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[mkgmap-dev] Distorted lines

From Gerd Petermann gpetermann_muenchen at hotmail.com on Fri Sep 20 08:47:57 BST 2013

Hi Andrzej,

I think there is no way to avoid the rounding errors caused by the 24b bit limit, but
some problems are definetely caused by the short-arc-removal routine which
merges nodes which are too close.
The weakness of the algo is that it doesn't care about the "importance" of a road
nor about the effect on straight lines. 
I will need a few days to dig into this again.


Date: Sun, 1 Sep 2013 03:48:17 +0200
From: popej at poczta.onet.pl
To: mkgmap-dev at lists.mkgmap.org.uk
Subject: [mkgmap-dev] Distorted lines

I observe badly looking lines. I have attached some pictures and xml 
objects that doesn't look good on Garmin map.
My guess is that there is no proper simplifications for resolution 
24bit. Points too dense are removed in a non optimal way which can lead 
to jagged curves. This could be the reason for bad looking tram railways 
(file tram1.osm in test.zip).
Other reason could be removing of short lines. I think in this case some 
nodes are moved. It looks like instead of creating a new node in a 
middle of removed line, first point is used. This can lead to bigger 
distortion. This is probably the case of road example (file road1.osm).
Best regards,

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