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<div class="moz-cite-prefix">Hi Thomas,<br>
<br>
regarding the size of the graph I don't expect problems, as the
world wide OSM graph currently has over 83mio nodes.<br>
<br>
The problem is the algorithm and if it scales. E.g. if I would use
a normal bidirectional dijkstra for a 10 000km query it would take
over 10 seconds but with a short cutting or hierarchical algorithm
like contraction hierarchies it is under 100ms! So I'm really
excited to hear what you choose for an algorithm :) !<br>
<br>
Regards,<br>
Peter.<br>
<br>
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<div class="moz-cite-prefix">Thank you for your response and
offering your help.<br>
<br>
I have looked little bit into the thematic and it seems that a
implementation with a time-expended graph would be very straight
forward. So, I would have to implement a GTFSReader which
creates the public transport graph.<br>
Would this approach perform well with ~1 million nodes (time
stops)?<br>
<br>
Regards,<br>
Thomas<br>
<br>
<br>
<br>
On 04/08/2013 09:09 PM, Peter K wrote:<br>
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Hi Thomas,<br>
<br>
public transport would be nice to have, yes :) <br>
<br>
But there is no time dependent datastructure yet, and the
algorithms are not tuned regarding public transport. So, it is
not easy to implement. If you do not have much data you can just
use the GraphStorage (and model the time via nodes), then use
a-star or dijkstra to get routes. One minor gimmick would be the
'wayGeometry' (in EdgeIterator) which you could use to display
the real paths between two nodes of the trains/buses/... instead
of straight line like e.g. google does. <br>
<br>
To properly implement public transport one would probably need
to create a new Graph interface and iterate from that, e.g.
create a simple algorithm and then use more advanced like
RAPTOR. Also a new GTFSReader will be necessary instead of or
combined with OSMReader. <br>
<br>
If you're trying something you can be sure to have my assistance
:) ! <br>
<br>
Regards, <br>
Peter.<br>
<br>
------------------------------------------------------------<br>
<br>
Hello, <br>
<br>
I'm considering to use graphhopper for a student project. But
for that I <br>
also need support for public transport. So I'm thinking about <br>
implementing it my own... <br>
Do you have any thoughts or plans how to implement it and would
it be a <br>
lot of work? <br>
<br>
Regards, <br>
Thomas <br>
<br>
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