Oops! I've made another tentative, I've used r.mask to mask out the area within the start polygon, but surprisingly I got the same result, as it seems that the mask does not affect the result at all. IMHO this could be a bug of r.mask (ok, separate topic), or is there any reason why r.mask shouldn't affect it?
Thanks On Wed, Dec 19, 2012 at 3:25 PM, Margherita Di Leo <[email protected]>wrote: > Hi All, > > I have a friction map, a start polygon and an end polygon and would like > to find the least cost path, meaning not a corridor but a thin line. To now > I've tried both r.cost and r.walk and r.drain eventually, but the result of > this latter > > r.drain input=friction@PERMANENT output=rdrain_out > vector_points=start_line@PERMANENT > > is a path calculated *within* the start polygon (a closed line). > I suppose this is because I don't provide a direction map to r.drain (I'm > using GRASS 7). I read: > > If the *input* surface (a raster map layer) is a cumulative cost map > generated by the *r.walk<http://grass.osgeo.org/grass70/manuals/r.walk.html> > * or *r.cost <http://grass.osgeo.org/grass70/manuals/r.cost.html>* modules, > the -d flag and a movement direction surface *"indir" *must be specified. > > I assume it's a kind of flow direction or aspect, but what is the physical > meaning, and how can I calculate it? Could anyone please provide some > further info. > > Thank you in advance > > Madi > > > -- > Margherita DI LEO > Postdoctoral Researcher > > European Commission - DG JRC > Institute for Environment and Sustainability (IES). Unit H03 – FRC > Via Fermi, 2749 > I-21027 Ispra (VA) - Italy - TP 261 > > Tel. +39 0332 78 3600 > [email protected] > > Disclaimer: The views expressed are purely those of the writer and may not > in any circumstance be regarded as stating an official position of the > European Commission. > -- Margherita DI LEO Postdoctoral Researcher European Commission - DG JRC Institute for Environment and Sustainability (IES). Unit H03 – FRC Via Fermi, 2749 I-21027 Ispra (VA) - Italy - TP 261 Tel. +39 0332 78 3600 [email protected] Disclaimer: The views expressed are purely those of the writer and may not in any circumstance be regarded as stating an official position of the European Commission.
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