Question about realtime train positions source


#1

Hi,

I’ve been looking at the vehicle positional data for sydney trains recently, and I was wondering where exactly the data comes from (I couldn’t find this information anywhere, I may have missed something)

I’m mainly curious because the accuracy of the coordinates seems to vary quite a lot over a single journey, sometimes being directly in the middle of a track, sometimes slightly off to the side, at stations the position is sometimes reported as being at a point in the middle of the station somewhere, but sometimes at a specific platform (They seem consistent with platforms at Central Station, for instance).

It would be useful for me to know how these coordinates are being generated.

For reference, I’ve been using this tool to analyse multiple coordinates at once: http://www.darrinward.com/lat-long/?id=2007932, so inaccuracies could be to do with that website. The data on that particular page is about 30 minutes of the 10:09 Central to Berowra service.


#2

OK I asked around internally where the data comes from… So this will be a placeholder answer until (and if!) I get a more official one.

There are a couple of data points. There is the data for the stops. This is generated by our (TfNSW) data team. Then there is the shapes data that is generated from an operational system (OSS) which feeds the rail control systems and track circuits. The locations and track circuits map to timetable geo nodes.

The short answer is the inaccuracy could be our data or can also be the website. The reference you sent looks pretty good (Central to Berowra) to me.

If the inaccuracy is 10m or less I think we can live with it, but if it’s a significant difference we’d be keen to get that data to do some tidy up. Feel free to post it here or PM me or email it to us.


#3

Cool, I was mainly just curious about the variance, but if it’s coming from different data-sets that makes sense. I’ll let you know if I come across anything substantially off.