[mkgmap-dev] special cases with short arcs

Tue Sep 24 16:22:37 BST 2013

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
> _______________________________________________
> mkgmap-dev mailing list

> mkgmap-dev at .org

> http://lists.mkgmap.org.uk/mailman/listinfo/mkgmap-dev

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