[mkgmap-dev] Turn Restrictions using three ways - design guide for OSM mappers?

Sat Oct 5 06:43:56 BST 2019

Hi blc,

the code that produces these warnings is this:
                if (valid && !viaWays.isEmpty() && restriction.startsWith("only")){
                        log.warn(messagePrefix, "check: 'via' way(s) are used in",restriction,"restriction");
                }

So, mkgmap considers them valid, but dubious. I think that's what they are. The restriction says something like
"when you want to travel from way A via way B to way C you MUST travel from A via B to C"
What kind of restriction is that? In my eyes, the given example is completely obsolete.
On the other hand, a "no-" restriction with via way(s) means
It is not allowed to go from A to C via B. This cannot be expressed with a single via node.

Hope that helps?

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von blc <blc+mkgmap at mail.vanade.com>
Gesendet: Samstag, 5. Oktober 2019 06:31
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: [mkgmap-dev] Turn Restrictions using three ways - design guide for     OSM mappers?

Hello, I thank all who have been working on this neat program to allow our
otherwise old Garmins sit in the dust heap when we can't afford to
subscribe to new maps.

I've been trying to improve the quality of OSM by fixing the errors
that mkgmap emits, which a lot of times mirrors what's seen in
KeepRight.  However there's one variant of turn restriction I've noticed
that warns in mkgmap but do not show up in KeepRight (and iD seems to
understand this type of turn restriction) - the way-way-way type
restriction where three connected ways are in series for non no-u-turn
restrictions.

example:

Turn restriction (only_left_turn) 2256354 (at
https://www.openstreetmap.org/?mlat=47.777585&mlon=-122.319488&zoom=17)
check: 'via' way(s) are used in only_left_turn restriction

The way-way-way type is the proper method for restricting u-turns
on dual carriageway roads which is understood by mkgmap.  On the
other hand, iD and KeepRight it seems to be valid to do way-way-way
instead of way-POINT-way for no/only left/right turn restrictions, no/only
straight on restrictions, etc.  I've seen a lot of the non no-u-turn
way-way-way restrictions in the USA.

These type of non no-u-turn restrictions seems to cause a warning in
mkgmap and probably not translating them.  My question is that should
these be supported in mkgmap, or should these be fixed in OSM so that they
are simple way-via-way despite iD and KeepRight seem to claim them
valid?  Or perhaps way-way-way is deprecated but still supported by OSM
but should be changed to way-point-way?

way-point-way = relation
from: some-street-way
via: some-intersection-point
to: some-street-way
(this is the most common type of turn restriction)

way-way-way = relation
from: some-street-way
via: some-street-way
to: some-street-way
(this is necessary specifically for dual carriageway u-turn restriction,
but it's used for other types as well which mkgmap complains about.)

Thanks for shedding some light on the discrepancy here!  Note: I'm
currently depending on OpenMapChest data for mkgmap runs as my computer
and internet connection are not large or fast enough for the quantity of
data I'd like to work with.
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