This 4 in 1 multi-Sensor module has Gyroscope, Accelerometer, Magnetic Compass and Pressure sensor all on single PCB with I2C and SPI communication interface. This 10-DOF GY-91 sensor module is more compact than GY-80 module. The module uses combination of Single chip MPU-9250 with built-in 3 axis Gyro, 3axis Accelerometer, digital Compass and BMP280 improved barometric pressure sensor.
The MPU-9250 is the company’s second generation 9-axis MotionTracking device for smartphones, tablets, wearable sensors, and other consumer markets. The MPU-9250, delivered in a 3x3x1mm QFN package, is the world’s smallest 9-axis MotionTracking device and incorporates the latest InvenSense design innovations, enabling dramatically reduced chip size and power consumption, while at the same time improving performance and cost.
Bosch BMP280 is a better version of popular BMP180. It's 63% smaller than BMP180. With lower noise, lower current consumption, higher resolution, additional SPI interface. New filter modes, etc.
Improvements include supporting the accelerometer low power mode with as little as 6.4µA of and it provides improved compass data resolution of 16-bits (0.15 µT per LSB). The full scale measurement range of ±4800µT helps alleviate compass placement challenges on complex pcb’s
Documents and Downloads
What is Degrees of Freedom (DOF), see here