Neo1973 Update!

Tim Newsom cephdon at
Tue Jun 5 05:20:36 CEST 2007

If your tracking movement with 2 3D accelerometers... What would another 
one provide.
As far as I can tell (I am not an expert...)
Tracking all 6 vectors will tell you absolute movement in space.  I.e, 
when 2 vectors point in the same direction with the same magnitude at 
approximately the same acceleration as gravity.. Its probably laying or 
positioned flat on that side.
If they vary and you have 4 vectors.. (Necessary when its tilted beyond 
the error amount...) You can figure out its orientation and angle.  If 
its spinning around its center (and assuming that the accelerometers are 
on opposite ends...) Then at least 4 vectors will point away from each 
other at approximately the same magnitude as its opposite but matched 
vector. (The other 2 may point down or up depending on if its spun flat 
or thrown or dropped. But they should be the same for a flat spin..)  
All vectors should be able to tell you the moment of movement and the 
phones basic translation in space... Especially if you keep track of the 
last known states... Right?

I mean  if we know the rest orientation and then suddenly get pointed at 
something it would seem like the 3d vectors will show a specific values 
and directions for the 2 ends of the phone depending on the center of 
the arc or movement that acted on the phone.

I would say that we can get yaw, pitch and roll just fine.. But again, I 
am no expert.


On Mon, 4 Jun 2007 18:38, kkr wrote:
> If I well understand, three accelerometers are necessary to fully 
> define
> all phone's movements. Isn't it?
> So, what's the reason to have only two, and not three 3D 
> accelerometers?
> - the cost?... 3 $US (But I don't know if it's a 2D or 3D chip).
> - the lack of free space?
> - ...
> Is-it a 3D or a 2D chip?
> Regards,

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