[mkgmap-dev] Anyone tried the arc tweezing patches?

Wed Oct 14 12:31:08 BST 2009

Mark Burton wrote:
> I have received zero feedback on the recent arc tweezing patch. I
> believe that in its latest form (v4), it provides much improved
> routing instruction quality. In particular, it should give you fewer
> instructions to keep left/right or even turn left/right when you are
> continuing on a long road (like a motorway) that has various roads
> that branch off of it. So please do try it out if you can and report
> success/failure, etc.
>
> Thanks,
>
> Mark
> _______________________________________________
>
>   
Hi Mark,

Okay, I have played around now over 1 hour in Mapsource (allways 
creating two identical route start/endpoints and calculating with two 
maps identical if not for the tweeze arc patch and then comparing the 
choses routes) and just quickly rechecked that my Vista HCx behaves the 
same (and of course it does).

So yes it is a good start, when routing with "faster time" the 
difference of ways chosen is very similar, with "shorter distance" one 
really starts to see the changes:
Usually with the patch distance is about 1-2% shorter and a bit more 
direct. There are of course the odd cases when one route will be instead 
of 50km, 80km km long but this of course is inherent if one route takes 
a "motorway" making a big detour, while the other route is going for 
smaller streets on shorter distance. Calculated arrival time averages 
out pretty well (well a tiny bit faster with the patch on average)

Overall I think the patch helps to iron out the "huge" time penalties 
garmin puts on small angles, and routing instructions get better too. 
Especially it irons decreases a bit the huge difference one might get 
when inverting a route.

I would much prefer however if the original roads stay untouched and 
instead additional junction roads with small angle created instead as 
discussed previously.
This could then even be adjusted so far, that you could set up time 
penalties depending on whether you go from primary to residential road 
(bigger time penalty, as you need to break) vs residential to primary 
road on the same junction in inverse direction (smaller time penalty, as 
on residential road you travelled slower and therefore do not need to 
lower speed so much) or even by deleting the original roads and 
inserting only new "junction roads" create time penalties for say 
traffic lights even when going straight instead of changing the 
road_speed of the whole road section that you can influence with the poi 
+- option.