Why are movement times sometimes predicted?

[phoenix1589]

Using sites like opentraintimes, I notice that a train will show an arrival/passing time very slightly in the future, when it hasn't yet entered the berth. Yesterday, an on time train showed as 5L in the future, and was then updated to be on time when it actually passed.

I can understand a slight delay in the train entering the berth to actually appearing in the data, but not having data that is predicted.

Does anyone know why this happens?

Also, what is the correct term for this 'movement time' ?

 

[zwk500]

Using sites like opentraintimes, I notice that a train will show an arrival/passing time very slightly in the future, when it hasn't yet entered the berth. Yesterday, an on time train showed as 5L in the future, and was then updated to be on time when it actually passed.

I can understand a slight delay in the train entering the berth to actually appearing in the data, but not having data that is predicted.

Does anyone know why this happens?

There is a thing called a 'Berth Offset' where the train has a predetermined amount of time added to it upon entering the Berth. This is because a train is considered to enter the next berth the moment it passes the protecting signal but may have to travel a significant distance until it stops/passes the actual TIPLOC point.
However something different appears to have happened with what you're describing and I don't know what this would be.

Also, what is the correct term for this 'movement time' ?

Reporting time.