Ultra Wide Band (UWB) provides ranging capabilities much more precise than other radio communication technologies. This paper presents experimental measurement of ranging precision between two UWB tags when one of the tag is moving fast. The use of a specific electro-pneumatic actuator provides precise ground truth for real distance. This study will allow to improve ranging for human wearable tags as for example sportsmen positionning or interaction between dancers during live performances. We show in particular how the inherent noisy measurement has to be smoothed to obtain more acurate ranging.