[Gvsig_english] Visibility analysis

[Antonio Falciano]

Il 24/09/2013 13:26, Angus Jeffery ha scritto:
> Hi Antonio
> Thanks for your reply. Very interesting despite my lack of Italian and I
> can see some application for your research.
> However, it's not quite what I meant - what I want to try to do is work
> out which part of a defined site (I have a polygon) is least (or most)
> visible from the surrounding landscape within a defined radius (I have
> raster of elevation data). Any ideas?

Hi Angus,
I'd convert the polygon into a set of equispaced points using e.g. the
SEXTANTE "Create graticule" tool (to be clipped). The distance to adopt
should be the DEM cell size. Each point can be considered as a single
target and then be used for the computation of a binary viewshed in
order to understand from where it's visible within the search radius.
The number of pixels of the binary viewshed whose value is equal to 1
(i.e. the sum of all the values within the search radius) will represent
the score of each point. Higher is the score, more visible from
different places the point will be. It could be calculated with the
SEXTANTE "Basic statistics" tool.
The complex part is that we have to iterate over all the points and for
sure the best approach is to do it programmatically, e.g. with some
BeanShell scripting under SEXTANTE or Bash/Python under GRASS GIS.

Cheers,
Antonio

-- 
Antonio Falciano
http://www.linkedin.com/in/antoniofalciano