imu coordinate frame

[Lishen1]

in readme written that imu in NED coordinate frame (z axis towards down) but in imu data file sign of z axis acceleration is negative (while expected positive )

[thlsealight]

The IMU used is in the front-right-down (FRD) frame, while is a local frame. In contrast, the NED frame is a global frame. Besides, please note that the sign of the z-axis acceleration should be negative rather than positive.