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I'm looking at building a smartphone app that will need to track the users limbs (say legs/feet) as accurately as possible. The goal is to trace the moments of body parts and the timing of the movements in relation to each other.

I'm more of a computer science guy than an electrical engineering guy and am not quite sure how to do it. How realistic it is.

There seems to be a similar question here: Sensor for hand/foot location in relation to a persons body

Is seems to make senses as far as distance is concerned but I need direction as well.

I was think accelerometers might be worth looking at but how accurate are they and do they need to be calibrated often? For example if the accelerometers were on a persons feet would they have to stand with their feet together to calibrate and then you would be able to work out new locations based on their movements from the calibrated position?

Bluetooth proximity sensors seem to only tell distance and not direction and don't look to be accurate enough.

Any ideas?

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    \$\begingroup\$ Very, very unrealistic. There simply isn't enough information available from the sensors in a smartphone (no, not even with the camera). \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 7 '13 at 5:02
  • \$\begingroup\$ Sorry I was thinking external sensors that send back information to the smartphone say via bluetooth. Sorry I should have made myself clear. Thanks. \$\endgroup\$ – betaass Aug 7 '13 at 5:26
  • \$\begingroup\$ Distance-based triangulation in n dimensions requires n+1 sensors. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 7 '13 at 5:59
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An accelerometer/Gyro sensor (Accelerometer for the static angle and gyro for the dynamic angular movement) would be great for such an application, however each limb will require one such node. ST and Freescale both have such sensors, often called 6D.

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  • \$\begingroup\$ thanks! Is my thinking right, that you would have to calibrate it by for example getting the user to stand with their feet together and then calculate movements from there? \$\endgroup\$ – betaass Aug 7 '13 at 8:02
  • \$\begingroup\$ The only calibration in my opinion would be the limbs lengths. The rest can be calculated via forward Kinematics and inverse kinematics. \$\endgroup\$ – Lior Bilia Aug 7 '13 at 10:04
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Ultra Wideband (UWB) technology is known to provide resolution in millimeters. UWB can even detect respiratory chest movements of human beings.

"UWB signals provide features such as low energy consumption, low electromagnetic radiation, low interference, and the ability to penetrate obstacles, including concrete. These features lead to many potential applications including medical instrumentation, search and rescue, security and surveillance, and indoor tracking and localization to name a few".

For more information visit the following link:

https://innovation.kaust.edu.sa/technologies/low-complexity-ultra-wideband-uwb-sensor-for-wireless-detection-and-monitoring/

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