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[mkgmap-dev] [PATCH v4] - tweeze arc headings to improve routing instructions

From Mark Burton markb at ordern.com on Sun Oct 11 12:02:27 BST 2009

v4 - now writes arc curve data that encodes the final heading of an arc.
This should yield better quality routing instructions when an arc's
final heading differs greatly from its initial heading.

At this time, only single byte curve data is being written and the
format of that is not 100% confirmed but it's looking plausible
(possible doubt over ordering of lower 3 bits).

The --adjust-turn-headings option does not enable/disable the writing
of curve data. If you want to disable the writing of curve data use the
temporary option --no-arc-curves. This option will probably disappear
when the curve data has proven to be reliable.

I have tested this with the GB map and it didn't break the routing.
I was getting good quality routing instructions (with the
--adjust-turn-headings option).

All feedback appreciated.


v3 - now based on r1265. Added --adjust-turn-headings option to enable
this functionality. Reports now downgraded to info (from warn).


v2 - various changes - should now work with junctions that have more
than 1 side road - should be able to treat exits from roundabouts in
the same way as side roads.


The attached patch (which also includes the drive-on-left patch because
it's based on that) attempts to improve the quality of routing
instructions so that when a turn off a road that doesn't involve a big
heading change is required, the GPS should say "turn left/right" rather
than "keep left/right". It can also reduce the number of "keep
left/right" instructions you get when you are not leaving the main road
but passing a junction that has a shallow turn (e.g. sometimes happens
on motorways when it tells you to keep left/right even though you are
not leaving the motorway).

I have tested it a little and it appears to work. I expect there are
situations where it does the wrong thing so it would be great if people
could give it a go and see if it behaves OK.

There isn't any option to enable the feature at the moment. If you use
the patch, it will be enabled.

It's currently issuing a warning for each change it makes but later that
can be downgraded to info.


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