> Usability of apple iPhones for inertial navigation systems. - ResearchGate
to quote from the full text of the paper:
"Fluctuation and jitter contribute to the inaccuracy and make an exact determination of the velocity and the position difficult. Due to the necessity of filtering the data stream, further losses of information arise and increase over time. [...]
However, the tests show that even with the use of filters it is challenging to build a precise INS using sensors from common devices because of their inaccuracies and high error rate.
The results show that the iPhone 4 can provide tolerable results for a short time, but then the deviation becomes too high because of the error rate."
Or consider this... the accelerometers and gyros are designed and optimized for mass market consumer applications (read: mobile devices) in terms of application, technical specification and - most important - cost, which is typically less than $1 for each sensor. (My company works in this field.)
Any IRS application most likely needs sensors build to different specifications, at a different cost. Or, to quote the paper again, "By examining the raw accelerometer data of the iPhone 3GS and iPhone 4, it becomes clear that low-cost MEMS are used in both."