Marking Slopes

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  1. Now we'll use GIS information to create more informative maps. For refugee camp, we need flat land to build camp or tent. The slope information in degrees mesurement from the map can be used to presenting a visualization where's the best place to build refugee camp or where's the part of the island which is not suitable for encampment.
  2. Open grass, select "mentawai_2" location and our mapset ("fossgiss" or "instruktur")
  3. Press the "Add Raster Layer" icon (Step 1), select the layer (Step 2), browse the map (Step 3), select our latest map that has been cropped to "srtm_mentawai3" (Step 4)
    Image:Screenshot9.png
  4. Switch to "Map Display" window, press the "Display Active Layer" icon on the upper icon bar
    Image:Screenshot-Map Display 1-99.png
  5. Access menu Raster > Terrains Analysis > Slope and Aspect
    Image:Screenshot-GRASS6.2.2 GIS Manager - mentawai 2 instruktur-2slope.png
  6. Select the map source ("srtm_mentawai3") and create output map name ("srtm_mentawai3_slope"). Set the measurement ("degrees") and data type ("integer"). Press "Run" to begin converting
    Image:Screenshot-r.slope.aspect-1.png
  7. Click "Add Raster Layer" icon, add map "srtm_mentawai3_slope", click "Display Active Layer" on display map window
    Image:Mulai ngantuk euy.png
  8. Now we'll classifiying the slope's degrees. We'll divide the slopes into three level:
    * 0˚ - 10˚ sloppiness (Good for camp)
    * 11˚ - 30˚ sloppiness (Too slope)
    * 31˚ - 54˚ sloppiness (Not suitable)
  9. Access menu Raster > Change Category Values and Labels > Reclassify Using Files , we'll describe the above slopiness definition to one text file that will be used by GRASS.
    $> gedit /home/username/maps/slope_definition.txt
    It's content is:
    0 thru 10 = 1 0˚ - 10˚ sloppiness
    11 thru 30 = 2 11˚ - 30˚ sloppiness
    31 thru 54 = 3 31˚ - 54˚ sloppiness
  10. Set the map source name "srtm_mentawai3_slope", the output map name "srtm_mentawai3_slope_reclassified" and define where is our text file definition ("/home/username/maps/slope_definition.txt"). Press "Run"
    Image:Screenshot-r.reclass.file.png
  11. Click "Add Raster Layer" icon, add map "srtm_mentawai3_slope_reclassified", click "Display Active Layer" on display map window
    Image:Wangi jeruk ih.png
  12. We can add map legend by clicking "Add Raster Legend Layer", setting map source ("srtm_mentawai3_slope_reclassified") and adjust some text size ("5,20,5,10")
    Image:Seperti lampu merah yaaah.png
  13. Click "Display Active Layer" on display map window
    Image:Secara warnanya kuning.png
  14. To get more informative color legend we can redifine the color tables using menu: Raster > Manage Map Colors > Set Color Using Color Rules. Add map "srtm_mentawai3_slope_reclassified" as map source, press "Run" then insert this console based information:
    Image:Mulai panas punggungnya.png
  15. Greeny land will be suitable for encampment ^^
    Image:Horeee ijoooo.png


On to Next Step: Converting to Vector

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