I'm quite surprised that nobody has made an app which can do some baseline calibration and produce real-time current measurements yet; it would just be a few hundred lines of code at most.
(Fun fact: this is another project that Sebastian Staacks of http://there.oughta.be worked(s?) on. You might remember his wooden Gameboy shell, the Gameboy interceptor to screenshare the Gameboy screen to a PC or his bullettime video booth.)
That surprises me. As soon as a sensor saturates, you can no longer use it for dead reckoning (integrating the acceleration values to know position).
13g is way below what you'd expect when tapping the phone against a solid object for example - that could easily reach 1000g briefly.
I was under the impression that a big part of iphone's superior GPS performance was down to the clever use of dead reckoning and re-calculating past datapoints in a way android manufacturers rarely do.
Big g-forces are bad if experienced for more than a few hundred microseconds. But very briefly, they aren't too damaging.
Instead I think the iPhone cheat a bunch, and use a mixture of step counting, magneto and gyro inputs to perform dead reckoning. The iPhone uses periods when you GPS is in use anyway to calibrate your stride length at different speeds, which when mixed with magneto data to estimate a course direction, would allow an iPhone semi-accurately perform dead reckoning, without needing high resolution, wide scale, accelerometer input.
In short, the iPhone cheats. It’s dead reckoning systems take advantage human bio-mechanics to simplify the problem of dead reckoning, at the cost of building a dead reckoning system that only works effectively in a handheld device that semi-permanently lives on your person. A perfectly reasonable assumption for a phone, but a terrible solution for a more generic dead reckoning system.
It’s not even easy to find. Few months ago I wanted a simple audio spectrogram app, downloaded some which wanted dubious in-app purchases, or had ads. I hadn’t come across it earlier, but Phyfox does what I wanted better and for free.