# 4.4 Position and Velocity data

Positional and velocity data are published on the /nav/pose and /nav/twist topics.

In the /nav/pose positions messages, ‘x’ is the latitude coordinate, ‘y’ is the longitude coordinate and ‘z’ is the heading of the vessel in degrees (measured clockwise with 0 degrees facing north). The orientation messages contain the vessel’s rotation in quaternions.

The /nav/twist linear messages contain the vessel’s linear velocities in the body-fixed frame, measured in meters per second. The angular messages contain the vessel’s angular velocity, measured in radians per second.


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