Estimated time of arrival
Encyclopedia
The estimated time of arrival or ETA 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 train
s, bus
es, airplane
s 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.
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 metaphor
ically 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.
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...
, vehicle
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
, aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
, cargo
Cargo
Cargo is goods or produce transported, generally for commercial gain, by ship, aircraft, train, van or truck. In modern times, containers are used in most intermodal long-haul cargo transport.-Marine:...
, emergency service
Emergency service
Emergency services are organizations which ensure public safety and health by addressing different emergencies. Some agencies exist solely for addressing certain types of emergencies whilst others deal with ad hoc emergencies as part of their normal responsibilities...
or computer file
Computer file
A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished...
is expected to arrive at a certain place. One of the more common uses is in public transportation where the movements of train
Train
A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...
s, bus
Bus
A bus is a road vehicle designed to carry passengers. Buses can have a capacity as high as 300 passengers. The most common type of bus is the single-decker bus, with larger loads carried by double-decker buses and articulated buses, and smaller loads carried by midibuses and minibuses; coaches are...
es, airplane
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...
s and the like can be used to generate estimated times of arrival depending on either a static timetable
Public transport timetable
A public transport timetable is a representation of public transport information to assist a passenger with planning a trip using public transport. A timetable details when vehicle will arrive and depart specified locations and may be organised for by route or for a particular stop...
or through measurements on traffic
Traffic
Traffic on roads may consist of pedestrians, ridden or herded animals, vehicles, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel...
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.
For example, a certain flight may have a calculated ETA based on the speed
Speed
In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...
by which it has covered the distance
Distance
Distance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, or an estimation based on other criteria . In mathematics, a distance function or metric is a generalization of the concept of physical 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 metaphor
Metaphor
A metaphor is a literary figure of speech that uses an image, story or tangible thing to represent a less tangible thing or some intangible quality or idea; e.g., "Her eyes were glistening jewels." Metaphor may also be used for any rhetorical figures of speech that achieve their effects via...
ically 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
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
; or a process undertaken by an organization). The associated term is "estimated time of accomplishment", which may be a backronym
Backronym
A backronym or bacronym is a phrase constructed purposely, such that an acronym can be formed to a specific desired word. Backronyms may be invented with serious or humorous intent, or may be a type of false or folk etymology....
. For example, Bittorrent
BitTorrent
BitTorrent is a peer-to-peer file sharing protocol used for distributing large amounts of data over the Internet. BitTorrent is one of the most common protocols for transferring large files, and it has been estimated that it accounted for roughly 43% to 70% of all Internet traffic .Programmer...
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.