# State Vectors

*State Vectors* are *Cartesian*
coordinates
describing the position and velocity, or *state* of a satellite. As with
the
keplerian elements,
6 basic coordinates are required to fully specify the position at a given
epoch.
The first 3 values are the position in a right-angled
coordinate system
(X, Y, Z, for *inertial* coordinates (*ECI coordinates*), or E, F, G
for earth-based, or *geodetic* coordinates (*EFG coordinates*). The
next three values (with "dot" denoting the *time derivative*) are the
corresponding *velocity components*.

The NASA *Earth Fixed Greenwich - EFG* coordinate system rotates with the
earth (hence it is not *inertial* or fixed in space, but undergoes
motion). The velocities in this coordinate system are reduced by the
rotational velocity of the earth.

State Vectors can be use in place of
Keplerian Elements
as a source of information for the
Satellite Database
in **WinOrbit**. See the discussion of
*.VEC files.

State Vectors can be displayed from the **Map Window**
Function Menu.