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I am working on an application where I would like to track the position of a mobile user inside a building where GPS is unavailable. The user starts at a well known fixed location (accurate to within 5 centimeters), at which point the accelerometer in the phone is to be activated to track any further movements with respect to that fixed location. My question is, in current generation smart phones (iphones, android phones, etc), how accurately can one expect to be able to track somebodies position based on the accelerometer these phones generally come equip with?
Specific examples would be good, such as "If I move 50 meters X from the starting point, 35 meters Y from the starting point and 5 meters Z from the starting point, I can expect my location to be approximated to within +/- 80 centimeters on most current smart phones", or whatever.
I have only a superficial understanding of techniques like Kalman filters to correct for drift, though if such techniques are relevant to my application and someone wants to describe the quality of the corrections I might get from such techniques, that would be a plus.
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Typical phone accelerometer chips resolve +/- 2g @ 12 bits providing 1024 bits over full range or 0.0643 ft/sec^2 lsb. The rate of sampling depends on clock speeds and overall configuration. Typical rates enable between one and 400 samples per second, with faster rates offering lower accuracy.
Accelerometers can be used to make very accurate pedometers that can measure walking distance to within ±1%.
Because they can accurately determine the speed, direction and position of a body in motion, accelerometers play an indispensable role in providing digital electronic circuits with real-world information for a multitude of applications.
Devices differ in accuracy with some showing mean deviations close to 0° and little variance while other devices show mean inaccuracies of up to 2°, on some occasions reaching over 6° compared to the objective tilt. The deviations are higher for measurements of roll than they are for measurements of pitch.
If you integrate the accelerometer values twice you get position but the error is horrible. It is useless in practice.
Here is an explanation why (Google Tech Talk) at 23:20.
I answered a similar question.
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