[Talk-transit] [Talk-gb-westmidlands] Naptan alignment

Roger Slevin roger at slevin.plus.com
Tue Mar 31 22:15:37 BST 2009


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: talk-transit-bounces at openstreetmap.org
[mailto:talk-transit-bounces at openstreetmap.org] On Behalf Of Peter Miller
Sent: 31 March 2009 20:51
To: Andy Robinson (blackadder-lists)
Cc: talk-transit at openstreetmap.org; Talk-gb-westmidlands at openstreetmap.org;
'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:petermiller63 at googlemail.com] 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: talk-gb-westmidlands-bounces at openstreetmap.org [mailto:talk-gb-
>>>> westmidlands-bounces at openstreetmap.org] On Behalf Of Brian Prangle
>>>> Sent: 31 March 2009 9:46 AM
>>>> To: Talk-gb-westmidlands at openstreetmap.org; talk-
>> transit at openstreetmap.org
>>>> ;
>>>> 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
>>> Talk-transit at openstreetmap.org
>>> http://lists.openstreetmap.org/listinfo/talk-transit
>
>


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