QGIS Raster Analysis

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This is tenth video tutorial of QGIS. It is about raster analysis. The objective is to learn and use raster analysis in qgis.

Summary:

  1. Load analysis.qgs
  2. Set project crs to 33S
  3. Add four settelite files and create virtual raster catalog. Raster > Miscellaneous > Build Virtual Raster (Catalog).
  4. Save in exercise_data/residential_development as aerial_photos.vrt
  5. Raster > Projections > Warp (Reproject). to 70300
  6. Raster > Miscellaneous > Merge.
  7. Changing Raster Layer Symbology and using View > Toolbars > Raster
  8. Terrain Analysis (hillshade, Slope and Aspect)
  9. Using the Raster Calculator, aspect@1 <= 90 OR aspect@1 >= 270, save it in aspect_north.tif and also calculate slope_lte2.tif and slope_lte5.tif.
  10. Write criteria for location: ( aspect_north@1 = 1 AND slope_lte5@1 = 1 ) OR slope_lte2@1 = 1 and save it as all_conditions.tif.
  11. Simplifying Raster: all_conditions_sieve.tif and Threshold and Pixel connections values to 8
  12. Open the Raster Calculator again, and build this expression: (all_conditions_sieve@1 <= 0) = 0 and save output as: all_conditions_simple.tif
  13. Raster > Conversion > Polygonize (Raster to Vector). Field name = suitable and save it as: all_terrain.shp
  14. For filer of suitable = 1, save it as suitable_terrain.shp
  15. Raster > Conversion > Rasterize (Vector to Raster) for suitable_terrain.shp, width = 837 and height = 661
  16. Use the Intersect tool (Vector -> Geoprocessing Tools) to create a new vector layer called new_solution.shp which contains only those buildings which intersect the suitable_terrain layer.

Below is the full video lecture including model files. 

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Code

QGIS Raster Analysis
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