[GRASS5] [bug #2061] (grass) r.los needs FP update

[Paul Kelly]

On Wed, 13 Aug 2003, Request Tracker wrote:

> this bug's URL: http://intevation.de/rt/webrt?serial_num=2061
> -------------------------------------------------------------------------
>
> Subject: r.los needs FP update

It is my idea for a sort of long-term plan / project that I would like to
re-write r.los, based on an algorithm that was published in the July issue
this year of 'Photogrammetric Engineering & Remote Sensing':
http://www.asprs.org/asprs/publications/pe&rs/2003journal/july/abstracts.html
The title is 'A Fast Algorithm for Approximate Viewshed Computation'
The improvements in r.cva (cumulative viewshed analysis
http://www.ucl.ac.uk/~tcrnmar/GIS/r.cva.html ) would also be incorporated
into this new version. (r.cva also does not work with floating point maps
although it is well written and up-to-date and is a lot better than the
current r.los; the web page doesn't seem to have any information on the
licence though so it is unclear if it can go into the current GRASS)
Anyway the functionality can just be cloned anyway; it would probably be
easier to do this than adapt seeing it is based on the old r.los.

The algorithm in PE&RS is from the US Army CERL so it would be especially
appropriate for it to go into the latest GRASS. I would hope some of the
Vectlib and dglib functions could be used for determining the crossing
points and distances between the cells but I will have to learn about
them first.

Paul