Representations of time coordinates in FITS - Time and relative dimension in space

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Table 4

Compatibility of time scales and reference positions¹.

Reference	TT, TDT	TCG	TDB	TCB	LOCAL
Position	TAI, IAT
	GPS
	UTC, GMT

TOPOCENTER	t	ls
GEOCENTER	ls	c
BARYCENTER			ls	c
RELOCATABLE					c
Other²	re	re

Notes.

⁽¹⁾

Legend (combination is not recommended if no entry): c: correct match; reference position coincides with the spatial origin of the space-time coordinates, t: correct match on Earth’s surface, otherwise usually linear scaling, ls: linear relativistic scaling, re: non-linear relativistic scaling.

⁽²⁾

All other locations in the solar system.

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