[GraphHopper] Improve route's geometry

[Peter K]

Hi Nicolas,

this limitation will be removed with solving this issue:
https://github.com/graphhopper/graphhopper/issues/27

BTW: nodes between edges in graphhopper are only stored in wayGeometry
(see GraphStorage), not as real nodes. This was introduced as this
speeds up querying a lot and also space is reduced.

Regards,
Peter.

> Hello,
>
>  
>
> I noticed that routes are computed only between the graph's nodes, and
> the route does not go close enough to the actual GPS points.
>
> I also noticed that there is a small mistake when selecting the
> start/end node when the GPS point falls on an "one way" edge.
>
>  
>
> The current behavior is to find the closest edge to the lon/lat
> coordinates and then find the closest node on this edge to the lon/lat.
>
> When an edge is one way, you don't have to take the closes node on the
> edge but the node that will respect the traffic flow.
>
> Mean if your starting point fall on an one way edge, you'll have to
> start the routing form the end point of this edge, no matter the
> starting point may be closer to your GPS coordinates. Indeed, if you
> go from you gps point to the start node, you'll have to violate the
> one way restriction.
>
>  
>
> (see attachment as example)
>
>  
>
> In this picture we also see the first thing I mentioned : the geometry
> lacks of accuracy between nodes and GPS coordinates ; the blue line
> does not "stop" exactly at the two little flags representing my GPS
> coordinates. (green flag: start, red flag : end)
>
>  
>
> I started digging into the code in order to solve these two issues and
> I came up thinking that the whole API needs a bit of rework.
>
> Right now the node resolution returns a node ID but I think it should
> rather return an EdgeIterator of the matched edge.
>
> With this edge, it's possible to find the appropriate start/end node
> depending on the lon/lat of the point and the fact that edge is one
> way. It's also possible "finish" the road and compute the
> missing/exceeding parts of the road.
>
>  
>
> Am I missing something ?
>
> Do you think that my point of view is correct ?
>
>  
>
> Thank you
>
>  
>
> Nicolas GILLET
>
>  
>
> *Market-IP --*///Creating Mobile Intelligence/
>
>
>
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