[mkgmap-dev] Garmin directing to connected crossing roads

Sat Mar 24 12:35:16 GMT 2018

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 
https://www.openstreetmap.org/#map=18/60.29121/24.99298
(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 
anyway)

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
--generate-sea=multipolygon,extend-sea-sectors,close-gaps=2000,floodblocker"
--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.

Chears,
Harri