Velocity is the velocity relative to the center of the body the launch site is on. On the ground at the pole, the velocity is zero. On the ground at the earth's equator, the velocity is the rotation boost, about four hundred and sixty meters per second. On a subsonic airliner at the earth's equator, the velocity is about seven hundred meters per second. The earth's low drag orbital velocity is seven thousand eight hundred meters per second. Given rotation boost and velocity components, the velocity is calculated.

velocity = sqrt( ( rotation boost + x velocity component )^2 + y velocity component^2 )
 

This is used in astropolis, spacecraft in vacuum, atmospheric spacecraft, multi stage spacecraft, and spacecraft cost.
 
 

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