Well just read the first sentence: "The difference between gyroscope and accelerometer is that the former can sense rotation, the latter cannot" Quite simple if you stick with that.
Trouble is it's not true. Jet Car Stunts, for instance, uses the accelerometer to let you turn the car by turning your device like a steering wheel rather than tilting it.
The gyroscope has an additional axis that can sense movement of rotation, not just tilt. Don't argue.
Maybe turning the device like a steering wheel is using the tilt function because that's how you control all the other racing games with the accelerometer besides the newly updated real racing. Kgtfo. Rotating means not moving your iPod on the x-axis, but only on the y-axis. If that's not comprehendable, there's a big problem here.
Accelerometer: Can detect ACCELERATION along x, y and z axis Gyroscope: Can detect ROTATION around the x, y, z axis Simple
Knowing that any game ask you define a start initial position the accelerometer seems a lot more powerful to detect any movement you are giving to your device. If the accelerometer detect acceleration for all axis when you rotate the device around you involve an acceleration on at least 2 axis. And if that don't change you know the rotation continue until you stop the rotation then there's again an acceleration change on at least 2 axis. Another point, take care only rotate the iPad device itself and at some point it seems detect an angle involving the screen position change. So even for the device itself rotation seems detected by the accelerometer. I made another experience with the iPad, I made a hardware shutdown in hope of stopping any function including accelerometer functions. Then upside down the iPad and then start it trying not moving, I was doing small movements but nothing allowing identify the upside down and at restart the screen position has changed and detected the iPad position change. Ok one possibility is that the hardware shutdown never stop the accelerometer functions. I suppose what I write above is wrong otherwise I wonder the use of the gyroscope. Perhaps more precision or to not have to ask the player a start initial position in some circumstances.
Think of it this way (hopefully I have this correct): The accelerometer can detect where (and with what intensity) the force of gravity is coming from (this also includes acceleration). If you turn your iDevice from portrait to landscape, gravity changes from pulling down through the dock connector to pulling down through the side of the phone. However, if you were to slowly spin in a circle while holding your iDevice the same way, gravity is still pulling the same way at all times. This is where the gyroscope comes in; it can detect rotation.
Mmmm but if you rotate there's in fact an acceleration too at the beginning of the movement, at least if it's really a detection on the 3 axes. But it's clear that no iPad game exploit such rotation as if it's impossible. For me there's something still not clear with the impossibility to detect such movement and the ability to detect gravity and acceleration on the 3 axes. But with a slow rotation there will be a very slow acceleration on at least 2 axes at the start of the movement so it's perhaps a problem of sensitivity or there's another point?
The gyroscope can sense 3 different axises of motion, the accelerometer does only 2. For example, you could move your iPhone 4 forward and it can notice that unlike the past generations.
That's not correct. Accelerometer can detect ACCELERATION in all 3 axis. And gyroscope detects ROTATION around the 3 axis. It's similar to the wiimote (accelerometer) and motion plus attachment (gyro). You CAN get single axis gyro (ps3 controllers have 3 axis accelerometer and single axis gyro), but the iDevices have a 3 axis accelerometer and a 3 axis gyro.
An accelerometer measures acceleration. A 3-axis accelerometer will tell you the orientation of a stationary platform relative to earth's surface, once that platform starts moving, however, things get more complicated. If the platform is in free-fall, it will show zero acceleration. If it is accelerating in a particular direction, that acceleration will simply be added to whatever acceleration is being provided by gravity, and you will not be able to distinguish. A 3-axis accelerometer in an aircraft in a properly coordinated turn with a 60 degree angle of bank, for instance, will show 2 G "vertical" acceleration in the aircraft, despite the fact that the aircraft is tilted 60 degrees relative to the horizon. So, accelerometers alone can't be used to keep in an aircraft in a particular orientation. A gyro measures rate of rotation around a particular axis. If a gyro is used to measure the rate of rotation around the aircraft roll axis, it will measure a non-zero value as long as the aircraft is rolling, but measure zero if the roll stops. So, a roll gyro in an aircraft in a coordinated turn with a 60 degree bank will be measure a rate of zero, same as an aircraft flying straight and level. You can approximate the current roll angle by integrating the roll rate over time, but you can't do so without some error creeping in. Just to make life more interesting, gyros drift with time, so additional error will accumulate over a period of minutes or even seconds, and eventually, you'll have a totally inaccurate idea of your current roll angle relative to the horizon. So, gyros alone can't be used to keep in an aircraft in a particular orientation. hope this helps.
