Kalibr

Kalibr is a multi camera and IMU calibration toolbox. In addition to estimated intrinsic and extrinsic parameters of a camera/IMU system, it can estimate the clock difference between sensors. We can use this estimate to evaluate whether timestamps are correctly synched to the same clock. We have been able to measure less than 2ms difference between RGB cameras and IMUS using this tool.

Rovio

Rovio is a visual-inertial odometry package. While IMU and camera messages can arrive at different times, the timestamps must be recorded with respect to the same clock. If the clocks are within a couple miliseconds Rovio can still work however over 10ms the pose estimate will quickly diverge. According to experiments from ASL within 5ms general movement is fine but fast motions can still cause divergence. Within 2ms delay most motions can be tracked and there is no improvement in tracking for Rovio. We can evaluate the synching of sensors by seeing whether Rovio diverges with dynamic motions. We have been able to run Rovio with timestamp corrected cameras and IMUs

ICP

To evaluate the Realsense time delay we used ICP on the point clouds and compared the estimated pose to the VIO estimate. We found virtually zero delay indicating all sensor were synchronized together.