Author : Cao Year : 2022
- Fusion of VIO with GNSS pseudo-range and doppler shift measurements in a factor graph
- a quantity tought to be estimated is the 4 Dof transform between the local VIN frame and the global GNSS frame
- tight fusion
- GNSS - VI fusion with EKF : UAV position and attitude estimation using IMU, GNSS and camera + A robust and modular multi-sensor fusion approach applied to MAV navigation
- ECEF = earth centred, earth fixed
$xy$ coincide with earth equatorial plane with$z$ pointing to the north and$x$ to the prime meridian - ENU = semi global frame that is East, North and Up (gravity aligned)
- ECI = earth centred inertial frame: inertial coordinate system with center of mass of earth as origin and fixed wrt the stars (ie does not rotate with earth)
- Estimates a sliding window of poses and inverse depth, the yaw offset between local world frame and ENU frame, receiver clock bias and receiver drifting rate
- "pseudo" range cause contains various errors
- Single Point Positionning (SPP) algo to perform trilateration in the ECI frame => four satellites needed
- INIT :
- classic Sfm for VI init
- coarse anchor pose with SPP
- yaw alignment with doppler meas
- anchor refinement that imposes a clock constraint
- Uses Doppler to find yaw: have a velocity estimate to align with VIO one
- Yaw offset cannot be estimated with low velocity
- loop closure disabled for experiments