Re: [Talk-transit] NaPTAN bus stop database import - some moreobservations
Brian Good comments - and from my NaPTAN perspective I share your view that data improvement should be a two-way thing. I am very keen to see if we can make that work through this exercise. I have always said that linear positioning of bus stops can be good enough if it is +/- 10m given that a bus is typically 12m long. But if it can be more precise than this, so much the better. Lateral displacement is more serious from the mapping perspective - and therefore the tolerance probably in both directions has to be set rather lower. Strangely at about the same time as you sent your message, one of my colleagues researching something completely different through the traveline journey planners, also commented on issues to do with the incorrect representation of Digbeth in NaPTAN data. My quick assessment is that neither the old nor the current coach stations have a NaPTAN record - and what has been happening without anyone realising it is that coaches have been shown on journey planners to be going to and from a particular roadside stop in the area of the old coach station. I have asked someone to investigate this and get it resolved in NaPTAN in the near future. 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? Best wishes Roger _ From: talk-transit-boun...@openstreetmap.org [mailto:talk-transit-boun...@openstreetmap.org] On Behalf Of Brian Prangle Sent: 01 April 2009 13:41 To: talk-gb-westmidla...@openstreetmap.org; talk-transit@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. ___ Talk-transit mailing list Talk-transit@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-transit
Re: [Talk-transit] NaPTAN bus stop database import - some moreobservations
I've just done a quick render of what was extracted from the West Mids data set - http://dev.openstreetmap.org/~edgemaster/naptan/ 2009/4/1 Roger Slevin ro...@slevin.plus.com: 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.edgemas...@gmail.com] Sent: 01 April 2009 18:15 To: ro...@slevin.plus.com Cc: Brian Prangle; talk-gb-westmidla...@openstreetmap.org; talk-transit@openstreetmap.org Subject: Re: [Talk-transit] NaPTAN bus stop database import - some moreobservations 2009/4/1 Roger Slevin ro...@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-boun...@openstreetmap.org [mailto:talk-transit-boun...@openstreetmap.org] On Behalf Of Brian Prangle Sent: 01 April 2009 13:41 To: talk-gb-westmidla...@openstreetmap.org; talk-transit@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. ___ Talk-transit mailing list Talk-transit@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-transit -- Regards, Thomas Wood (Edgemaster) --
Re: [Talk-transit] [Talk-gb-westmidlands] NaPTAN bus stop databaseimport - some moreobservations
Roger Slevin [mailto:ro...@slevin.plus.com] wrote: Sent: 01 April 2009 8:18 PM To: 'Andy Robinson (blackadder-lists)'; 'Brian Prangle'; Talk-gb- westmidla...@openstreetmap.org; talk-transit@openstreetmap.org Subject: RE: [Talk-transit] [Talk-gb-westmidlands] NaPTAN bus stop databaseimport - some moreobservations Andy Useful assessment of a small group of records - thanks for making it available. I looked at the first one of the ones you said was not represented on the road ... looking at the NaPTAN data the stop is classed as CUS which means Custom and practice - or in other words, unmarked. You comment that it appeared to be unused - and my quick check of the West Midlands traveline journey planner seems to confirm that this is likely to be the case. I think it would have been used at some time in the period since traveline began in 2000 ... but in NaPTAN the ACTive status of a record does NOT mean it is in use, it simply means that it is available to be used. This is fundamental to NaPTAN which is only a location database - it is not influenced directly by the existence of services. Of course it would be possible for Centro to designate the stop as inactive ... but there is no obligation on them to do so, and most authorities will only do that in situations where a stop is taken out of service permanently (maybe for safety reasons, or changes in adjacent development). I hope this is a useful insight into the context of at least some of your comments. It is, thanks. It reinforces the need to separate out within OSM that data which is current and relevant and that which is fanciful. The latter can stay in but needs to be properly flagged as inactive. Since OSM is a wiki anyone can reactivate a node at a later date. BTW, Thomas has just imported West Bromwich (not many stops) ready for our mapping party at the weekend. We will discuss the rest of the west mids at our social tomorrow evening. Cheers Andy Best wishes Roger -Original Message- From: talk-transit-boun...@openstreetmap.org [mailto:talk-transit-boun...@openstreetmap.org] On Behalf Of Andy Robinson (blackadder-lists) Sent: 01 April 2009 19:40 To: 'Brian Prangle'; talk-gb-westmidla...@openstreetmap.org; talk-transit@openstreetmap.org Subject: Re: [Talk-transit] [Talk-gb-westmidlands] NaPTAN bus stop databaseimport - some moreobservations As promised my review of a further 50 bus stops in Sutton Coldfield. See the linked PDF [1] for full analysis. 50 locations evaluated in Sutton Coldfield. All stops except one in the NaPTan database and the one that wasn't is an unused shelter in a row of shelters in the centre of town so probably isn't in the NaPTAN dataset anyway. Of the remaining 49, 13 (27%) have no physical presence on the ground and in most case have never been used as a stop as far as I know. The average positional error from my survey was 13.7m with a maximum of 84m and a minimum of 1.6m. One third were within 5m. The standard deviation was 16.84m. The majority of stops were logically positioned on the correct side of the road and where it was close I checked the road alignment and adjusted it to the GPS traces where appropriate. A small number of NaPTAN nodes were not in their logical positions, eg both stops of a pair on the same side of the street. The largest displacement values were all longitudinal displacements along the street. A question arises what to tag a NaPTAN stop that is not present on the ground. I've used for now physically_present=no. These stops also don't currently carry a highway=bus_stop tag. Cheers Andy [1] http://ajr.hopto.org/osm/NaPTAN.pdf -Original Message- From: talk-gb-westmidlands-boun...@openstreetmap.org [mailto:talk-gb- westmidlands-boun...@openstreetmap.org] On Behalf Of Brian Prangle Sent: 01 April 2009 1:41 PM To: talk-gb-westmidla...@openstreetmap.org; talk-transit@openstreetmap.org Subject: [Talk-gb-westmidlands] 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. Its 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. Its 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
