[mkgmap-dev] special cases with short arcs

Tue Sep 24 18:53:03 BST 2013

Good idea!
It is also possible that the --process-exits and --process-destination 
options might create several ways with short arcs. I should change it so 
that both options do not create ways shorter than the shortest allowed arc.

WanMil

> Hi Andrzej,
>
> thanks for the hints.
> I just wonder if anybody ever tried to use a very simple trick:
> If I remember correctly, we calculate and write the arc length to the img
> file.
> What happens if we just make sure to write the minimum length (e.g. 3.5m),
> no matter how short the arc really is?
>
> Gerd
>
>
> popej wrote
>> Hi,
>>
>> I'm doing similar processing for cgpsmapper. My algorithm is following:
>>
>> First I try to remove very short lines. I don't remove lines which are a
>> part of roundabout, restriction or road sign. I check ending nodes of
>> short lines and don't remove lines if any node is external (on tile
>> boundary).
>>
>> I merge nodes and move them to the middle of removed line. But if a node
>> connects to multiple short lines, I leave it at original position (this
>> is mostly to preserve integrity of network).
>>
>> Then I try to extend remaining short lines. I move both ending nodes
>> unless one of them connects to multiple short lines.
>>
>> I'm working with floating points coordinates but I round coordinates to
>> 24-bit equivalent to calculate length. I remove only the shortest lines,
>> where difference between ending coordinates is no longer than 1-bit in
>> 24-bit range. I simply hope there won't be problems like removing whole
>> bridge.
>>
>> I don't know what is real Garmin condition for short line. Cgpsmapper
>> uses distance 2.4m. I would rather expect that condition is based on
>> 24-bit coordinate grid. Would be good to know precisely, when line is
>> too short, this would minimize the number of changes.
>>
>> --
>> Best regards,
>> Andrzej
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>
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>
>> http://lists.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
>
>
>
>
>
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