[potatolicious]

> "It's just from my experience you can't calculate displacement using an accelerometer that cheap "

I disagree. You clearly can - the app and the people who use it are proof positive of the sensor's capabilities. Having seen the raw output from these sensors a few times they're also startlingly accurate.

The problem is of course that it's not simple and there's real complexity in the solution. It's (of course) impossible if you blindly take the double integral of raw accelerometer readings.

In the same way we do all kinds of magical things with all kinds of sensors - but it's rarely as simple as plugging a pin into a ADC and reading the bits that come out.

Signal processing, in both hardware and software, is a gigantic field of study unto itself. I fully expect that the app is doing something non-trivial with its sensor readings to gain accuracy - but it's eminently possible, just difficult.

The intersection of "mobile app developer" with "skilled signals engineer" is pretty low. If someone capable wrote a library that did this, you'd bet that we'd see an explosion of apps that use this functionality.

[mojuba]

So you've seen raw output from the accelerometer and you think they were fine, but do you realize that the error gets cubed when you calculate displacement from those values?