Chris Emerson wrote:
>>> I thought that at first, but you can have other forces and still
>>> have a
>>> 1g vector.  As an extreme example, add a 2g vector in the opposite
>>> direction.
>>
>> That example isn't included in my solution space.
>> I said above or below 1g :-).
>
> True, when it's != 1g you know there's some acceleration, but when it's
> 1g there might still be some.

This is because you are treating a vector as a scalar.  The 3 axis system
works in theory if you can subtract the gravity accelleration vector.
Unfortunately while its magnitude is easy (1g), it's direction is not so
easy to know without essentially doing an inertial navigation solution.

While this is an interesting theoretical discussion, I don't think something
like this is practical for a car to determine braking.  I've also got
serious concerns about the desirability of blinking a brake light in the
first place.


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