[OSM-talk] Direction, side, part of a way (was: correctly mapping avenues)

[Bernd Raichle]

Hi,


on Monday, 11 February 2008 07:30:03 -0800,
Karl Newman <siliconfiend at gmail.com> writes:
 > On Feb 11, 2008 7:20 AM, Bernd Raichle <bernd at dante.de> wrote:
[...]
 > >
 > > 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).
 >
 > 
 > Big +1 on this proposal. That's exactly what I've been thinking about
 > lately. It's stupid to chop up nice long ways just because the speed limit
 > changes or the way happens to cross a bridge.

Yes!

Nonetheless we have to decide when to cut a long way into two or more
ways.

- In the moment OSM is simple:
  If atleast one tag value of a way changes, begin a new way.

- Using the new relation "Segmented Tag", it gets complex:
  You can have one long way with various tag values for different parts.
  You can have even various "highway=" tag values for the same way!

  * What are the rules ... to start a new way?

  * What are the rules ... if the (ordinary) tag values of the way and
    the tag values in the relation are different?  (IMHO: most
    specific rules, i.e., relation tags precede ordinary tags! :-)

  * What are the rules ... if the tag values of two or more relations
    for the same way part are different?  (IMHO: inconsistency => error)


Best wishes,
  -bernd


PS: Btw, GDF has the capability of "Segmented Attributes", i.e.,
    attribute values which are related to a line feature segment only
    (GDF line feature ~= OSM way).  Nonetheless this capability of GDF
    is _not used_ by the two major map suppliers.  Thus if a line
    feature attribute changes, the line feature is chopped and
    attributes are assigned to whole line features only.