Friday 21 August 2009

Bus stops

Much of the data in the database for the UK were gathered either by tracing out-of-copyright maps or gathering GPS traces with notes or photos to add the detail. We do have some imported data though and NaPTAN is one. The National Public Transport Node database which has data gathered from local authorities about things like bus stops. A selection of the data was loaded for the West Midlands to trial and now the data for Hull has been loaded. We set out today to see how easy it is to verify.

It was pouring with rain when we decided to go, so we went in the car. This was our first mistake. Next time I'm going by bike. You need the bike to cover the ground between the stops, but you need to be able to stop at a bus stop, to take a photo and a GPS way point. The car was just a nuisance. The next mistake was to not check the camera battery before we set off; it promptly gave up after four pictures, one of which was the photo of the GPS to sync the times up. We then resorted to keeping a list and using GPS way points. This meant getting right next to the bus stop to establish its position.

The NaPTAN data loaded has made many tags, including a code, the street name the stop is on, a name for the stop and other location stuff like a street that is nearby. Part of the code is displayed on the bus stop sign. All of this seems fine, until you discover a bus stop that is not where it's supposed to be. We found a stop on Sibelius road but the ID was for one described as on the nearby Gershwin Avenue. One of the tags is a bearing to help understand the direction that the bus would go from the stop, such as N (north) or SW (south west). The bearing for the stop was N but the stop faced west. I moved the stop to reflect its real position, but should I change the NaPTAN tags? I've asked the talk-transit mailing list what they think, but the more I think about it the more I think that the imported data should remain. Maybe our findings should get fed back to the authority that created the NaPTAN data and amend them.

I think the whole exercise will take ages to complete, but it will be a background task to fit in around other things. A few other things will make the process easier. Firstly I need a render of the map that shows the bus stops but more zoomed out than the standard renders which only show them at zoom 17. I also need to process the bus stops to produce a list we can work from. I downloaded the OSM changeset of the upload to work from so I'll process that into some sort of list. This process might be useful to other people who follow with all of the other areas of the UK.

1 comment:

milliams said...

Have you seen ? It's designed for making the NAPTAN import/merging easier.

Also, I wish that there was a simple guide on the wiki for "what to do once the NAPTAN data is imported into your area" since at the moment there's just too many pages which are all in a bit of a jumble.