Calibration Procedure The process starts by laying a reference beacon on the seabed followed by the vessel sailing in a calibration pattern over and around it. Simultaneously DGPS, USBL, VRU and Gyro Compass data is logged by the integrated LUSBL system.

Data Processing Firstly, DGPS and USBL range data is processed to compute an unbiased estimate of the reference beacon position, the grid sound velocity and the antenna offsets. USBL data is then compared with predicted data from the DGPS/ reference beacon to estimate the pitch, roll and heading errors. This process is repeated until the result is optimised.

Below Left: Transponder Scatter Plot before Casius Calibration
Below Right: Transponder Scatter Plot after Casius Calibration
  

Features:-

• Pitch, Roll and Heading corrections to be entered into the USBL system
• Grid sound velocity and the antenna x, y offsets with respect to the transceiver
• Easting, Northing and Depth of the reference beacon

Advantages of CASIUS processing:

• Estimate of transponder position and sound velocity are unbiased
• Processing visibility at each stage
• Antenna offset from Transceiver is an output
• Weighted matrices account for USBL errors and bad data therefore there is no need for an operator to edit data
• Reports are simple and graphic
• Roll, Pitch and Heading corrections output exactly as they should be entered into the USBL system