[Interest] Concepts behind Route and navigation

[Marek.Floriańczyk]

Hi

I'm working on car navigation application, I'm using mapboxgl for that.
I have based my app on this example:
https://github.com/tmpsantos/qmapboxglapp/tree/tmpsantos-cheapruler
All is well when I calculate route from start point to end point at the beginning of the 
journey. Problem occurs when user veers off the route and I need to recalculate, car is 
moving ahead so I need to calculate new route in the direction the car is moving, cant really 
do that in a RouteQuery so I'm setting additional Waypoint 10 meters ahead from current 
position - Is there any better way to do that?
Worst of all, when I do that I have additional RouteSegment but Route.path does not include 
all coordinates from RouteSegments.
In other words. First time I calculate the Route 
Route.path.length==RoteSegment[0-n].path.length-n 
(n-number of segments)

When I include additional Waypoint to have Route calculated in direction of driving
Route.path.length!=RoteSegment[0-n].path.length-n

In second case I can't calculate on which RouteSegment I'm currently, because Route.path 
does not have all coordinates from RouteSegment, even If I exclude RouteSegment created 
by Waypoint (btw it should have waypoint and waypoinValid properties but it does not have 
it) it still does not agree with Route.path.

Can someone shed some light why this was designed in this way. I mean is there a better 
way of calculating route along the car driving path and why Route.path does not include all 
points from RouteSegment.path when additional waypoint is included. 
Algorithm for calculating current RouteSegment index does not work in second case. 

Best Regards
Marek
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