ETA Drift Chart

Key point

planned, estimated, requested and actual times

One field often holds four kinds of time, and the newest record is not the best one. bestAvailable picks one and returns its class with it, so a column can say what it shows.

The four kinds are planned (PLN), estimated (EST), requested (REQ) and actual (ACT). The codes are the ones container shipping schedules use.

Drift is the last estimate minus the first. It exceeds a tolerance only when it is greater than it, in either direction. Drag the tolerance and watch exceedsTolerance change.

1. The timestamps

Three estimates of one vessel's arrival on 20 June 2024, recorded on 1, 5 and 10 June: 08:00, 12:00, then 17:00 UTC. The estimate moved 9 hours, more than the 8-hour tolerance. Drag the tolerance to exactly 9 hours: equal does not exceed.

Event 1

Class

PLN plannedEST estimatedREQ requestedACT actual

AtRecorded at

Event 2

Class

PLN plannedEST estimatedREQ requestedACT actual

AtRecorded at

Event 3

Class

PLN plannedEST estimatedREQ requestedACT actual

AtRecorded at

2. Which time, and how far it moved

Across: when each record was recorded. Up: the time it names, later at the top.

Tolerance optionalDrag the tolerance8 h024 h

3. What the calls return

 

 

Worth trying: an estimate recorded after the actual marks the actual as the best available. The late estimate is the naive pick: what you get by taking the newest record. Then a tolerance of exactly 9 hours: the drift is 9 hours, equal does not exceed, and exceedsTolerance is false.

Reference: bestAvailable and estimateDrift are the two calls behind every reading here. See the guide’s timestamp class section and its drift section, and the scenario An Estimate Shown as the Actual.