Ship geometry / Offset survey / Dimension control
As part of the quality assurance of the hydrographic process the position of the sensors must be recorded in relation to the ship’s geometry. The determination of the ship’s geometry is carried out to get the relative relationship between the various sensors and antennas that are used in the hydrographic data acquisition software.
The accuracy of the geometry is not allowed to significantly influence the total hydrografical process.
Not only the ships geometry is determined but also the angle of the multibeam and the position of the phase centres of positioning sensors are calculated.
Beside the determination of the acoustic sensors, the corrections of the heading (heading) and the motion sensors (roll, pitch) is also measured and calculated
It is a standard procedure of the survey to fix the geometric system on board the vessel by means of benchmarks. This makes it possible to determine new sensors, mounted above the waterline at a later stage and survey the position and direction without the need for the vessel either to be lifted or to dock. The position of the motion sensor (phase center, MRU / Octans) is also determined. However, the accessibility of these sensors will strongly affect the accuracy of this position.
High accuracy and reliability are assured by settling all observations with the least squares solution method. All validated data will be presented together with the calibration values in a clear ships calibration report.