[mkgmap-dev] Questions regarding routing

Sat Jun 8 07:32:49 BST 2013

Hi Felix,

> 
> The idea behind it was that one could priotize or depriotize roads close 
> to Point X.

okay, understood.
> 
> However it is seriously flawed in so far, that mkgmap:road-min-speed / 
> max-speed doesn't work.
I see no code that handles strings like mkgmap:road-min-speed or
mkgmap:road-max-speed. I guess you mean mkgmap:road-speed-min ?

> If you tag road-min-speed=1, the road previously was road-speed=0 and 
> the command is road-speed=-1, it will actually increase the speed to the 
> min-speed.
> However the intention is only that road-speed>0 are not decreased to 0 
> if that command is given. It should never increase...

I don't fully agree. The default value for mkgmap:road-speed-min is 0, and
my understanding of the current code in r2643 is that 
the final road speed value will never by negative as long as you don't set 
mkgmap:road-speed-max or mkgmap:road-speed-max to a negative value 
(which is not quite logical,but probably ok)
So if one  sets a mkgmap:road-speed-min value of 1, what else could that mean ? 

> 
> 
> Else the problem is, that the distance it works, is very short anyhow, 
> now that roads are split up into very short distances everywhere.

what is very short? I plan to change the code so that it doesn't 
produce short arcs (using the --remove-short-arcs value ).
Do you think the value should be higher?

> 
> 
> To improve routing, a much better approach would be to check the 
> finished routing graph for heavy road-class changes on intersections. 
> Garmin doesn't like to route from a road-class=4 onto a 0-1. Only 2 or 3 
> are liked. The max difference should be 2. However that will be 
> difficult to achieve.
> Also high angles on intersections could have an automatic road-speed 
> decrease by 1 or 2 (depending on the current state) - or even more 
> smoothing out - that is still something going crazy. A turn of 160° is 
> like minimum 1 minute time penalty...

Well, it should be easy to implement warnings, but I don't see how mkgmap
could change the values.

Gerd

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