Would you not be implicitly assuming that the prior position was more accurate than the current one? If you have a sequence of consistent prior positions, then

Would you not be implicitly assuming that the prior position was more accurate than the current one? If you have a sequence of consistent prior positions, then perhaps something like a Kalman filter would be appropriate, but I would guess that with something suddenly being revealed by a change in either party's position or that of a third party, you don't always have that.