Work out imu drift estimate instantly with clear inputs, formula shown and shareable results.
Gyro bias integrates linearly with time while angle random walk grows with the square root of time, so bias dominates over long intervals. Accelerometer bias is worse still for position: it integrates twice, so error grows with the square of time — 0.02 m/s² gives 144 m after two minutes.
IMU drift
bias drift = bias x t; random walk = ARW x sqrt(t); position drift = 0.5 x accel bias x t^2
Because position error grows with time squared. Even a very good MEMS unit accumulates hundreds of metres within minutes without an external reference.
Fusion with absolute references: GNSS, wheel odometry, magnetometer heading or visual/lidar odometry, usually in a Kalman filter.