If I am walking, the ground is stationary, and I move X units/hour relative to the ground.
If I am in low-earth orbit, then I am still moving X units/hour relative to the ground, only its a much bigger X.
If I am in geo-stationary orbit, I am moving 0 units/hour relative to the ground. But relative to the axis of the earth, I am moving as fast as the earth spins. So am I moving at 0 units/hour or the speed of the earth's rotation (plus a little since its away from the surface)?
If I go to the moon, the earth will be rotating so my speed would have to be relative to the distance from the axis of the earth, and not the position around the axis like in geo-stationary
Now imagine I am leaving earth's orbit, my speed can't be measured relative to the distance I am from the earth's axis because it's moving around the sun. So at what point does my speed change from being relative to earth to being relative to the sun and is there a spike in the numbers from this transition?
I guess I am confused because from everything I read and hear about spacecraft, the speed is always brushed over like its really obvious and intuitive. But I don't really think it is.