How to measure the distance covered by iphone during free fall?

Question

During the free fall the iphone is supposed to send acceleration values as 0 on all the three axis. So how to detect the distance covered by the iphone?

Answer 1

Do not trust Newton laws, they ignore air drag, Iphone rotation etc. Use empirical approach instead. Let the device fall from several heights like 1m, 2m, 5m, 10m, 30m... Repeat several times for each height. In each fall measure time. Approximate results by spline. Compute inverse function.