[Tagging] Road hierarchy

Julien djakk djakk.geographie at gmail.com
Sat Aug 10 16:25:49 UTC 2019

Hello Paul !

The "old" highway tag can give default values to the 5 new tags, so it
is not necessary to re-map everything :)

Yes you are absolutely right : I need my own renderer to populate the
new tags. I was thinking about putting anything (roads, summits,
footways, towns, trees …) with importance = 1 to the lower zoom, etc.
(Actually tag importance already exists, used for railways, has main
values regional or national).

Julien "djakk"

Le sam. 10 août 2019 à 13:37, Paul Allen <pla16021 at gmail.com> a écrit :
> On Sat, 10 Aug 2019 at 11:42, Julien djakk <djakk.geographie at gmail.com> wrote:
>> Classifying roads should be the same all over the world ! :O
> In an ideal OSM, tagging ANYTHING should be the same all over the world.  Sadly, people
> sometimes insist on fitting square pegs into round holes instead of coming up with a new
> value or even a new key.  I shudder every time I see "In OUR country we use this tag
> completely differently."  Sometimes this list is partly to blame for that - the last time I
> can think of was about tagging polders, with some insisting that existing tagging be
> used for a feature that isn't well-described by them.  But see below...
>> The highway tag shuffles administration grade (in England for example
>> or for motorways), physical characteristics / abutters (example :
>> residential, motorway), access, and importance (commuting and
>> long-distance trip). I think the highway tag should be split into
>> those 5 features : admin_level, abutters, access, commute_importance
>> and long_distance_importance (by experience, there should be 6 levels
>> for importance, from the cul-de-sac road to the main artery).
> Hindsight is 20-20. There's a famous saying in computer programming "Plan to throw
> the first one away, you will anyway."  When you develop something new, you learn
> along the way.  Often you find you've painted yourself into a corner and had you
> known at the beginning what you know now you'd have done some things differently.
> That's how it is with many older (and some newer) OSM tags.  Had we known back then
> what we know now, some of our tags would look a lot different.
> With your proposed scheme there are going to be some people who think it's a
> good idea and others who will see all sorts of problems with it.  Eventually, after
> a lot of discussion, all might agree on something vaguely similar to your idea
> (which would be a lot different to what we have now).  I doubt it, but it's possible.
> Even if we come to an agreement, the problem is implementing it.  It isn't a one-to-one
> mapping, far from it.  And that means EVERY road that has been mapped will have to
> be re-examined in order to figure out how to tag it.  With a one-to-one mapping a
> mass edit would be possible, but with this it's going to be a lot of work.  A hell of
> a lot of work.  There are far too many POIs that are as-yet unmapped to divert all
> our effort into retagging every highway in the world when what we already have is,
> although not ideal, reasonably good.
> If you ever managed to get this flying pig off the ground (you won't) then there's the
> problem of decorating the wings.  Even if you got full agreement from the list, and
> a commitment by every mapper to remap every highway, you also have to convince
> the carto people to render it.  And the editor people to support it.
> There are only two ways you could make this proposal happen.  One is forking OSM
> and convincing enough people to join you that you can remap every highway in the
> world before you all die of old age.  The other is to invent a time machine, go back in
> time and present good arguments to persuade people to invent better tagging.  I'm
> not sure, but I think you might have more chance of success if you go for the time
> machine.
> What you have is another way of illustrating that one of the main purposes of this list
> is to try to use our collective knowledge and experience to avoid introducing tags
> with problems or we'll end up with less-than-ideal tags like our highway tagging.
> OSM evolves and, like biological evolution, that means taking what we already have
> and tinkering with it a little.  Big changes aren't possible, just minor changes that
> result in a design that is far from perfect but is good enough.
> --
> Paul
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