[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 In countries with left traffic, you'd do it differently)

Cheers,
Morten


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