For a while the Tyne & Wear Metro have had scrolling matrix displays installed in their trains, but until this morning I hadn’t seen them switched on. On my commute to work today Nexus (the operators of the Metro) obviously had them in some kind of test mode, constantly scrolling the message “NEXUS METRO agps-bgps” as you can almost see on the rather rubbish photo below (it was moving text on a moving train and a phone camera, so it was bound to be bad):
Something like that isn’t going to pass me by without a fair amount of curiosity.
Obviously they are going to be showing information based on the location of the train – that makes sense if the information is going to be useful. AGPS (Assisted GPS) is something that I know about – devices use data from a mobile (cellular) network to achieve a faster location fix from GPS satellites – but BGPS was a new one on me, so I looked it up.
Ordinarily I would expect there to be an article, or at least a mention in a bigger article, about something like this on Wikipedia, but I didn’t see it. Instead I had to rely on a 2008 article from GPS World called Innovation: First AGPS – Now BGPS. It’s a long article and assumes a knowledge of GPS that I don’t have, but I’m pretty sure I understand the main points.
BGPS (named simply because B comes after A), is an adaptation of AGPS which gets round some of the limitations of AGPS. The Metro has underground sections, which do have some mobile network coverage, but obviously don’t have line of sight with satellites, and when a train is in the great outdoors, it probably doesn’t want to be reliant on mobile network coverage anyway – I know from experience that it’s not great.
BGPS allows the side loading of the data that would come from the mobile network by using some other means. This is perfectly reasonable on the Metro network which is both tightly defined and linear, so beacons at some or all stations, or at signals, could talk to the BGPS hardware on the train and tell it where it is and the precise time; two things that enable a quick GPS fix via communication with the satellites, and could possibly enable the train to know where it is without the satellites with a good degree of accuracy too.
It all sounds incredibly sensible, so I hope that Nexus put the technology to good use. I’m certainly looking forward to seeing what they do with it.
While I’m talking about the Metro, if there’s anyone reading this who is a regular Metro user and has an iPhone, I’d suggest you buy the incredibly useful Next Metro app. It tells you when the next train is due on your route so you know whether you need to run or can just saunter to the station. I hope they bring out an Android version soon!