I'm currently trying to do a viewshed (spatial analyst), using ArcGIS. The datasets being used are observation/observer points located WITHIN buildings, and a DSM of the surrounding area and the buildings.
To force the observation points inside the buildings, i have set the SPOT attribute to values lower than the buildings themselves (i.e. the observer is placed on the floor inside the building, instead of the roof).

Running this analysis is not possible, since it gives me the following error:

ERROR 010067: Error in executing grid expression. No valid Observation points present.

Reading through an answer from another thread on this website, the error occurs because the SPOT value is lower than the input DSM value in the same location (Error in viewshed (arcgis)).

I was wondering if there are any smart solutions/workarounds that mean i dont have to place the observers on top of the buildings?

  • Put him on a window side of a building at the window level
    – FelixIP
    Jul 12, 2017 at 10:25
  • 3
    My first idea would be to edit the DSM in such a way that the observer has nothing overhead? In that case the SPOT value would not be lower than the input DSM at that location.
    – LMB
    Jul 12, 2017 at 13:53
  • How does the observer see through the building ? is it full glass around ? does he move toward the nearest window? Do you have information about the structure of the building ?
    – radouxju
    Jul 13, 2017 at 7:34
  • @radouxju i assume the building is fully see through, due to limited information on building structure
    – Jonas
    Jul 13, 2017 at 8:09
  • @LaurensBakker This might be a smart solution; there might be a problem though: i need to work on several observers, so each time i remove a building's "top", i end up removing it from other observers' viewsheds (if that makes sense)
    – Jonas
    Jul 13, 2017 at 8:18

1 Answer 1


If the building is 'see-through' and you need the observer to be on the bottom floor, then that is the same as an observer standing on the ground where the building use to be, yes? If so, you need to edit your DSM before running the tool. Manually create a building footprint. Use zonal statistics (or manually figure out) the lowest elevation around the building. Attribute the footprint polygon with the lowest Z value. Convert the polygon to a raster using the lowest z value attribute. Replace the data in the DSM with the newly created raster using a Con function. Run the viewshed tool on this new surface.

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