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Highest level curve per (Voronoi) polygon?


I am facing a difficulty in QGIS (2.8.2): I have three layers:

  • layer 1: layer with points
  • layer 2: layer of level curves (contour lines)
  • layer 3: layer of Voronoi polygons obtained from the points layer (layer 1).

What I need to get is, for each point (layer 1), the highest elevation contained in its respective Voronoi polygon.

How could it be done?


The easiest way is to use a raster elevation dataset. If you can't get hold of the one used to create the contours (presuming they weren't done by hand from point data) you can:

  • Open menu Raster/Conversion/Rasterize (Vector to Raster)
  • Choose your contour (level curves) file and a suitable grid size (likely based on the area you wish to work with and contour resolution)
  • Press OK.

You can then sample the resulting raster for the Voronoi polygons:

  • Make sure you have the 'Zonal Statistics' plugin activated
  • Select your voronoi polygon layer for zones
  • State the column prefix you want for the new columns
  • Choose what you want reporting
  • Press OK.

From here you need to join the point and voronoi layer, either by attribute or location.