[mkgmap-dev] Problem routing over very short roads

Thu Jun 4 12:01:50 BST 2009

Mark Burton wrote:
> Hi Felix,
>
>   
>> Do you see any solution to this problem?
>>     
>
> Sorry, I don't have a plan at this time.
>
>   
>> I think if a way is shorter than 3.4m we get the problem. I don't think 
>> it is because of the duplicate ways.
>>     
>
> It's more subtle than that because I could make a small map (just a few
> 100ms height and width) that included that way and mapsource was quite
> happy with it but when I processed your big file, it didn't like it - so
> either the problem is related to the density of stuff around or the
> size of the area being processed or something...
>
>   
>> Could we maybe have a filter that joins such tiny roads to the ones it 
>> is connected too?
>>     
>
> Well, if it becomes zero length that will happen anyway because that's
> what the new remove-short-arcs option does. What I could do is extend
> that code to allow the min distance to be specified so you could say
> --remove-short-arcs=3.5 and it would zap all arcs under than length but
> without the distance, i.e. just --remove-short-arcs would only zap zero
> length arcs. I will produce a patch to do that, should be quick to do.
>   
Would that connect all notes that are closer than 3.5m together, or only 
nodes that are connected to each other?
My thinking is that if in case a road crosses another on a bridge, and 
now on the top road a node lies within 3.5m of the distance of the road 
below the brige, and then they are joined, this patch would only be good 
for experimenting, but not for really usable maps. If it only deletes 
nodes that are connected anyhow than I think maps will be quite usable.

I suspect the same error to be actually taking place quite often (about 
say every 10. route calculation of aerial distance 30-40km ). Though I 
would have to closely watch autorouting routes more often.

Felix
> Cheers,
>
> Mark
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>
>   
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