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I am using QGIS 2.18.19 to produce viewsheds of a proposed development to show where the development would in theory be visible from. I am using Ordnance Survey Terrain 5 as my height data (*.asc) which I have loaded and saved out as a GeoTIFF so that it is correctly geo-referenced to the coordinate reference system I am using (OSGB36).

At present I have run a viewshed of the development using the DTM which gives the theoretical visibility as if the earth was bare. I have a separate vector dataset of woodland which I have converted to a raster.

Firstly, how can I add give the woodland raster a notional height so that each block of woodland has a height of 10m?

Secondly, how do I add the raster of the woodland (with notional woodland height) to the DTM so that I have a raster of the DTM with woodland heights?

  • Not a duplicate, but it basically works like this: gis.stackexchange.com/a/307648/107424. Just use your woodlands polygon instead. – MrXsquared Feb 8 at 15:30
  • Thanks - followed that tutorial through trying it using Raster - Conversion - Polygon to Raster and also using Rasterize (Vector to Raster) via processing toolbox and the Raster conversion way worked perfectly!! – DavidG Feb 8 at 16:50
  • @DavidG If you write that up as an answer to your own question it will help other people who come to this site. – csk Feb 8 at 17:42
  • Just a thought but have you had a look at what DTMs and DSMs if any are available from the EA for your area of interest? The DTMs are bare-earth models and the DSMs include surface vegetation and buildings. See: ckan.publishing.service.gov.uk/publisher/… and ckan.publishing.service.gov.uk/publisher/… – nhopton Feb 10 at 9:27
  • Thanks - yes I have looked at the EA's DSMs although coverage is patchy in my area of interest – DavidG Feb 14 at 16:40

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