I am new to qgis and trying to do 2 things. My objective is to have an accurate viewshed analysis at the end. But my DEM file is of poor resolution.

I do have a shapefile with building height details. I am trying to (Part1) find a way to make a new DEM with building heights and (Part 2) calculate the viewshed from certain buildings from the created DEM. (Part3)At a later stage, want to be able to tell from which buildings is a certain polygon on the ground visible.

Does anyone know how to do this?

closed as too broad by ahmadhanb, Jochen Schwarze, whyzar, Mark Ireland, csk Jan 28 at 18:55

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  • Please include in your question what you have tried so far and where you are stuck. – Stefan Jan 28 at 9:24
  • I had a very low-res DEM file which I tried to use for creating the viewshed but couldn't do that. I calculated the building heights for my shapefile by adding a new field and multiplying the no. of floors with an average floor height. I'm now wondering how to use these building heights to create a DEM. – Manasvini Hariharan Jan 28 at 9:30
  • If you want to modify your DEM with the building heights from the vector layer, try searching for burning a vector into a raster. I'm sure it's been explained somewhere on the internet for your chosen GIS software. – csk Jan 28 at 18:55

Some solution elements. The simplest way to make some viewshed analysis is to use the viewshed analysis plugin (https://plugins.qgis.org/plugins/ViewshedAnalysis/). It allows to calculate viewshed from a raster and a point.

You can try this method :

1/ To get a DEM with buildings height : You can calculate the height of the buildings and rasterize them and add this height raster to your DEM with the raster calculator

2/ Transform your buildings into points : by taking the centroid of each building, the buildings points or a sampling of points inside the building (choose the most adapted method according to your problem)

3/ Calculate the viewshed with viewshed analysis plugin. According to your building transformation into point, you have to merge some viewhed polygons.

  • Thanks Mickael. I'm trying to make the DEM with buildings height. I'm wondering how to rasterize the height of my buildings? Is it necessary to add the height raster to my existing DEM or can I just use the buildings raster for the viewshed? – Manasvini Hariharan Jan 29 at 1:22
  • For the rasterization > Raster > Conversion > Rasterize. If your terrain is very flat you can ignore it, if not you should use it – Mickaël Brasebin Jan 29 at 8:19

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