[GRASS-user] how to measure distances in a constrained space

[Hamish]

Moritz:
> Well the above works, i.e. just setting obstacles to NULL
> in the cost map. Obviously this only works if obstacles
> represent total barriers, not just increased friction.


if cost map is all "1" and you multiply by map resolution later to get
distance, then you could simulate increased friction by having some cost
cells as 2,3,4, etc... twice as slow is effectively twice as far.

I am working in waterways, I have wondered about generating an upstream/
downstream cost map to use with v.surf.icw so interpolation following
river bends prefers not to mix pollutants/invasive species from tributaries
upstream as readily as downstream... ie make it more expensive to move
upstream, but not impossible (tidal exchange, diffusion, turbulence, etc).
That module does not care about absolute distance, just that all use the
same method.


Hamish