Which smartphone sensor measures orientation and rotation?

• A. Gyroscope
• B. Proximity sensor
• C. Accelerometer
• D. Magnetometer

Answer: (A)

Measuring rotation and how a device is oriented in space is done mainly with the gyroscope. This MEMS sensor detects angular velocity around the three axes, so when you rotate or tilt the phone, it records how fast and in which direction that rotation is happening. By integrating that rotation rate over time, the phone can track its orientation relative to its starting position. In real devices, the gyroscope is often used together with the accelerometer (which senses linear movement and gravity to help infer tilt) and sometimes a magnetometer (which detects Earth's magnetic field to help determine direction). The proximity sensor isn’t about orientation or rotation; it senses how close something is to the screen, typically to turn off the display when you hold the phone to your face. So the sensor that measures orientation and rotation is the gyroscope.