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[mkgmap-dev] Garmin directing to connected crossing roads

From Gerd Petermann gpetermann_muenchen at hotmail.com on Mon Mar 26 08:08:21 BST 2018

Hi Harri,

I think the problem is that you use type 0x08 for unclassified. This type is special, it should be used for _link  roads.
When you use e.g. 0x06 instead the problems are gone.


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Harri Suomalainen <hsuomal at welho.com>
Gesendet: Samstag, 24. März 2018 13:35:16
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: [mkgmap-dev] Garmin directing to connected crossing roads

I've noticed locations where my Garmin gives directions to use crossing
street (like small service roads) when routing through a single route.

A good example is unclassified "Juurakkotie" at
(I'm using current data from Geofabric extracts and the road has not
changed recenty and it is verified to be as straight as josm makes it)

When Garmin routes through it from west to east, it tells multiple times
to go the the service, to the service, ...about 4 times or so (and I
think only twice when routing from east to west). Map line is straight
through Juurakkotie (ie no routing through yards).

(Not sure what word garmin uses exactly in different languages to the
road type it suggests taking to, but it varies from device to another

My style has following lines:

# To avoid routing through service roads
highway=service { set access=destination }
# Low road class definition for service
highway=service [0x07 road_class=0 road_speed=2 resolution 24]
# Higher road class for unclassified
highway=unclassified [0x08 road_class=2 road_speed=3 resolution 22]
# and in finalize-section
access=destination     { set mkgmap:throughroute=no; set access=yes }

I see no reason why it should consider the connecting routes something
one should go to and instruct so. (My style also should make service
type road avoided anyway for routing if possible).

I've occationally noticed this kind of behaviour with my old Nuvi 755
also (currently using Drivesmart 61). (Getting multiple turn to..turn
to..turn to.. instractions repeated is quite annoying when it happens)

I wonder if this is some kind of "feature" of Garmin or some kind of bug
in stored road geometry or if this is something to deal with my style.

I compile map with following options
--max-jobs=8 --link-pois-to-ways --add-pois-to-areas
--reduce-point-density=3 --merge-lines --reduce-point-density-polygon=1
--drive-on=right --country-name=FINLAND --country-abbr=FIN
--area-name=Finland --latin1 --code-page=1252
--location-autofill=is_in --x-housenumbers --housenumbers
--process-destination --process-exits

This kind of behaviour has existed for years and currently I'm using
latest mkgmap-dev. I run into it only occationally and when I do it is
repeatable in the locations.

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