[GRASS-dev] Re: v.net.path

[Hamish]

> > > v.net.path:
> > > "Shortest path from two digitized nodes" example
> > > also try:
> > >   d.path -b roads coor="601653.5,4922869.2","593330.8,4924096.6"
> > > and
> > >   d.path -b myroads_net
> > >   coor="601653.5,4922869.2","593330.8,4924096.6" \
> >            afcol=forward hcolor=green
> > 
> > How cool, I didn't realize this -b flag so far.

I just added it recently, same time as coor=.
  (coor= so we can use d.path from the GUI)

> > The difference is striking. I am not really sure about the second
> > one.
> 
> OK, my mistake - the column should contain *costs*. That might be
> the inverse of the speed limit, not the speed limit itself:
> e.g.
> # define traveling costs as inverse of speed limit:
> v.db.update myroads col=forward val=1/50

ahh. Is "backward" really needed? (is it optional in d.path) I'm not
really sure what that means actually. Does it mean it costs more to
drive the wrong direction on a one way street? Harder to canoe upsteam?

> I have update the example in CVS. Please suggest if you have better
> ideas.

For completeness: re speed limits- Expect 30mph on residential streets,
55mph on minor highways and up to 75mph on the interstate. This varies
state to state & I'm not sure what the rules are in the Dakotas, but I
expect they let you go pretty damn fast. :)

but google knows all:
 http://www.iihs.org/laws/state_laws/speed_limit_laws.html



Hamish