[mkgmap-dev] Commit: r868: Implement routing for .osm input files.

Wed Feb 11 15:15:41 GMT 2009

Mark Burton wrote:
> Hi Paul,
> 
> Thanks a lot for the feedback. From what you report, it sounds like 
> the new map worked quite well with no really bad problems.
> 
>> Given that I'm comparing gmapsupp.img files for combined England,
>> Scotland and Wales previously created by using osm2mp and mkgmap with
>> .mp files and now directly with mkgmap from .osm files then the initial
>> observations are:-
>>
>> Using the osm2mp method gives a final file of 119.8MB where the direct
>> conversion gives a final file of 103.7MB
> 
> Hmm, did it only include 90% of the roads?

I don't know how you'd tell!!

> 
>> Support for roundabouts seems less well implemented. On approaching a
>> roundabout I would previously receive an instruction to "Take 3rd exit
>> at roundabout". Approaching the same roundabout I was simply told to
>> "Keep left to Bloggs Road" even though I needed the 3rd exit.
> 
> OK - the attached new lines file should fix that (this goes in
> resources/styles/default).

Helped but is still not as it was but I note that r877 has roundabout
updates. A quick glance at the text description for a route using r877
has the "Take 3rd exit at roundabout" direction so this may already have
been fixed. I'll see what the graphical map does when I go home

>  
>> Slightly different routes are now chosen. These are not wrong - Just
>> different to before. e.g. Leaving work I always ignore the Garmin route
>> as it's not the best. When it recalculated it previously chose the route
>> I actually take. Using the new file it picked a different route which I
>> had to ignore a second time before it chose the route I actually take.
> 
> Was the new route completely silly or merely sub-optimal? If the later,
> how could it have improved the route?
> 

Sub-optimal. The best route home for me is to use 2 motorways (think the
2 shortest sides of a triangle) whereas the Garmin has always tried to
send me along the hypoteneuse. Unfortunately whilst this is shorter this
is an A road which goes through three middle sized towns and therefore
has traffic lights B roads etc all the way along so takes considerably
longer. Previously after the first recalculation the Garmin would send
me along the motorway. Now it tries to get me back onto the A road until
the second recalculation.

> Tweaking of the road classes and speeds in the lines file should alter the
> behaviour so you could try adjusting those values. I thought I had set
> them to the same values used by osm2mp.
>  
>> I also noticed today that with both versions of the .img file any
>> routing from the Rochdale area along the M62 fails at around the point
>> that the M621 splits from the M62 (approximately J27). I realise there
>> could be many reasons for this but I thought I'd mention it.
> 
> Does a split between map tiles occur there?
> 
Yes the split in the tiles would appear to be here. Further testing
*"suggests"* that I can't route anywhere off the starting tile. I could
try increasing the overlap in splitter to see if this helps but I also
don't seem to be able to route into Scotland or Wales. I've also noticed
these places show in the "Find Cities" list without distance or direction.

Cheers

Paul