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When used together, a gyroscope and accelerometer provide a six-axis interpretation of movement through space. This is especially useful in hand-held devices such as mobile phones, because it can filter the unintended ambient movement and vibration of a user's hand, allowing for a more accurate measurement of intentional movements. It is valuable to understand the basic functions of a gyroscope and accelerometer to comprehend the manner in which these devices complement one another in combined operation.
An accelerometer, as the name implies, is used to measure sudden acceleration within a certain range of motion. In mobile phones, an accelerometer can interpret the orientation of the phone to change the display from portrait to landscape mode or interpret sudden motions such as shaking for mobile application interaction. Calculation of movement is possible through the measurement of the change in electronic signal as registered by the accelerometer. Depending on the angle of the device in relation to the ground, a microscopic amount of mass will move within the accelerometer circuit to cause this change in signal.
A gyroscope works by interpreting the shift in positioning from a set rate of rotation within the X, Y, and Z — left/right, up/down, forward/backward — axis. In consumer devices, this is accomplished through a constantly vibrating microscopic plate called a proof mass. For example, when a user tilts his phone toward the sky, the gyroscope is able to compare this movement to its ambient state and discern the pitch, roll, and yaw. The constant movement of the gyroscope means the orientation is never lost and the device is able to clearly discern its placement at all time
When a gyroscope and accelerometer are combined, it is possible to simultaneously measure acceleration and gravitational placement in the X, Y, and Z axis. This combination results in a total of six orientation measurements at all times. There are numerous advantages to having six directional measurements available to system processors, and many consumer device producers have taken note of this. By combining a gyroscope and accelerometer, it is possible to better stabilize cameras for clearer pictures, gaming applications can better interpret user motions for greater realism, and navigation applications can more accurately guide users by measuring their movements. A gyroscope and accelerometer are used together to create a more accurate measurement of overall movement and location through space by providing constant, cross-referenced measurements of spatial placement and acceleration.
@allenJo - This is a very illuminating article. I had no idea how the iPhone did its spin and tilt of its screen. It’s an amazing technology; my jaw dropped when a friend first showed me a demonstration years ago when those devices first came out.
The ability of the screen to adjust to your movements was almost surreal – like it was a mechanical device of some sort. I never understood how it worked, however. I just chalked it up to yet another breakthrough in computer technology.
Now I understand that it uses a gyroscope, the same device used to keep airlines in proper orientation. I hope that means I’ll never have an accident with my phone in hand.
My digital camcorder has an image stabilization system which, if I understand the article correctly, must use a gyroscope of some kind. It works okay, but not with lots of extreme movement.
The problem with video is that you are capturing a whole bunch of frames per second. Compensating for one frame of an image may be okay, but compensating for a whole bunch where they are all different pictures is another story altogether.
I have found that the image stabilization works best with minor camera jitter, like subtle hand held motion (the infamous “shaky cam” effect), but nothing more extreme than that.
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