This course delivers insight into the key principles of motion, attitude, timing and reference systems as applied in hydrographic survey operations. Participants will explore how motion and direction sensors function, including motion reference units, inertial navigation systems, gyro compasses and Doppler logs, as well as the importance of time synchronisation, latency, update frequency and survey system timing. A basic introduction to geodetic reference systems is also included to help understand the constraints and possibilities when calculating position and direction in survey techniques.