Accelerometer, Gyro, and Magnetometer

问题:

I'm new to Core Motion and I'm very confused. Can somebody please explain what these inputs measure and how they can be useful in simple terms?

回答1:

Accelerometers measure movement relative to gravity, by virtue of "feeling" the force of movement applied to the device. Force of movement can be described as the rate of acceleration and deceleration of the device, hence the name of this sensor.

Gyroscopes measure changes in rotation by virtue of a suspended element reporting its rotation relative to the device. As the device rotates, this suspended element doesn't rotate, so there's a report coming from it that tells you how far the phone's rotated.

Magnetometers get their idea of rotational position from the north/south magnetic fields that compasses use to know where they are relative to the poles. This data is used (primarily) to help the Gyroscope, because these things suffer from float and inertia.

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Combined, the information from these sensors, when filtered well (which Apple does for you with CoreMotion) give you all the movement of a phone.

So you can know if the user is swinging the phone around like a table tennis bat, or steering like a Wii Remote Mario style game controller, or simply walking.