State vector (geographical)
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A geographical state vector is a set of data describing exactly where an object is located in space, and how it is moving. From a state vector, the object's current and future position can be determined.
A geographical state vector typically will contain seven elements: three position coordinates, three velocity terms, and the time at which these values were valid.
A state vector may be expressed in a variety of coordinate systems. Selection of a coordinate system depends on what makes sense for the problem being solved. In aviation, a state vector may be expressed in the North, East, Down coordinate system, where North position is expressed as a latitude, East position as a longitude, and Down represents the inverse of altitude. (Down is used instead of Up to conform to the right-hand rule. The velocity components of the state vector would be North velocity, East velocity, and vertical speed.
