I wanted to use the raw data from my iPhone accelerometer to track displacement. I downloaded an app called Accelerometer Data Pro. It is pretty fun. You slide a bar to start sampling, walk around the room, and then slide the same bar to stop sampling. The time series results can then be downloaded to your computer in csv format.
I tried using the simple equations of motion in an Excel spreadsheet to convert accelerations into displacements, but there is so much noise. I did a test where it picked up the phone, walked around, and placed it back in the same spot. I set the origin to be the original resting place of the unit. If everything worked correctly, I hypothesized, then I should be able to plot a path that curves around in space, and then returns back to the origin. ...That didn't happen.
I was wondering if anyone else had every played around with similar accelerometer data. What tricks did you use to filter out the noise in the data? Also, how did you subtract out the acceleration of gravity. Unless I hold the phone perfectly level, it is hard to differentiate the accelerations from motion, from gravity. The iPhone doesn't have gyros, so it is difficult to determin the orientation of the device at each data reading.