[OSM-talk] correctly mapping avenues

Bernd Raichle bernd at dante.de
Mon Feb 11 15:20:02 GMT 2008


Hi,


on Sunday, 10 February 2008 08:34:31 -0800,
Karl Newman <siliconfiend at gmail.com> writes:
 > On Feb 10, 2008 4:21 AM, Frederik Ramm <frederik at remote.org> wrote:
 > > > Since trees lining a way/street are such a common occurence, why
 > > > not have a simple additional tag to the main road.
 > > >
 > > > lined_by_trees=yes/no/left/right
 > >
 > > I'm a bit unhappy about needlessly inflating the importance of the
 > > direction of ways. Long-term, I would actually like to get rid of the
 > > direction and express everything in relations.

This means, that you find it necessary to have something like a
"direction" or a "side", both of this features related to a way?
But you don't want to express a direction or a side by the _implicit
order_ of the way nodes.


 > >                                                 The reasons for this
 > > are
 > >
 > > (a) the direction is too easily changed, sometimes by mistake

... because none of the current OSM editors show direction- or
side-related tags explicitly.


 > > (b) there might be multiple conflicting things that rely on the
 > >    direction, e.g. a road that is oneway from A to B but has a
 > >    slope from B to A
 > >
 > > Anything with "left/right" in it also relies on direction. I'd prefer
 > > "east/west/north/south", or using an explicit relation that says
 > > "trees on the right between nodes A and B along road C".

I am against east/west/north/south because there are a lot of
ways/areas/things which do not go straight ahead.


 > Okay, this thread is at risk of spinning wildly off-topic, but I've been
 > thinking about this situation recently. It seems to clamor for the use of
 > specialized relations that are "direction-aware". That way, if a way is a
 > member of a relation and has directional properties (left/right), then the
 > editors could look for those relations when the way is reversed and either
 > fix them automatically or at the minimum raise a warning dialog.
 > 
 > I also had some other ideas about enforcing referential integrity for
 > another type of specialized relation (if one or more node relation members
 > is required to be part of a way relation member, then enforce that rule).
 > That rule could actually be enforced by the API.
 > 
 > These specialized relations would just give some structure to the wide-open
 > relation type, without implying anything about the nature of the relation.
 > It could possibly be accomplished through special tags on the existing
 > relation structure.

Do you have any propositions how this will look like or how this
should be done?

A few days ago I have started a new proposal for a "Segmented Tag",
which relates a set of tags to a directed or undirected part of a way
(I have called this part "segment" inspired by GDF's "Segmented
Attributes").  I have not found the time yet to finalize the proposal
adding some examples, nonetheless it can already be found in the OSM
Wiki (Relations/Proposed/Segmented Tags).


Best wishes,
  -bernd




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