On Sat, Apr 10, 2021 at 01:53:11AM -0700, damian....@gmail.com wrote:
Hello,
Recently I noticed that OsmAnd gives wrong micro commands for this trip:
https://www.openstreetmap.org/directions?engine=graphhopper_car&route=50.24294%2C19.02449%3B50.24375%2C19.02432#map=19/50.24347/19.02482
This is the problematic lane:
https://www.openstreetmap.org/way/369873813#map=19/50.24362/19.02465
OsmAnd shows that I should turn right, but there is only ability go to
through.
I think that OsmAnd and also OSMR has problem with interpretationof this
tag: turn:lanes:forward
<https://wiki.openstreetmap.org/wiki/Key:turn:lanes:forward?uselang=pl>
[image: Screenshot_20210409-194817034.jpg]
From OsmAnd's viewpoint, I would say that stating "right turn" is
proper, given the data OsmAnd has to use to decide what to signal.
Do keep in mind that the *only* data OsmAnd has are the OpenStreetMap
ways and the tags thereupon. It does not know how the aerial image of
the intersection appears, nor does it know how a human mind would
interpret the same intersection.
Looking at the OpenStreetMap data, what OsmAnd sees is a single line
(Francuska) denoting the "center" [1] of this road. It is tagged as
three lanes and residential, but the geometry that OsmAnd sees is a
perfectly straight three lane road where all three lanes end at an
intersection with Ceglana and the continuation of Francuska as a
tertiary road.
Rough human eyeball guess of the angle of intersection between the
residential way and the tertiary way, I'd guess it to be about 75-85
degrees (i.e., nearly a perfect 90 degree T style intersection).
So OsmAnd sees three lanes, intersecting with another road at about an
80 degree angle, and all three lanes intersecting at the exact point
where the residential way connects to the tertiary way. I.e., nothing
in the OpenStreetMap data would allow OsmAnd to deduce that there is
really only one lane intersecting at 80 degrees (the left lane,
presumably marked "left only", but the Bing images were taken with cars
covering the roadbed) and a second, slip lane, that forks off from the
residential road and smoothly rejoins the tertiary portion of Francuska.
Humans see that, because we interpret the visual aspect of the world in
that spot. OsmAnd has only the OpenStreetMap data, which says three
lanes go arrow straight until they join the tertiary road at a single
point, and at about an 80 degree angle.
So given the near 80 degree angle of intersection, if the only data you
have available is "three lanes, intersecting at a point, at an 80
degree angle" and nothing else, this looks like a typical "right turn"
intersection. Therefore I am not at all surprised that OsmAnd picked
to say "turn right".
Note, I also question (slightly) the tagging of "left|through".
"Through" is defined as "straight only"
(https://wiki.openstreetmap.org/wiki/Key:turn:lanes:forward?uselang=pl)
but if one were to continue "straight" at this intersection, one would
quickly depart the road, cross a footpath, and somewhat quickly impact
with a building (by the looks of the Bing images).
If I were to have been tagging this intersection, and only used a
single way to represent the resident ail street, I think I would have
picked "left|right" for the turn lanes tagging (due to the 80 degree
intersection with the tertiary road).
If you wanted to make fixes, I'd say the better fix would be to give
OpenStreetMap much more detail on the actual real world geometry of the
intersection. I.e., split Francuska into two ways at the point prior
to the intersection where the slip lane becomes a full lane. Reduce
the lanes count on the original straight section to two and adjust the
turn lanes tag appropriately. Then add the right side slip lane as an
additional, single lane, one-way way that smoothly breaks from the
residential road and later smoothly merges back into the tertiary road
at a point representative of where the slip lane would disappear in the
real world.
Then OsmAnd would see two "intersections" occurring at a shallow angle
(15-20 degrees?) rather than a single sharp (80 degrees) angle, and it
would have more data available to choose to say "slight right" or "keep
right" instead of "turn right".
Note -- I have only observed the existing data. I am located half a
world away from this intersection and so any edits would be better made
by someone who has, or can obtain, local knowledge from visiting this
intersection.
[1] "Center" in quotes because the way seems slightly offset in the
Bing imagery, but I have not aligned the Bing imagery for this part of
the world, so I can't say the way is not properly aligned. And the
OpenStreetMap definition is that the "way" denotes the center of a
road.
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