On 11/13/2015 6:00 AM, Pedro wrote:
Hi there,
I'm trying to solve a common problem which is railway routing, thus
enforcing some turn restrictions that may never happen in a
pedestrian/car network.
Trains cannot do sharp turns, so what I have now is a list of source and
target edges that i dont want to occur on my shortest path. The problem
is that the way pgr_trsp works right now with weighted restrictions is
not good for me because those turns cannot happen, not based on their
weights but by the simple fact that it is impossible for a train to
maneuver like that under normal conditions and speed.
My question is, is there the possibility of ignoring the weight and just
to check if the turn is allowed or not ? Am I missing something on the
documentation that specifies that ? Setting the weight to some specific
vale perhaps ?
I'm not sure if that is implemented. Try setting the cost to -1 and see if that works.
Otherwise all you can do is set the cost to a really high number which will force it to find a lower cost alternative route. Then you will need to check the results and if the high cost turn was included then you need to realize that the requested route is not possible without taking an impossible turn, so treat that as no route was found.
-Steve
There is a wiki about this kind of problem here:
https://github.com/pgRouting/pgrouting/wiki/TRSP-for-railroads
but I think it has some issues:
https://github.com/pgRouting/pgrouting/issues/286
https://github.com/pgRouting/pgrouting/issues/288
One of them is because contradictory input (or maybe both)
I have comments about it there.
I suggest you read all three links (maybe try the simple example).
and instead of negatives give a big number as cost.
Vicky
To: pgrouting-users@lists.osgeo.org
From: woodbri@swoodbridge.com
Date: Sat, 14 Nov 2015 10:54:26 -0500
Subject: Re: [pgrouting-users] pgr_trsp - applying restrictions with no consideration to their cost
On 11/13/2015 6:00 AM, Pedro wrote:
Hi there,
I’m trying to solve a common problem which is railway routing, thus
enforcing some turn restrictions that may never happen in a
pedestrian/car network.
Trains cannot do sharp turns, so what I have now is a list of source and
target edges that i dont want to occur on my shortest path. The problem
is that the way pgr_trsp works right now with weighted restrictions is
not good for me because those turns cannot happen, not based on their
weights but by the simple fact that it is impossible for a train to
maneuver like that under normal conditions and speed.
My question is, is there the possibility of ignoring the weight and just
to check if the turn is allowed or not ? Am I missing something on the
documentation that specifies that ? Setting the weight to some specific
vale perhaps ?
I’m not sure if that is implemented. Try setting the cost to -1 and see
if that works.
Otherwise all you can do is set the cost to a really high number which
will force it to find a lower cost alternative route. Then you will need
to check the results and if the high cost turn was included then you
need to realize that the requested route is not possible without taking
an impossible turn, so treat that as no route was found.
-Steve
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