Navigation lane assist

[ToFuCH]

Hello,
For a while now, I'm using OSMScout as my daily car navigation and generally it works well, specifically on standard 2-lane roads. However, on multi-lane highways the verbal directions and the lane assist are generally useless, often misleading, sometimes outright wrong, rarely correct. Therefore, I usually pan an zoom to see where the blue line is going. Here two examples from a highway in Switzerland, which I often use. But the same difficulties exist e.g. in Germany, France or UK.
When travelling north on highway A3/A4 at Limmattaler Kreuz west of Zürich heading towards Bern, Basel you have to take the leftmost lane, which will lead westwards as the blue routing on the screenshots shows. However the lane assist suggests the two right lanes, which will go east. Also the arrow at the top-left corner shows right for each and every motorway intersection, even if you have to turn left. I have checked the road designations on OSM and to my view they are all correct and complete.
A3_Limmattal_Basel: https://www.openstreetmap.org/edit#map=18/47.40883/8.42590
Another question to the lane assist: Sometimes it shows arrows, sometimes dots, what is the difference? I could not yet figure this out.
Generally the lane assist should also appear earlier already to allow for a safe lane change, sometimes across several lanes. Currently it shows up, when you should actually already be in the correct lane.

Similarly on the same highway southbound at Zürich-West the lane assist shows the two leftmost lanes, while my route turns right. A few meters later already on the exit the next turn is shown correctly. Again OSM appear to be ok.
A3_Zürich-West_Wettswil: https://www.openstreetmap.org/edit#map=19/47.34178/8.45341

In this case there is no guidance at all at the motorway intersection:
A1_Rütihof: https://www.openstreetmap.org/edit#map=16/47.4465/8.2526

Further some examples of errors in the route calculation:
Here the route was asking me to use an emergency only exit from the motorway
A3_Emergency_Exit: https://www.openstreetmap.org/edit#map=18/47.48385/8.09511
The screenshot was taken after the recalculation because I did not take the proposed exit :)

Here the route started along a road, which is restricted to local traffic although my destination was miles away.
Villnachern: https://www.openstreetmap.org/edit#map=18/47.47042/8.16492

The reason for this routing I cannot understand. I took the red line without any issues and much faster. The destination was far north of the screenshot.
Derendingen: https://www.openstreetmap.org/edit#map=16/47.2044/7.5844

I can't see any reason on OSM, why to turn slightly right here:
Mönchweiler: https://www.openstreetmap.org/edit#map=19/48.09542/8.43044

It would be great if you could look into these topics, whether it can be optimised in the coding of OSMScout.
Kind regards, Torsten.






![Mönchweiler](https://github.com/Karry/osmscout-sailfish/

assets/95654866/a0214692-e7f6-4abc-a315-fe70544306af)

[Karry]

Hi. Thank you for report! I really appreciate it. I will write detailed reply later, now, just in short - I know that navigation instructions are really bad. I plan to focus on improving routing / navigation instructions this year...

And sorry for all the pain, caused by using my app :-)

[Karry]

Hi. Sorry for late reply, this year is pretty hectic for me. I will pickup questions and bugs from the simplest one:

Another question to the lane assist: Sometimes it shows arrows, sometimes dots, what is the difference? I could not yet figure this out.

When mapping highway lanes in OpenStreetMap (turn:lanes), you may specify that lane has no sign - application is showing dot - or you may specify that lane has straight arrow.

Generally the lane assist should also appear earlier already to allow for a safe lane change, sometimes across several lanes. Currently it shows up, when you should actually already be in the correct lane.

I have it on my TODO list :-) Parsing turn:lane tag and provide it to UI was kind of experiment at the beginning, to test how good OpenStreetMap data are in this regards. It is not fully integrated to the code for navigation instructions..

[Karry]

The reason for this routing I cannot understand. I took the red line without any issues and much faster. The destination was far north of the screenshot.

I tried to route from "47.20032 7.59236" to "47.22031 7.60602" and it is reproducible. When using OSRM (Open Source Route Machile) it selects northern route: https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=47.2001%2C7.5925%3B47.2197%2C7.6057#map=15/47.2099/7.5861

When experimenting with libosmscout demos I just found out that router do not want to cross "Luzernstrasse" bridge. It took me some time actually to find out that problem is in libosmscout import code, that is causing that these two ways are not connected in routing graph... Fix is pretty simple at the end: Framstag/libosmscout#1570 for fixing routing, you will need to wait for new map database update.