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[mkgmap-dev] Simplifying ways

From Felix Hartmann extremecarver at googlemail.com on Sat Nov 28 22:23:30 GMT 2009

Mark Burton wrote:
> Hi Felix,
>> No Johanns (v8) patch actually improves long distance routing (2-3 
>> additional turns), while the remove bogus roads makes long distance 
>> routing worse for me (3-4 turns less). Sorry for the wrong text.
> OK, thanks for clarifying that. My comments in the last message can
> therefore be totally ignored. Mind you, I still don't understand how
> the simplify way patch can work correctly. Perhaps it's time I
> actually tried it out.
>> I have no clue why the remove bogus nodes makes routing worse. v3 actually is 
>> great insofar as it allows several routable roads with different speed, 
>> but so far I have not been able to make such ways opposing oneways - but 
>> they are different speed. Currently playing around to find out how I can 
>> trick it into two opposing oneways (while the oneway is "artificial" in 
>> both directions in so far that I use incomplete rules to set it up).
> The change that v3 introduced could be retro-fitted to trunk as it's
> essentially independent of the bogus node removal.
I don't know what's the difference between patch v3 and patch v2, but v3 
makes no practical improvement. Yes it sets the different speeds and 
road_class for 0x01 and 0x02, but impossible to set different 
restrictions, they are simply dropped.

The following example does output both 0x01 and 0x02 with their 
respective speeds, but does not set emergency=no, does not set 
oneway=no, nor taxi=no:
highway=* & copy=99     [0x01 road_class=2 road_speed=2 resolution 24 
highway=* & copy=98     [0x01 road_class=2 road_speed=2 resolution 24 

highway=path { set oneway=no; set emergency=no; set taxi=no }    [0x02 
road_class=0 road_speed=0 resolution 24]/

The way in question is a path - I just use this quick example because 
when it works, I probably have to put 5-6 hours time into rewriting my 
style-file, so I just use this as a test scenario.

With the restrictions not enacted on the simple highway=path rule, the 
different speeds and road classes are only usable insofar as it could be 
used to have slow ways on top of fast ways so if the GPS/Mapsource 
thinks the quick way means too much penalty time for turning, the slow 
way could be chosen. In reality I think that use will not help a lot 
(though could be interesting to try out for special cases, like motorway 
junctions) - because in 99% of all cases the way with higher road_speed 
will be chosen.
> Cheers,
> Mark
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