Peter I think it is important to separate out the infrastructure of shelters from the function of the bus stop - the shelter is often located where it can be fitted in ... and it can be mapped as a physical object. A bus stop represents a function - the boarding or alighting of passengers. It may be indicated in the physical world by a "pole in the ground" - which might be close to the roadside, or might be at the back of the footway. In my view the "stop" that NaPTAN records represent is the point at which passengers board or alight ... either the point marked by the pole in the ground if it is close to the roadside, or a similar point which might be indicated by a post displaced from the roadside (or it might simply be a point which is not marked - but is clearly recognised by custom and practice. If there is a lay-by, then this is a widening of the road carriageway - the bus stop location should still be close to the edge of the footway at the back of the lay-by. Taking your three (?) possibilities, I think all this means that it is what you labelled "4".
By the way - for those importing data for Birmingham, there was mention earlier this evening of "the marker for stops in Birmingham" in the context of stops that might be missing. I am unclear what this marker is - as NaPTAN does not contain a marker for Birmingham, per se. I can think of ways this might have been determined using the NPTG locality association - is that what has been done? If so the missing stops may simply be in a child locality which hasn't been correctly associated with Birmingham as the parent locality. Best wishes Roger -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Peter Miller Sent: 31 March 2009 20:51 To: Andy Robinson (blackadder-lists) Cc: [email protected]; [email protected]; 'Brian Prangle' Subject: Re: [Talk-transit] [Talk-gb-westmidlands] Naptan alignment On 31 Mar 2009, at 20:22, Andy Robinson (blackadder-lists) wrote: > Peter Miller [mailto:[email protected]] On Behalf Of Peter > Miller wrote: >> >> 4) I notice that sometimes the NaPTAN stop and the OSM one are some >> significant distance apart which begs the question about which one is >> right. > > I've noted this too. I'm going to do a precise check in my area to > see what > accuracy I place on the NaPTAN positions. I've also from today > started to be > more precise about getting the position of bus stops when I survey. > I should > be within 0.5m +/- the GPS accuracy (generally sub 5m with this > Legend HCx I > use). If you are getting that precise it will be useful to agree where the stop should be. We might have a number of points 1) A pole and/or a shelter 3) Optionally a lay-by where the vehicle stops 4) A spot where one would expect to stand to get onto the bus (opposite the door). Can I suggest that it might be appropriate to use the position of the pole and/or shelter as the reference for the bus stop and applications should then assume that the bus stops at the road edge with its doors at the nearest point to the shelter. If that is not the case then possibly we need a 'stopping point' node next to the road to show where the front doors of the vehicle would be. Should we also create a 'lay_by' or 'bay' attribute to say if there is a place for the vehicle to pull in to pick up passenger. It might be neat to be able to describe what sort of facility is provided. In some places it will be a pull-in pull-out bay, in others it might be a pull up, reverse out bay. If we have that information then future rendering engines will be able to get it right. This is what I mean by pull-in pull-out http://www.palmengineering.com/images/busBay4.jpg And this is a Pull-in reverse-out one http://www.broward.org/bct/images/browardcentralterminal.gif Regards, Peter > > > Cheers > > Andy > >> >> >> Anyway, it looks like the detective work is now starts! Great work. >> >> >> >> Regards, >> >> >> >>> Cheers >>> >>> Andy >>> >>>> -----Original Message----- >>>> From: [email protected] [mailto:talk-gb- >>>> [email protected]] On Behalf Of Brian Prangle >>>> Sent: 31 March 2009 9:46 AM >>>> To: [email protected]; talk- >> [email protected] >>>> ; >>>> Thomas Wood >>>> Subject: [Talk-gb-westmidlands] Naptan alignment >>>> >>>> Thomas >>>> >>>> I've also looked at Google maps and their alignment is off too in >>>> exactly >>>> the same way ours is in areas I know well and have surveyed, so I >>>> guess >>>> it's down to the NaPTAN data. There are examples where I know the >>>> bus stops >>>> are in a row along the street (Corporation Street and Acocks Green >>>> Village >>>> for example) but NapTAN has one or two skewed from the line by >>>> several >>>> metres. Currently I favour correcting the NapTAN data to what we >>>> know on >>>> the ground, but until a consensus emerges I'm laying off the urge >>>> to >>>> correct it. >>>> >>>> Regards >>>> >>>> Brian >>> >>> >>> >>> _______________________________________________ >>> Talk-transit mailing list >>> [email protected] >>> http://lists.openstreetmap.org/listinfo/talk-transit > > _______________________________________________ Talk-transit mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-transit _______________________________________________ Talk-transit mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-transit
