[GRASS-dev] Ignored enhancements

[Hamish]

Doug wrote:
> I appreciate the effort.

(me too :)

>  Working with  large rasters, this will make a big difference! 

with respect to r.hozion, I'm still trying to understand where
the best use case for it is.

the idea as I understand it (which is not completely) is that
it precomutes some of what r.sun does, so that the r.sun module
runs faster. But the r.sun module places the sun exactly where
it wants it, while r.horizon must make some compromise and
approximate the position. to get any sort of reasonable placement
you'd need upwards of 100 seed maps, but since r.sun must open
them all at once the performance hit you take from the extra
overhead cancels out the speed gain. And so you have more disk
I/O with worse positioning -- better not to have used r.horizon
at all?

see further discussion and benchmarking in "r.sun2 commissioning
trials":
  http://trac.osgeo.org/grass/ticket/498

and on the r.sun page in the wiki:
  http://grasswiki.osgeo.org/wiki/R.sun#Seed_maps


thanks for any light you can shed on this, it has puzzled me
for a while.


Hamish