QGIS Lab10 Fall14: QGIS Raster Analysis

Introduction:

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. Use full screen for clear content of video. The download link of below video is ogg video or mp4 video. You can play it in vlc player or open it in web browser.

The example files that are used in video can be downloaded from here .

Reference:

  1. Chapter 08 of QGIS 2.6 Training Manual