[GRASS-user] r.terraflow for cost path analysis

[Hamish]

Colin wrote:
> A recent article published in the
> Journal of Archaeological Science
> (http://dx.doi.org/10.1016/j.jas.2010.11.006) proposed a
> method where
> hydrology models could be used on the product of a cost
> surface
> analysis to create a network of paths (instead of just the
> one made
> with r.drain -d). The flow accumulation map would represent
> the number
> of cells in the map from which a least-cost path would pass
> through
> that cell. ie. a flow accumulation of 100 means that 100
> cells would
> have a LCP that would pass through that cell. You could
> also calculate mobility basins (like a watershed), etc.
> 
> This is great extension of cost surface analysis except
> that I don't
> think it can be done in GRASS right now. r.cost and r.walk
> produce a cumulative cost surface and a "flow" direction
> surface, but if I'm
> right r.terraflow can't take them as inputs because it
> calculates everything "in-house".
> 
> I was hoping someone could double-check my logic on this or
> perhaps
> suggest an alternative hydrology module(s) which could take the
> direction surface as an input instead of calculating
> everything from the elevation surface.


(sorry about yahoo's lame line wrap)

not exactly the same thing, but you might check out v.surf.icw
from wiki-addons:
  http://grass.osgeo.org/wiki/AddOns#v.surf.icw

v.surf.icw is an IDW interpolation method using true distance cost instead of euclidean shortest distance, i.e. as the fish swims around an island not as the bird flies. This will cleanly travel around hard barriers and a cost surface map may be used to model expensive-cross barriers. Input data points do not need direct line of sight to be considered, but should be kept to less than one hundred as the module becomes very computationally expensive. A number of radial basis function options are available. 
screenshot:
 http://grass.osgeo.org/grass-wiki/images/Inlets_03_SurfSal_icw_big.png



maybe it helps,
Hamish