[R-sig-Geo] summing up the highest Raster values within polygons

[didimayr]

Dear all,

I have a little bit complex problem and don't know how to start solving it.
Maybe someone has experience with similar issues or knows a solution.

1) I have many Raster files with (solar-)energy-Values, based on a digital
elevation model (DEM). Depending on the orientation and the slope of cell,
the raster represents the applicability of this field to install a
photovoltaic modul. 
2) Furthermore I have polygons representing the shape of houses (=roof)
lying in the same (raster) area. So the solar-values of the Raster indicate,
if the house well orientated for a solar module. 

Now I first have to cut the raster with the polygons, in order to analyze
only the roof areas (which are in my interest).
Then comes the main problem: I want to know the energy-value on each roof
(=within each polygon), however it should not only be the sum of the whole
roof, because solarmodules are only situated on the best sites of the roof.
Thus I need to identify a "cluster" or "window" of the highest cell-values
within the polygon, which I want to sum up. If necessary I could define the
size of this window/cluster.

 
It seems to me that I have to work with a focal function or by using RSAGA:
multi.focal.function.
are there other possible approaches and has anyone done a similar analyzis?

Thanks a lot and kind regards
Dieter Mayr







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