[GRASS-user] calculate height above ground for a specific vertical angle of view

[Frank David]

Hello,

I have calculated viewshed maps from one point of view at 2m height 
increasing the altitude above topography from 0 to 250m. So with 
r.series i can calculate the total visible height (sum of True in meter) 
or the total invisible height(sum of false in meter), or the vertical 
visible angle (angle-mode).

I want now calculate the visible height (in metres) according to a 
specific vertical angle of view from my point of view.

Witch method I could use to get effectively that result ?

Thanks !