www.pabr.org This device detects Earth’s rotation on its polar axis. It can also be configured to find geographic north and measure latitude. Based on the same physics as navigation techniques for nuclear submarines, underground drilling. Main components: PlayStation Move controller, 45 RPM turntable, Linux PC with Bluetooth, 25 m electrical wire, DC power supply. By design the PlayStation Move can track motion, including rotations. Physics says that MEMS gyros must measure rotation, not with respect to the ground, but with respect to an inertial frame of reference (ie the distant stars). Therefore the PS Move senses Earth's rotation, right ? Yes, but it is optimized for rates of rotation that are suitable for gaming applications (up to about 500 RPM). This is 500 RPM. About 800000x Earth's rotation rate. The gyros have excellent dynamic range (16 bits). Yet Earth's rotation is only 1/20th of their resolution and 1/100th of RMS noise. But we can average as many samples as needed to reduce the noise, right ? No, because MEMS gyros suffer from bias drift, ie slow variations of their DC offset. And this is a good thing: if the PS Move gyros were too accurate, ITAR might classify them as missile components. This is why we can't have nice motion tracking. Now introducing the turntable. The turntable modulates the fraction of Earth's rotation that the gyro senses. Then we demodulate in software and the DC offset is removed by narrowband filtering. This technique is called