How to Track Foot and Wrist Relative Position Outdoors With 2cm Accuracy for Sports?

I would like to create a device that tracks the position of the feet relative to the wrist. This is to be used outdoors for people that play sports and it is to be confined within an area of 15x30 meters. The idea is for specific times, not continuously, know the relative position of the wrist to the two feet within an accuracy of a couple cm. The horizontal position is very important, the vertical one less important. The orientation of the feet and wrist is also important to know. Any ideas how can that be accomplished? Would inertial measurement units work or other technology is needed?