The estimated time of arrival or ETA (sometimes called ETOA) is a measure of when a ship, vehicle, aircraft, cargo, emergency service or computer file is expected to arrive at a certain place. One of the more common uses is in public transportation where the movements of trains, buses, airplanes and the like can be used to generate estimated times of arrival depending on either a static timetable or through measurements on traffic intensity. In this respect, the phrase or its abbreviation is often paired with its complement, "estimated time of departure" or "ETD", to indicate the expected start time of a particular journey. This information is often conveyed to a passenger information system as part of the core functionality of intelligent transportation systems.
For example, a certain flight may have a calculated ETA based on the speed by which it has covered the distance traveled so far. The remaining distance is divided by the speed previously measured to roughly estimate the arrival time. This particular method does not take into account any unexpected events (such as new wind directions) which may occur on the way to the flight's destination.
ETA is also used metaphorically in situations where nothing actually moves physically, as in describing the time estimated for a certain task to complete (e.g. work undertaken by an individual; a computation undertaken by a computer program; or a process undertaken by an organization). The associated term is "estimated time of accomplishment", which may be a backronym. For example, Bittorrent clients specify ETA as the expected time remaining for a file to completely download as 1d4h (1 day and 4 hours), 1w2d (1 week and 2 days), etc.
Accurate and timely estimations of times of arrival are important in several application areas:
In air traffic control arrival sequencing and scheduling, where scheduling aircraft arrival according to the first-come-first-served order of ETA at the runway minimizes delays.
In airport gate assignment methods, to optimize gate utilization.
In elevator control, to minimize the average waiting time or journey time of passengers (destination dispatch).
Several patents have been issued for methods or devices for calculating estimated times of arrival, including:
US patent 2646924, Oscar Hugo Schuck, "Computer for estimated time of arrival", issued 1948-11-29
US patent 3443073, Richard L. Cohen, "Groundspeed and estimated time of arrival computer", issued 1969-05-06
US patent 3619579, Earl Stuart Perkins, "Time of arrival and ground speed computer", issued 1971-10-28
US patent 4012900, Wayne Jay Enright, "Setting means for estimated time of arrival clock hands", issued 1977-03-22
US patent 4153874, Erwin A. Kaestner, "Mobile perpetually self-correcting estimated time of arrival calculator", issued 1977-05-08
US patent 5570100, Gary W. Grube, Mark C. Naddell, Mark L. Shaugnessy, "Method for providing a communication unit's estimated time of arrival", issued 1996-10-29
US patent 5742635, H. Britton Sanderford, Jr., "Enhanced time of arrival method", issued 1998-04-21
US patent 5764686, H. Britton Sanderford, John R. Souvestre, "Enhanced time of arrival method", issued 1998-06-09
US patent 6144917, Thomas H. Walters, Darin J. Beesley, Stephen C. Robinson, "Calculation of estimated time of arrival (ETA) based on thoroughfare classification and driving history", issued 2000-11-07
US patent 7212975, David Frederick Bantz, Steven J. Mastrianni, "Apparatus and methods for providing an estimated time of arrival based marketplace", issued 2007-05-01
US patent 7457195, Robert Hughes Jones, "Estimating the time of arrival of a seismic wave", issued 2008-11-25
US patent 7536321, Shinichi Takahashi, Takenari Kawano, Kazuo Tsugu, Ken Nishioka, "Estimated time of arrival (ETA) systems and methods", issued 2009-05-19
US patent 6370231, Janice Paris Hice, "Method and system for calculating the estimated time of arrival of a service technician", issued 2002-04-09
US patent 6469665, Domenico G. Porcino, "Time of arrival estimation positioning systems", issued 2002-04-12
US patent 6675018, Eric Villier, Luis Lopes, Brendan Luddon, "Method of and system for estimating a time of arrival of a radio signal", issued 2004-01-06
US patent 8165792, Jeffrey Clinton Mikan, Justin McNamara, John Ervin Lewis, Fulvio Arturo Cenciarelli, "Methods and systems for broadcasting an estimated time of arrival", issued 2012-04-24
