[OSRM-talk] new api table and geometry

Michal Palenik michal.palenik at freemap.sk
Fri Apr 15 20:27:40 UTC 2016


daniel, 

thanks for the explanations.

my need to calculate (and show) only 1x15 matrix blurred my vision of
all the problems :)

what I try to achieve is multimodal routing (foot+bus+foot) by showing
three geometries combined into one (plus some instructions).

michal

On Fri, Apr 15, 2016 at 12:56:20PM -0700, Daniel Patterson wrote:
> Michal,
> 
>   Strangely enough, we don't actually have the geometry.  We find a path across the Contraction Heirachy
>   routing graph, this may only have a small handful of edges.  We can sum these edges to get the route
>   duration, but to get the actual geometry or distance, we then have to "unpack" those edges.
> 
>   The table plugin doesn't do this unpacking step.  It gets the durations easily, but would be significantly slower
>   if we also had to report back the route geometries.  The API response would probably also be huge (10s or 100's of MB?) for any
>   non-trivial number of route pairs in the table.  To support that, we would need a way to stream the response
>   asynchronously to the HTTP client, otherwise a couple of requests could use up all the RAM on the server.
> 
>   Things are never as simple as they seem :-(
> 
> daniel
> 
> > On Apr 15, 2016, at 12:45 PM, Michal Palenik <michal.palenik at freemap.sk> wrote:
> > 
> > that is what I already do, but it means a lot of (unnecessary)
> > connections. I assume the geometries are already available when
> > computing the duration. 
> > 
> > I was hoping for a "documentation lacking behind development"
> > scenario... 
> > 
> > 
> > cheers, 
> > michal
> > 
> > On Fri, Apr 15, 2016 at 04:09:49PM +0200, Daniel Hofmann wrote:
> >> If you check the v5 spec you linked, you will see only Route, Trip and
> >> Match providing a "geometries" option.
> >> 
> >> What you can do is this:
> >> - do a Table request from your position against all Bus / Tram stops in the
> >> area / in a buffer of a few kilometers
> >> - pick n shortest routes from the Table response and temporarily store
> >> their destination coordinates
> >> - do n Route request from your position against the n destination
> >> coordinates and extract the geometry
> >> 
> >> Cheers,
> >> Daniel J H
> >> 
> >> On Fri, Apr 15, 2016 at 3:49 PM, Michal Palenik <michal.palenik at freemap.sk>
> >> wrote:
> >> 
> >>> hi,
> >>> 
> >>> within the new api, I am trying to find how to get geometry (together
> >>> with perfect duration). is it possible?
> >>> 
> >>> or do I have to make N*M queries for all the possible combinations?
> >>> 
> >>> 
> >>> https://github.com/Project-OSRM/osrm-backend/wiki/New-Server-api#service-table
> >>> 
> >>> I am trying to make a service like "show me the routes to the closest
> >>> bus/tram stops" : http://epsilon.sk/mhd/
> >>> 
> >>> thanks
> >>> 
> >>> michal
> >>> 
> >>> --
> >>> michal palenik
> >>> www.freemap.sk
> >>> www.oma.sk
> >>> 
> >>> 
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> >>> 
> > 
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> > 
> > -- 
> > michal palenik
> > www.freemap.sk
> > www.oma.sk
> > 
> > 
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-- 
michal palenik
www.freemap.sk
www.oma.sk




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