James Ewen wrote: > On Sat, Apr 10, 2010 at 5:01 AM, Dave F. <[email protected]> wrote: > > > >>> 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. >> > > http://tinyurl.com/y965w7r > > You should be able to see the lights in that Google Street View. They > would be pretty hard to miss. If you're going to micro map the other > three light poles, then this one should be included as well. >
Right, OK, let me clarify my understanding of traffic lights. The nodes I place represent not only the actual lights but also where the vehicles are meant to halt. I see it as a type of barrier. That pole is a combination of two lights for traffic travelling different directions who's halts are positioned at the nodes. Similar to the one in the middle of the pedestrian crossing. > >> I'm not convinced by the use of the word abstraction to describe a map - >> it's just a representation. >> > > Webster's Dictionary says: > > Abstraction: > The act process of leaving out of consideration one or more properties > of a complex object so as to attend to others; > > Representation: > That which represents. Specifically: (a) A likeness, a picture, or a model; > > Kind of the same thing, huh? > > >> 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. >> > > Useful to whom? As Pieren stated, statistically, more people represent > traffic signals with a node at the intersection of the ways, not some > distance away from the controlled intersection. > That doesn't necessarily make it right. > As for your suggestion that one can determine which direction the > lights apply to by calculation based on locality rules, one does not > have to do this when the node is placed at the intersection of the > ways. > > The example below on Rotherham would suggest that the eastbound > traffic only has to stop, when in fact both directions have to stop > for that light. > Because of it failings which I pointed out below > >>> 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) >> > > I guess then that your representation is a failing as well, as you > have no crossing tag. > Not sure what you mean. The one nearest the railway does. > >> 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? >> > > Exactly my point. A traffic signal node in the middle of a single way > would be interpreted as controlling that point (node). A traffic > signal node at an intersection would be interpreted as a traffic > signal controlling that intersection (node). Both the same > interpretation. > For my example, where would you put the pedestrian crossing? If you add it as a separate node that would a misrepresentation as there's not a separate set of lights. > In the Rotherham Road instance, I'm going to assume that I will find a > traffic signal mid-block, and not at the intersection of Rotherham > Road and Cliff Hill. Further down the road at Rotherham Road and > Addison Road, I'm going to assume that I will find a set of traffic > lights controlling the intersection. > > With your method, if I find a traffic signal in the middle of a way, I > have to scan the adjacent area to try and determine if I am looking at > a traffic signal controlling traffic on that way, or if it is a > traffic signal that is part of a larger set controlling an > intersection at some distance away from the node. > OK, let's assume the renderings been improved & they are different for traffic lights & pedestrian crossings. Other than a crossing I can't think of a reason why there would be lights on a road with no junctions so a traffic light would by default be used at an intersection. > BTW, isn't a discussion about how to tag various items a good thing > for a newbies list? The concepts here about micromapping of traffic > signals can be extrapolated into other areas as well. I agree. Some think long discussions on here bores & confuses the newbies, & they should be moved to other groups, but as long as they're (hopefully) clear & don't descend into a slanging match, I see no problem. > I am still > reluctant to map a whole lot of details because I do not have a well > developed set of "rules" that I would use. I am still gathering > information about how to map things, and I've been a part of the OSM > community for a few years now. I don't want to spend a whole lot of > time and effort doing things wrong only to have to go back and redo > all of the work to make it correct. I see it as learning on the job. I mapped things then months later gone back & added/corrected them as I learnt. I think the map is better with something that may not be fully complete or correct rather than empty. Cheers Dave F. _______________________________________________ newbies mailing list [email protected] http://lists.openstreetmap.org/listinfo/newbies
