What is heave?
Heave is the vertical translation of the vessel under wave action. If the hull rises 40 cm while a sounder samples the bottom, the instantaneous transducer-to-bottom distance changes by the same amount even when the true seabed is flat.
Roll, pitch and lever arms
A transducer away from the rotation centre also moves vertically as the vessel rolls and pitches. The geometry between the motion reference and transducer therefore matters.
Conditions for useful compensation
Fast measurement
The motion estimator must follow the vessel dynamics.
Coherent timing
Depth and attitude must refer to the same instant.
Known geometry
Sensor positions and axes must be documented.
Suitable filtering
The estimator must separate oscillatory motion from slow reference changes.
The role of Hannon GeoX
GeoX calculates roll, pitch and heave from GNSS/inertial fusion and publishes these quantities to compatible consumers. Final survey quality also depends on the sonar, timing, installation geometry and processing software.