[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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