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<p><font face="Verdana">Thanks for this example, it gives us the
opportunity to look at it from the perspective of what we have,
and how this can be used, even if it is for the renderer.<br>
If you allow me I like to clarify in relation to a very similar
situation, a large junction with the same number of six streets,
no lane markings, as we have thousands across the world, where
vehicles cross this big asphalt surface as they please or guided
by a traffic officer, mostly taking the shortest route.</font><br>
</p>
<div class="moz-cite-prefix">On 23/03/2021 14:14, Sinus Pi wrote:<br>
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<div dir="ltr">Take a large plaza with, say, six different streets
entering. In practice, the whole area is open for pedestrians,
so they'll cross it however they please, probably taking the
shortest routes between streets. What choices are there to make
a router's job easier?
<div>- Draw a "spider" of streets, connecting at the center of
the plaza: easiest for routers, horrible for renders.<br>
</div>
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Yes, easy for router. Horrible for a renderer ? I am not so sure.
What is the intend or purposes of the renderer: render routes or
mimic a satellite imagery ? Or both ? If the surface of the square
is mapped, it looks awful if you want to mimic imagery. However if
the square is not mapped as an area, it will look even more awful
because the renderer will show a big void in between our six
streets. Is a "virtual" tag going to solve this, no. Because in
either situation the routes are equally virtual, as in our standard
tagging. The renderer should check if the area containing the
routes is available in OSM to make that decision.<br>
On my junction example it's exactly the same. It also looks horrible
if you try to mimic imagery. However, although not commonly
practised, we have landuse and landcover tags to map the areas
occupied by highways and junctions. So for a router, no need for
additional info, for a renderer, look for the area to decide if you
want to render the route or not.<br>
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<div>- Rely on the plaza shape to be routable: line-of-sight
optimization is supported by some routers, so the dreaded
around-the-perimeter routing isn't the only way, but it could
take ages for routers to adopt a proper algorithm.</div>
<div>- Draw virtual highways: easiest for routers, but now the
renders would have to know not to draw them.</div>
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</blockquote>
I think this is addressed in my answer above. Adding a tag "virtual"
will not address this rendering problem, in the contrary, will
create a lot of voids in the rendering. A renderer that wants to
mimic imagery only must look at areas, a rendering serving both
routing and physical appearance should render both. In that case it
would be easiest for the renderer to just adopt the "organised"
highways provided by OSM, being it spider or a seperate highway
tagged way along the perimeter.<br>
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<div><br>
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<div>As for Bert's approach, that ALL highways are essentially
virtual the way we use them - it's one thing to draw a line
along a street, resembling it in real world pretty accurately,
and another to draw a virtual river across a lake or a canal
across a sea, resembling a route that doesn't physically exist
at all.</div>
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<p>I completely disagree.Most rivers and canals are very
distinguishable physical ways. Visible on the water with buoys,
under water by dredging, deeper "canals" by use, river flows into
the lake with deeper areas , avoiding fishery zones etc.. It's not
that their is some water on the surface instead of air that you
can't recognise it. On clear water lakes these routes are even
very distinguishable on satellite imagery. Can be perfectly mapped
without a virtual tag, because waterway is for mapping virtual
routes. Rivers wide or small, map the waterway along the deepest
part of the river.</p>
<p>So, still my conclusion: what we have works fine, both for the
renderer and the router, what you propose has no added value, in
the contrary will cause even more complexity for a renderer.</p>
<p>Greetings,</p>
<p>Bert Araali<br>
</p>
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<div dir="ltr" class="gmail_attr">On Tue, 23 Mar 2021 at 11:37,
Bert -Araali- Van Opstal <<a
href="mailto:bert.araali.afritastic@gmail.com"
moz-do-not-send="true">bert.araali.afritastic@gmail.com</a>>
wrote:<br>
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0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p><font face="Verdana">I am sorry but I am still not seeing
the advantage or added value to introduce keys or values
to indicate that something is "less visible" or "less
verifiable" or virtual or whatever you call it. I can't
fit it in the model that exists in my mind how we map
things, especially ways in OSM.</font></p>
<p><font face="Verdana">All highways, all their connections,
all rivers are virtual in OSM, all routes are virtual.
We map them by drawing and connecting ways across
surfaces. A pavement that stops "early" doesn't mean
the path, the route people walk stops there. That is
insufficient completeness in the mapping. Every highway
or lane is mapped with a "virtual" line in the middle,
the "virtual" route people or vehicles follow across a
surface, be it asphalt grass or whatever.<br>
Ferries and boats move across a lake on "virtual"
routes, they just follow a path on the water surface, in
many cases not aligned by buoys or other means.<br>
The same for coastlines, the "virtual" coastline is
where the median is between the salt and fresh water.
In cartography many times just a straight line. You
want to indicate the river connects to the water body
and which route boats or ships follow, you map it, with
our present complete "virtual" waterway schemes.<br>
I still have to see the first example where that doesn't
apply or is not described nicely in our wiki.</font></p>
<p><font face="Verdana">What does adding an additional tag
add to this concept ? Makes it more complex to the
mapper, because he has to add a tag for something
considered more virtual in an already virtual scheme ?
What is the added value for the mapper, I see none.<br>
What is the added value for the router ? I can't
imagine even one? Do you think routers will evaluate
the virtual tag, no they just look at the ways, the
routes in general that are already there. Knowing that
it is perceived as more virtual by some has no added
value for the router.<br>
For the renderer, other data users ? Any added value for
a virtual or invisible tag in comparison with what we
already have ? I can't find any. <br>
Please show me an example where the current tagging
would be considered less favourable to be used as is ? <br>
<br>
So, thank you for making this proposal, you made some
nice examples which we could maybe add to the highway
page. But it's just examples how OSM provides a bright
and consistent way to map complex realities and
behaviour, AS IS. It works, use it as intended, don't
make it more complex by adding tags without added value.<br>
</font></p>
<p><font face="Verdana">Greetings,</font></p>
<p><font face="Verdana">Bert Araali</font><br>
</p>
<div>On 23/03/2021 12:38, Martin Koppenhoefer wrote:<br>
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<pre>sent from a phone
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<pre>On 23 Mar 2021, at 10:23, Niels Elgaard Larsen <a href="mailto:elgaard@agol.dk" target="_blank" moz-do-not-send="true"><elgaard@agol.dk></a> wrote:
Can anyone give an example of such a sophisticated router available to OSM users?
</pre>
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<pre>the routers don’t have to be sophisticated if you connect highways to polygon highways, it’s sufficient for most cases to route around the borders (will be a little bit longer, but mostly not have practical consequences for the suggested route)
Cheers Martin
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