[SoC] GRASS - Network Analysis - report

Daniel Bundala bundala at gmail.com
Fri Jul 17 18:00:25 EDT 2009

Hello all,

I worked on the module similar to v.net.path this week. The difference
is that my module uses timetables to find the fastest path between two
stops at/after the given time. The timetables are stored in an
attribute table. For each route, the table contains the stops and
times. Also, walking connections between the stops can be specified in
a different table. Routing is done according to several options. Apart
from the obvious ones such as: "from stop", "to stop" and "time",
other options are: maximum number of changes (this can be any non
negative integer or infinity), minimum time required for a change and
whether walking is considered as a change (this is important when
maximum number of changes is finite). Using these options, the modules
finds the fastest path and produces textual output in the form (this
is still only temporary and the output will likely change to something
easier to process):

Route 5, from 100 leaving at 0 arriving to 130 at 10
Route 15, from 130 leaving at 15 arriving to 250 at 22
Walk from 250 leaving at 22 arriving to 300 at 24

And produces the following output map:
http://people.ksp.sk/~dano/grass/tt.png. Where Route x, is the
identificator of a route and from y to z are identificators/categories
of stops.

In the tradition of v.net.path, the module reads data from the
standard input, so the map may contain more than one single path.

For the next week, I plan some changes to the module. Especially, I
want to improve the output, possibly outputting to an attribute table.
Also, a nice feature of v.net.path is that it can take two coordinate
points and finds the shortest path between the nodes in the network
closest to these points. I think it would be nice to have something
like this in this module.


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