[OSM-newbies] highway=traffic_signals

[Dave F.]

Replies in-line...
> One could argue that your traffic signal placement is inaccurate.
>   

I should have said *more* accurate in my previous reply.

> The signals on North Parade Road (687898571) are placed right on the
> way, but in reality they are on the left (north) side of the road.
> Similarly, the signals on southbound Pulteney Road (687898570) are on
> the way, rather than on the left (east) side of the road.
>   

See my reply to Pieren.

> The lights for northbound Pulteney Road (687898568) are in the middle
> of the street, so we can play along with your placement.
> What about the set of light underneath the railway overpass on the
> east side of the roadway? You never placed a node for them! 

There aren't any. The pedestrian crossing affects the other signals.

> (BTW, who
> is supposed to look at those lights?)
>   

I'm not sure I understand what you're saying.

> As Richard indicated previously, the map is an abstract representation
> of the real world. Placing a single node at the intersection of the
> ways with the traffic signal associated with it tells us that this
> intersection is controlled by traffic signals.
>
> If you're going to micro map, then place the signals at the exact
> location of the poles, but then you should also be mapping the edges
> of the road, and not just a single line down the center of the
> roadway. You would have to map the edges of the sidewalk as well, to
> define its location. You couldn't just put a point down for a garbage
> can, but you would have to define a square or circle of the proper
> size so that it renders properly.
>   

I'm not convinced by the use of the word abstraction to describe a map - 
it's just a representation.

I'm trying to map as accurate a representation I can given the tools & 
time I have available to me. Placing the three nodes is *more* (but not 
fully) accurate.
I will continue to map in this way to make the map more useful.

> When creating a map, we really need to decide if we are creating an
> abstract representation of the world, or a photo-realistic
> representation.
>
> This is probably the biggest downfall of the open concept of OSM. Each
> mapper has a different idea of what the OSM map should look like. I
> think there should be a single node at the intersection defining the
> traffic signals, and you think there should be three nodes depicting
> the four traffic signals. We can play editing war till the cows come
> home, and no one wins.
>
> Unless there's a uniform agreement, it ends up that the user is the
> one that loses.
>
> Have look at your example (http://osm.org/go/eukjJQRVR--), and then
> look at this example (http://osm.org/go/eu9dRo8@J--)
>
> Based on looking at the first intersection that you have mapped, I
> would assume that the lights on Rotherham Road in the second example
> would be controlling the intersection with Cliff Hill, where in fact
> the light on Rotherham is a pedestrian controlled light for a
> crosswalk, and there are no lights at Cliff Hill.
>   

That's a failing on three counts:

1. The tagging is not accurate (no crossing tag)
2.The rendering doesn't distinguish between a traffic-light & a separate 
pedestrian crossing.
3. (to a lesser extent) You not understanding the representation. Don't 
you think that as there should be three nodes, that one might represent 
something different?


Cheers
Dave F.