estimator module group is implemented in
agilib/src/estimator. There are different types of estimator, depending on the information they use:
ekf: An EKF propagated with a constant acceleration model and updated with 6-DoF pose and IMU measurements.
ekf_imu: An EKF propagated with IMU measurements and updated with 6-DoF pose measurements.
feedthrough: The estimation is provided completely from an external estimator.
mock_vio: A mock estimator that corrupts a ground-truth estimates with noise and bias to simulate real-world properties.