[mkgmap-dev] [PATCH v1] - Route centre tweaks

Tue Sep 22 15:02:22 BST 2009


Mark Burton wrote:
> Felix,
>   
>   
>> After playing around a bit on my Vista HCx I did notice slightly 
>> different routing too. The maximum distance that it manages without 
>> "route calculation error" did not change however.
>>     
>
> On the HCx, I just tried an 800Km route from where I live to Thurso and
> it took quite a while (stuck on 100% for a minute or two) but it did
> eventually calculate a sensible route.
>   
Well that's taking big streets. With my maps I'm happy when it routes 
10-40km on the Vista HCx (or max about 50 turns), and 40-150km in 
Mapsource (or max about 150turns).

The only way to really improve this is in my opinion to remove sharp 
turns on intersections - what we talked about last week. Then Mapsource 
will route on for long, long distances and the Vista HCx will go up to 
100 turns (or say 20-40km in really densely mapped areas). Vista HCx 
cannot route over more than 100 turns without Via Points from what is my 
knowledge, so that boundary cannot be removed.
>   
>>> Today's offering includes the table A tweak but it also increases one
>>> of the limits that determine when a route centre needs to be
>>> sub-divided. As far as I can tell, the limit was somewhat smaller than
>>> it should have been. So with this patch, fewer routing centres should
>>> be required (obviously depends on the map data).
>>>       
>> Routing in Mapsource is now different too. So far I have found one route 
>> that does not calculate with the old version, but with the new. The 
>> difference is however 2-3 more turns, so no drastical improvement. Maybe 
>> some routes also degrade?
>>     
>
> I guess that is possible but I would hope that the overall effect is
> beneficial. I'm (optimistically) working on the theory that increasing
> the size of the route centres makes the route calculation
> easier/quicker. That could, of course, be complete rubbish.
>   
I think this is correct, but will not help much for non car centric maps 
(car centric in the way that motorways have few intersections, and have 
no sharp turns on intersections). For car centric maps the patches might 
help more, because here you route over many tiles and therefore the more 
efficient the underlying data, the better.
> With the current patch, my GB map is around 172 MB compared to 180
> without so the space saving is worth having if not dramatic.
>
> Cheers,
>
> Mark
>
>
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>   
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