Greenwich True of Date Coordinate System

The position of the Space Shuttle is specified by the Greenwich true of date (GTOD) (geographic) coordinate system. The GTOD system is a rotating, right-handed, Cartesian system with the origin at the center of the Earth. The orientation of this system is specified with:

• The XY plane is the Earth's true of date Equator.
• The Z axis is directed along the Earth's true of date rotational axis and is positive north.
• The positive X axis is directed toward the prime meridian.
• The Y axis completes a right-handed system.