On Mon, Nov 29, 2010 at 12:36 PM, [email protected] <[email protected]> wrote: > > To calculate velocity from acceleration I'd like to use Euler integration
Euler integration can be unstable. I wouldn't discount it right away, but you might see artifacts in your velocity calculation. > I cannot assume that the application is started exactly when a person starts > to > move, so the initial velocity will most certainly not be 0 but can be > anything. Correct. However, absolutely uniform motion is an unrealistic ideal in most terrestrial situations: you move, you vibrate in some way. If the accelerometers are measuring very little (close to zero) acceleration, and they stay that way for some amount of time (several seconds), you can assume the phone velocity is essentially zero. An integrator is likely to `drift' over time. In theory, when you stop moving you should have to apply exactly the same acceleration in reverse from when you started. In practice, however, the two accelerations won't quite cancel (there will be errors in measurement and error accumulation in the integrator). You'll have to re-zero the integration every now and then to keep it at a sane value. Alternatively, you could use GPS or some other position data to supply an upper bound on the velocity and acceleration and then try to correct the integration that way. In any case, this is an officially difficult problem which has no known `solution'. You're going to learn a lot! -- ~jrm _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
