[OSM-talk] Mapping everything as areas

[Morten Kjeldgaard]

On 26/11/2009, at 09.47, Morten Kjeldgaard wrote:

> Conversely, there isn't much you can do with graphs that can't be done
> with areas, and since the "map-drawing" approach has great appeal to
> people enjoying beautiful and detailed maps, the pressure for
> deprecating the graph-based approach in favour of the map-drawing
> approach will be ever increasing.


There is a construction that might "bridge the gap" between areas and
graphs. In lack of a better word, I will call it a "multiplex" for now
(I am sure there's a better word.)

Imagine an area like seen in the attached file (ASCII art). It
represents an area that could be an intersection. On the edges of this
polygon some "hot-spots" labelled A-H have been defined.  The shape of
the polygon and the position of "hot-spots" on the edges is arbitrary
and can be defined by the user.

The nice thing about the multiplex is that lines (ways) can connect to
the "hot-spots" from the outside, and the multiplex itself contains
information about how the hotspots are connected internally.

So for example, if the multiplex in the example represents an
intersection, you would connect B->D (left turn from B), B->F (going
straigh ahead from B), B -> D (right turn from B).  And so on, to make
all other possible connections inside the intersection.  This would
give you an object which would render nicely as an intersection, and
there's of course the option of tagging a bunch of auxilliary
information such number of traffic_lights, directional signs etc.

(This example is for right-lane traffic. In countries with left traffic,
you'd do it differently)

Cheers,
Morten



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