, how to change the lat-long to UTM? And all this, from the same GeoTIFF file?


You can change the colortable on GRASS GIS itself using r.colors. Its very easy that way. Regarding conversion from latlon to UTM. you can enable On the Fly projection in QGIS project properties. You can find it in Options menu also. Just choose your UTM project and click Apply. You can now see the coordinates in meters when you move mouse over the map. To patch raster from QGIS you can install grass plugins for QGIS and run r.patch from there. If you dont want colortable assigned by GRASS. Run r.colors with -r option. It will remove any existing color table as per grass manual.

  • thanks, but how do you "patch" the tiles and change the color schemes on QGIS? – grad student Sep 27 '13 at 8:42
  • you didnt do it in GRASS GIS? .there is r.patch – rkm Sep 27 '13 at 8:57
  • no i wanted to assemble it all from QGIS application and the QGIS interface without having to go through GRASS at all. is this not possible? – grad student Sep 27 '13 at 9:22
  • you mean not using grass interface and using it through QGIS or doing in QGIS using GDAL. the latter i dont have any idea about patching but first one you can have qgis-grass plugins and do it from there. So you dont have to import data into grass location – rkm Sep 27 '13 at 9:47
  • this is helpful, thanks! the only issue left now is how to change colors in QGIS and get rid of the psychedelic ones from importing with GRASS. – grad student Sep 27 '13 at 10:28

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