[OSM-talk] Frustration of an experienced mapper

Martijn van Oosterhout kleptog at gmail.com
Thu Mar 1 12:01:16 GMT 2007


On 2/28/07, Christoph Eckert <ce at christeck.de> wrote:
> Segment IDs
>
> So here we go by a (simplyfied and theoretical) first example. Given the
> fact you have four nodes A, B, C and D. The nodes are connected by
> segments of the same direction, but not in the right order, due to
> editing after their first creation. The segments therefore have the IDs
> 10, 30, 20 instead of 10, 20, 30. Now I make them a way. Guess what
> weird things will happen when the street gets rendered or converted to
> a Garmin map.

JOSM has a command to reorder segments. As far as I can tell it does
the right thing.

> My street consist
> of a polygon formed by its vertices, not by a certain direction or by a
> (potentially non-)consecutive number of segment IDs.

I do agree that on a certain level segments are completely
unnessesary, you could describe ways as an ordered set of nodes. It is
useful though for people to mark roads without making ways straight
away (if they dno't know what they are).

> Polylines would allow for curves defined by three nodes, saving a lot of
> unnecessary nodes, segments and mouseclicks to form a bow. It would
> therefore lead to a much reduced data size and allow for much better
> render results.

There's was some work on bezier curves. It would be nice to be able to
mark a curve "bezier=yes" or "cubicspline=yes" and make nice smooth
roads with very few points.

> As a street usually consists of more than 2
> segments, it often is necessary to delete an existing way and some of
> its segments, to redraw the segments for oneway's sake, to make them
> ways again and to apply all the tags someone else had assigned before.

Again, JOSN has a "reverse segment" command, which will reverse the
segment without you having to touch the way. There is also a "split
way" function which will make a new way and copy the tags to both. One
would hope people are using these tools rather than doing it by hand.

> Currently OSM lives from collecting new data, but editing data will
> become more and more important. Thus I can imagine that we need some
> improvements on the data model, which not only address the issues
> mentioned above but even others. Someone savvy here who can contribute
> some technical/mathematical knowledge about those issues?

Well, the SVG format supports bezier curves and cubic splines, so one
would think that it would be easy to configure it for ways...

Possibly though renderers don't support it yet...

Have a nice day,
-- 
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/




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