Problem creating viewshed raster in QGis - output black

Question

I am trying to do a viewshed analysis in QGis using the viewshed analysis plugin in QGis repository (https://hub.qgis.org/projects/viewshed/).

I had as base elevation contours in shp format with elevation data in ELEV (1).

which I converted to a raster DEM (raster > analysis > grid), creating a raster layer (elevation_raster) (2).

Then I created a new point layer (for the observer) in the same coordinate system as the elevation raster (3).

Finally, I tried to generate a viewshed analysis with the given plugin, defining the elevation raster, the observation point, search radius (5000), observer height (7000), target height (9000), trying to output a binary viewshed as raster with comulative option (4).

The result (viewshed_comulative) is just black, and I dont know where to find logs / debug this situation (5).

Tried in both QGis 2.10 and 2.12.

Answer 1

Found out the solution! First, I was wrongly considering absolute heights in observer/target height. Those are offsets. So I changed them to 1.6 / 0.

Then, turns out I needed to manually assign a projection to my DEM (raster > projection > assign projection).

Then it worked fine.