Decimation of motion
Use predictive coding. If your predictor manages to guess current position based on previous recorded positions with reasonable accuracy — you can omit the recording of current position. Same predictor will also help you to reconstruct the original path.

What predictor you should use is based on the tracked object's nature. You may use a Kalman filter for example. Or you may use something really simple such as 'assume object always stays at the same place. If we are moving — record it'. Or 'assume object always travels along the straight line', etc.

If your predictor will do a good job, you can additionally use Huffman coding — small corrections of prediction errors will have shorter bit sequences, significant corrections — longer bit sequences. It will save you a huge amount of space with near-to-perfect reconstruction.