[mkgmap-dev] Still problems with remove-short-arcs

Mon Oct 28 09:02:23 GMT 2013

Hi Carlos,

just to clarify: You say that   remove-short-arcs=0 introduces the sharp angle.
This is not true, as remove-short-arcs=0 will not move anything.  In fact,
the sharp angle is caused by the rounding to Garmin map units.
The green line in the screen shot shows the line that is used after
rounding. You see that the rounding introduces an angle of ca. 75°.
So why does rsa=3 help? Because it flatens the angle as it removes 
one point. You can get the same effect if you move one of the node
975733410 a little bit.
The problem disappears when I add a few lines in the code to make to sure
that the calculated bearings are closer to reality (means I overwrite the values).
I thought that the check-roundabout or adjust-turn-headings options were 
meant to do that, but they don't seem to help.
I think the reason is that adjust-turn-headings doesn't treat roundabouts
special. 
I see two possible solutions when 
we detect the situation that the rounding has created an angle which is too sharp
to be reasonable in a roundabout:
1) Overwrite the calculated heading values 
2) Try to find the point that was probably rounded wrong, and change its
coordinates. This would have to be done much earlier in the chain.

Both will fix routing , but only 2) will help regarding the ugliness
of the displayed roundabout. I try to code option 2), maybe both are
needed because some roundabouts in OSM are divided into small
fragments.

Gerd

Date: Sun, 27 Oct 2013 19:09:43 +0100
From: cdavilam at orangecorreo.es
To: mkgmap-dev at lists.mkgmap.org.uk
Subject: [mkgmap-dev] Still problems with remove-short-arcs

I still get some wrong routing at some roundabouts using 
remove-short-arcs=0. See attached screenshots.
At http://osm.org/go/b_YMZ7sDP-- MapSource makes a detour to avoid the 
roundabout, due to a sharp angle that is introduced by 
remove-short-arcs=0. If I use rsa=3, the route goes through the 
roundabout, but the exit number is wrong, because the incoming road and 
the first street are joined at the same node of the roundabout.

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