[Talk-gb-westmidlands] [Talk-transit] NaPTAN bus stop database import - some moreobservations

[Roger Slevin]

Thomas

Ok - thanks.  I will get a close approximation to this by using current data
with the same filtering criterion - and hopefully, if there are further
questions about any specific aspects of the data, I will be able to respond
to them.

Roger

-----Original Message-----
From: Thomas Wood [mailto:grand.edgemaster at gmail.com] 
Sent: 01 April 2009 18:15
To: roger at slevin.plus.com
Cc: Brian Prangle; Talk-gb-westmidlands at openstreetmap.org;
talk-transit at openstreetmap.org
Subject: Re: [Talk-transit] NaPTAN bus stop database import - some
moreobservations

2009/4/1 Roger Slevin <roger at slevin.plus.com>:
> I would be able to comment more about the missing data and other aspect
> which you and others draw to the list’s attention if I could have a copy
of
> the NaPTAN data that has been put through the import process – can you (or
> someone else on the list) either point me to where I can find that
specific
> data set 
 or can send me a copy of the specific data that has been
> imported?
>

Currently all data as of 25th March 2009 19:47:46 in the West Midlands
region with the a value of Birmingham (case insensitive) in the Town
field.

I am planning to check to see if we missed any stops, and add any
missed based upon a bbox matching.

>
> Best wishes
>
> Roger
>
> ________________________________
>
> From: talk-transit-bounces at openstreetmap.org
> [mailto:talk-transit-bounces at openstreetmap.org] On Behalf Of Brian Prangle
> Sent: 01 April 2009 13:41
> To: Talk-gb-westmidlands at openstreetmap.org; talk-transit at openstreetmap.org
> Subject: [Talk-transit] NaPTAN bus stop database import - some
> moreobservations
>
>
>
> Some more views and observations  on the NaPTAN data import in Birmingham:
>
> 1.       It serves as a great QA on OSM data and shows that in the City
> Centre where we have not been able to get decent GPS traces more accuracy
is
> needed so the potential of obtaining aerial photography is great.
>
> 2.        It’s a great impetus to resurvey streets where earlier work
> (potentially inaccurate from NPE tracing, older GPS devices, less points
> collected,  inexperience, not realising that roads have a width greater
than
> the rendered line so placing bus stops too close to the road etc.) can be
> improved.
>
> 3.       It’s also a great impetus to improve practice on surveying bus
> stops and be much more precise and comprehensive – also a stimulus to edit
> all those old bus stops where we placed them as a node on the way rather
> than to the side of ways which is our current practice.
>
> 4.       QA works both ways and our surveys should help to improve NaPTAN
> data.
>
> 5.       As an exercise(excuse the pun!) I cycled from Acocks Green to
> Moseley and back this morning along the No 1 bus route and surveyed 47 bus
> stops each time standing at the pole(leaning against it – you can’t get
> closer than that!)  or underneath the plate at a shelter:  4 bus stops
> coincided within 3-4 m; 17 were “good enough” coinciding <8-10m. That’s
> approx 45%. The rest were out by anything up to 90m or were just missing.
>
> 6.       I think either the pole where there is no shelter or the bus stop
> plate at a shelter should be what we survey – that’s where the
> identification of what we survey is located
>
> 7.       Where a physical stop on one side of the road doubles up for one
on
> the other side also – I think we’re OK by surveying and tagging the
physical
> one with Andy’s suggestion of a tag opposite=yes. The NaPTAN untagged node
> on the other side can be left in place to indicate the  logical
> relationship.
>
> 8.       I like the idea of tagging where the bus stop is set back in a
> “lay-by” from the road which might account for some NaPTAN nodes being
some
> distance from the road
>
> 9.       For our purposes “good enough” is probably sufficient rather than
> precise positional detail – I’m of the view that as long the bus stop has
> more or less the right relationships to its surroundings then that’s OK.
>
> 10.   Surprised that there is no data for either the closed Digbeth Coach
> Station which is being rebuilt or the temporary replacement nearby. I
> thought we were importing off-street bus stops? Perhaps the NaPTAN data
> doesn’t exist?
>
> 11.   Can’t find any nodes for  taxi ranks – not imported or doesn’t exist
> for Birmingham or I’m not looking hard enough?
>
> 12.   For the few nodes where I’ve estimated the fit between OSM and
NaPTAN
> to be “good enough” I’ve merged the nodes deleting the unverified tag and
> editing source tag to v=naptan_import;survey
>
> 13.   Verifying the data is going to be a long, slow process with a lot of
> resurveying needed.
>
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>
>



-- 
Regards,
Thomas Wood
(Edgemaster)