Accelerometer wiki page erroneous axes ?

Paul Fertser fercerpav at
Wed Apr 8 15:02:55 CEST 2009

Paul Fertser <fercerpav at> writes:
?> Michael Tansella <michael-tansella at> writes:
>>> So, the fact that when idle the accelerometers report a positive Z value
>>> implies that the Z axe is actually upward.
>>> Agree ?
>> Yes I think that's right. If you hold the Freerunner that any arrow of an axis 
>> points to the earth middlepoint then the sown value must be
>> negative.
> I beg to disagree. If you are talking about acceleration of the sensor
> itself then you'll see that: 1. it's not actually accelerating if you
> attach a reference frame to the Earth (the freerunner is laying
> still). 2. The gravitational force applied to the sensor is directed
> to the center of the Earth, so the reported "acceleration" should be
> positive too.

Thinking about it a bit more, i now understand that if you insist on
talking about accelerations, the Z axis should point upwards.

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