[OSRM-talk] "nearest suitable road segment" Was: Helgoland in St. Peter-Ording

Michal Palenik michal.palenik at freemap.sk
Wed Sep 28 08:16:23 UTC 2016


FYI, I've added a feature request to nominatim
https://github.com/twain47/Nominatim/issues/536

michal
On Wed, Aug 17, 2016 at 11:00:27PM +0200, Florian Lohoff wrote:
> On Wed, Aug 17, 2016 at 01:26:44PM -0700, Daniel Patterson wrote:
> > Hi Florian,
> > 
> >   This sounds like more of a geocoding problem than a routing problem.
> >   OSRM itself doesn't know anything about addresses, it only works
> >   with coordinates and road geometry.  All OSRM has internally are
> >   street names, not street numbers or place names.
> > 
> >   In order to route from "Münsterstraße 15a", it must first be turned
> >   into a coordinate.  On the OSM website, the Nominatim service is
> >   used to do this.  Once the web interface has a coordinate for an
> >   address, it gives that to OSRM for routing.  OSRM snaps that point
> >   to the nearest road, then finds a route.
> > 
> >   You might want to do some digging into how Nominatim determines
> >   address coordinates, and possibly consider adding
> >   `building=entrance` nodes - this (I think) will cause Nominatim to
> >   return a more specific location rather than the centroid of the
> >   building/airport polygon.
> > 
> >   Geocoding is a related, but separate problem.  There are a bunch of
> >   tags in OSM that are used by Nominatim, including `building=entrace`
> >   on nodes, `addr:*` on ways/nodes/relations/areas, etc.  Determining
> >   the best coordinate to return to the user is itself a difficult
> >   problem.
> 
> I have done a lot of geocoding and i have several OSRM instances running
> for different purposes - mostly infrastructure calculation - I am pretty
> shure i know the seperate issues well.
> 
> The point is thats an unsolved problem. And its a day to day problem
> for me as when i do calculate telecoms cable distances i want the
> nearest point on a public road - not the backyard - same problem.
> 
> So yes - Geocoding helps me to find a POI, Address whatever. OSRM is
> responsible to bring me there. 
> 
> Something in the middle is missing. OSRM/Mapzen/Graphhopper solves halve
> of the problem by "snapping to road" which is the brute force
> response to this problem - or - to solve the problem of finding the
> nearest reachable point on the route graph. Reality is more complex.
> 
> Either routing engines need to get more intelligent or more dumb by
> reducing the snap size drastically. Then we would need some "middleware"
> which has its own dataset which might be returned by a geocoder
> as extended attributes.
> 
> An example response would be:
> 
> 	I know where "London Zoo" is - Its at lat,lon. If you want to go there
> 	by car use lat2,lon2 - if you want to go there by foot go to lat3,lon3."
> 
> That could be extended for multiple types of transports, infrastructure
> connect points whatever.
> 
> In my primary mapping area we decided to avoid "area style POIs"
> whenever possible for exactly this reason. Building a centroid on
> an area and routing to the nearest point on the routeable network
> is most of the time not the right answer. You dont want to end up
> in the middle of a multi-acre campsite - you want to be sent to the
> reception.
> 
> Flo
> -- 
> Florian Lohoff                                                 f at zz.de
>              UTF-8 Test: The 🐈 ran after a 🐁, but the 🐁 ran away



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-- 
michal palenik
www.freemap.sk
www.oma.sk




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