I’ve been monitoring the real time positions of trains from Sydney Trains and noticed at times the positions jump inconsistently.
Given that the data refreshes every 15 seconds, I would expect a smooth distance progression for a cruising train between stations but often I see the position remains stuck at one point for several intervals then jumps several blocks ahead at once.
So here are my questions,
Specifically for trains, where do you source the positioning data from? is this from the in-built GPS receivers inside each train? or only from the information obtained from the occupation of the ‘track circuits’? or perhaps combination of the two?
If the source is from the track circuits (think I saw a thread mentioning this earlier…) then as far as I know the lengths of the track circuits vary depending on the signalling requirements, for a long track circuit (e.g. 500~600 meters long), how do you report the train position? For example, while the train is occupying the track circuit, you would not know where the train is within that track circuit block, then do you report the train being at the beginning of the block? or middle or the end?
Are there any plans on improving the quality of the trains positioning data? (e.g. use of more accurate GPS receiver, higher update frequency, etc.)
Thanks a lot,