The instant that the gravitational correction started to be applied serves as the epoch for Barycentric Coordinate Time ( TCB ), Geocentric Coordinate Time ( TCG ), and Terrestrial Time ( TT ).

Difficulties were recognized, which led to these being in turn superseded in the 1990s by time scales Terrestrial Time ( TT ), Geocentric Coordinate Time GCT ( TCG ) and Barycentric Coordinate Time BCT ( TCB ).

* Barycentric Coordinate Time

For the calculation of ephemerides, TDB was officially recommended to replace ET, but deficiencies were found in the definition of TDB ( though not affecting T < sub > eph </ sub >), and these led to the IAU defining and recommending further time scales, Barycentric Coordinate Time ( TCB ) for use in the solar system as a whole, and Geocentric Coordinate Time ( TCG ) for use in the vicinity of the Earth.

Barycentric Coordinate Time is a coordinate time scale at the center of mass of the solar system, which is called the barycenter.

* Barycentric Coordinate Time ( TCB ) is a coordinate time having its spatial origin at the solar system barycenter.

Practical examples include the International Atomic Time standard and its relationship with the Barycentric Coordinate Time standard used for interplanetary objects.

TDB is now ( since 2006 ) defined as a linear scaling of Barycentric Coordinate Time ( TCB ), and a feature that distinguishes TDB from TCB is that TDB, when observed from the Earth's surface, has a difference from Terrestrial Time ( TT ) that is about as small as can be practically arranged with consistent definition: the differences are mainly periodic, and overall will remain at less than 2 milliseconds for several millennia.

) After the difficulties were appreciated, in 1991 the IAU refined the official definitions of timescales by creating additional new time scales: Barycentric Coordinate Time ( TCB ) and Geocentric Coordinate Time ( TCG ).

Barycentric Coordinate Time ( TCB, from the French Temps-coordonnée barycentrique ) is a coordinate time standard intended to be used as the independent variable of time for all calculations pertaining to orbits of planets, asteroids, comets, and interplanetary spacecraft in the Solar system.

Barycentric Coordinate Time ( TCB ) is the equivalent of TCG for calculations relating to the solar system beyond Earth orbit.

In 1976 the IAU resolved that the theoretical basis for its current ( 1952 ) standard of Ephemeris Time was non-relativistic, and that therefore, beginning in 1984, Ephemeris Time would be replaced by two relativistic timescales intended to constitute dynamical timescales: Terrestrial Dynamical Time ( TDT ) and Barycentric Dynamical Time ( TDB ).

For practical purposes the length of the ephemeris second can be taken as equal to the length of the second of Barycentric Dynamical Time ( TDB ) or Terrestrial Time ( TT ) or its predecessor TDT.

It was the counterpart to Barycentric Dynamical Time ( TDB ), which was a time standard for Solar system ephemerides, to be based on a dynamical time scale.

* Barycentric Dynamical Time ( TDB ) is similar to TDT but includes relativistic corrections that move the origin to the barycenter.

Barycentric Dynamical Time is a dynamical time at the barycenter.

Barycentric Dynamical Time ( TDB ), a form of atomic time, is now used in the construction of the ephemerides of the planets and other solar system objects, for two main reasons.

The day was also redefined to be exactly 86400 SI seconds when measured at mean sea level on the Earth: in practice, it is measured in Barycentric Dynamical Time ( TDB ).

Barycentric Dynamical Time ( TDB ) is a relativistic coordinate time scale, intended for astronomical use as a time standard to take account of time dilation when calculating orbits and astronomical ephemerides of planets, asteroids, comets and interplanetary spacecraft in the Solar System.

* Barycentric coordinate system

The new time scale to supersede ET for planetary ephemerides was to be Barycentric Dynamical Time ( TDB ).

* Barycentric Dynamical Time, time standard

Motion of Barycentric coordinates ( astronomy ) | barycenter of solar system relative to the Sun.

TT was formally defined in terms of Geocentric Coordinate Time ( TCG ), defined by the IAU on the same occasion.

TT differs from Geocentric Coordinate Time ( TCG ) by a constant rate.

where TT and TCG are linear counts of SI seconds in Terrestrial Time and Geocentric Coordinate Time respectively, L < sub > G </ sub > is the constant difference in the rates of the two time scales, and E is a constant to resolve the epochs ( see below ).

The present definition of TT is a linear scaling of Geocentric Coordinate Time ( TCG ), which is the proper time of a notional observer who is infinitely far away ( so not affected by gravitational time dilation ) and at rest relative to the Earth.

* Geocentric Coordinate Time

Geocentric Coordinate Time is a coordinate time scale at Earth's center.

Coordinate systems fixed with respect to the rotating axles are defined as having their x-axis unit vectors ( and ) pointing from the origin towards one of the connection points.

Coordinate dimensioning was the sole best option until the post-World War II era saw the development of geometric dimensioning and tolerancing ( GD & T ), which departs from the limitations of coordinate dimensioning ( e. g., rectangular-only tolerance zones, tolerance stacking ) to allow the most logical tolerancing of both geometry and dimensions ( that is, both form and sizes ).

Coordinate data from ACME Mapper.

* A nearly official Coordinate Reference System Registry from the OGP, Oil and Gas Producers Association

:: Coordinate conjunction ( C ), determiner ( D ), negation ( Neg ), particle ( Par ), preposition ( P ) and prepositional phrase ( PP ), subordinate conjunction ( Sub ), etc.

# Coordinate containing degrees ( integer ), minutes ( integer ), and seconds ( integer, or real number ) ( DMS ).

In the two Cabinets of Paavo Lipponen ( 1995 – 2003 ), Siimes served as the Coordinate Minister for Culture ( 1998 – 1999 ) and as the Minister of Finance ( 1999 – 2003 ).

Coordinate sheets are set up as a list of the member's places on the field, given in coordinates ( such as 5 steps inside the right 45 yard line and 2. 25 steps in front of the Home hash ), each " set " numbered.

The Coordinate system # Coordinate surface | coordinate surfaces of the Cartesian coordinates ( x, y, z ).

* Geocentric Coordinate Time ( TCG ) is a coordinate time having its spatial origin at the center of Earth's mass.

* Display Coordinate System, the coordinate system where objects are transformed to before being displayed in CAD systems.

Geocentric Coordinate Time ( TCG-Temps-coordonnée géocentrique ) is a coordinate time standard intended to be used as the independent variable of time for all calculations pertaining to precession, nutation, the Moon, and artificial satellites of the Earth.

Coordinate descent does a line search along one coordinate direction at the current point in each iteration.