[GRASS-PSC] GRASS add-on sharing and write access

[Nagy Edmond]

Hi Anna,

Thank you for pointing that out. It always computes one way between two
points indeed, but there is something that I should bring to light.

While I was initially computing least-cost paths with r.drain using r.walk
outputs as inputs I noticed a possible problem. I ran two parallel tests
with the same two points. In the first one, A was the starting position,
while B the stop position. In the second one, B was the start point and A
the stop point. In r.walk, the results were anisotropic indeed, both the
walking cost and the movement direction raster outputs turned out different,
as it would have been expected. But the r.drain module sadly did not
generate different least-cost paths, despite using different inputs. I have
also checked this more than once, just to be sure of it.

At one point I have also come across an article (Gietl et al. 2008 - link
below) where the authors discuss and compare l.c.p. results obtained with
different GIS (including GRASS), and they had also experienced some problem
with the module (page 4), but I am not sure if it's the same I'm having. In
any case, if nothing can be done about it, then I will mention the
limitation in the documentation.

All the best,
Nagy Edmond

article -
http://proceedings.caaconference.org/paper/106_gietl_et_al_caa2007/



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