[racket] what initial velocity to use when calculating velocity from acceleration (peripherally moby-related...)

From: Jakub Piotr Cłapa (jpc-ml at zenburn.net)
Date: Mon Nov 29 15:53:31 EST 2010

On 29.11.10 21:36, keydana at gmx.de wrote:
> Hi,
> this is rather off topic, but as I can't find any useful information googling and know the nice and helpful people on this list, I try asking :-)
> (Also, it's peripherally related as it's about calculating velocity from a smartphone's acceleration data using moby :-;)
> To calculate velocity from acceleration I'd like to use Euler integration (at least this is what people normally seem to do), but I have no idea what to do about the initial velocity.
> 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.

I am afraid you will have to assume 0 when tha application starts. There 
is no way you can determine absolute speed using an accelerometer alone.

OTOH you could add a "calibrate" button to the interface and request the 
user to press it while standing still.
You will get funny results if someone calibrates inside a moving vehicle 
which sometimes stops (like a bus). ;]

Jakub Piotr Cłapa

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