It is very difficult, and perhaps impossible, to measure a person's velocity directly using the GY-80. For an explanation, see this: http://www.chrobotics.com/library/accel-position-velocityHowever, it is possible to use an accelerometer to determine the gait (for example, time between footsteps) and using other information, to estimate a walking or running speed.
is it fine if you just measure the distance and possibly speed of the person using a gps shield???also try a modified pedometer system which could multiply the number of steps a person took with average calories burnt per step. there are various systems you could use but only if you are willing to change your basic design.
um...some one told me that to use to v=u+at to estimate the velocity, so is it applicable?
May I ask for the reason?
That is not currently possible with hobby-grade accelerometers, magnetometers and rate gyros.