Differences between showing actual/real-time location of vehicle between OneBusAway and TransitClock

[wkulesza]

Hi,
could someone shine some light on how does OBA how actual/real-time location of vehicle. When comparing data coming from TransitClock and OneBusAway, one can observe differences in vehicle location - it seems TC is always using real-time and actual location, while OBA uses some predicted method, sometimes as far as 2,5km away from actual position.
I will try to add screenshots, when we catch such situation, but in the meantime, could anyone confirm/deny and point to the place in code?

[wkulesza]

Here you can see around 1km - which could potentially be related to frequency of getting data (15secs each system), but we could see 2,5km differences with good knowledge that there were no breaks in internet connection on GPS devices.