Reference Frame Surveys
Any Hydrographic vessel will need to defined its pitch, roll and heading from true North. In hydrographic surveying, determination of these parameters is essential for the correction of sub-sea echo sounder measurements.
Above the waterline, the vessel will have DGPS (Dynamic Global Positioning System) antennae and either an IMU (Inertial Measurement Unit) or MRU (Motion Reference Unit).
Below the waterline, the vessel may have multi-beam or single beam echo sounders.
To function correctly all components have to be surveyed and co-ordinated in a common co-ordinate system related to the vessel centreline and waterline. The pitch, yaw and roll of each relevant component also has to be determined.
The greater the precision of the surveyed pitch, roll and yaw, the more precise the final sub-sea survey data will be once their correction has been applied.