[GRASSLIST:651] Re: Shortest distance routing

[Buchan Milne]

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Alexander Pucher wrote:
> Hi, just a quick question,
>
> can somebody point me to some information on how to work with network
> (esp. road network) analysis in GRASS. Let's consider I have a vector
> databases of a city's road network and want to find out the shortest
> distance between point A and B.
> All I can find by looking at the docs and searching through google are
> more or less surface runoff routing examples.
>

You need grass51 (from cvs), which has the dglib library and some tools
that use it, such as d.path.

http://mpa.itc.it/radim/g51/d.path.jpg

I am using this kind of functionality (I can't discuss the big picture
behind it on the list, but maybe in private), and have been working on
modifying d.path (renamed to v.path) to be a bit more friendly for my
purposes (I would like to extract information on the actual segments,
which d.path does not do, just displays it in the monitor), with a flag
to display the results on the monitor (to check results).

At present, d.path allows you to click on the monitor to select start
and end, my v.path takes an unlimited number of coordinate pairs as an
argument, and will make find the shortest path that goes through the
points in order (ie not a travelling salesman problem, which would
re-arrange the order).

I haven't finalised all the interfaces for v.path, so it may be possible
for me to adjust it to suit what others would like from it.

Regards,
Buchan

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Buchan Milne                Mechanical Engineer, Network Manager
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