1. Key words: retrogressive landslide, clay shale, residual strength, movement rates, geological age, inclinometer.

2. Then you use a compass and an inclinometer to measure the direction the cave is headed and measure the slope of the floor and the ceilings.

3. [Bluetooth Accelerometer+Inclinometer] BWT901CL MPU9250 High-Precision 9-Axis Gyroscope+Angle(XY 0.05° Accuracy)+Magnetometer with Kalman Filter, 200Hz High-Stability 3-axis IMU Sensor for Arduino 3.8 out of 5 stars 30

4. The apparatus uses a two-axis inclinometer that is attached in the region of the patient's upper body to measure the absolute angular elevation of the patient's upper body, which is then transmitted to a display or other output device.