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How to align Gyro USBL to the vessel frame of reference

21 June 2021

A Gyro USBL contains an Attitude Heading Reference Sensor (AHRS) and a transceiver that is pre-calibrated. The Gyro USBL tightly coupled, pre-calibrated, meaning it’s portable and can be transferred from vessel to vessel without the need for calibration as the results are stored within the Gyro USBL itself.

This means only GPS offsets are required to be entered on installation. Eliminating lever arm offsets and any deployment pole or ship flexing between a separate AHRS and transceiver.

It is therefore possible to mount the Gyro USBL in any orientation to the vessel and the USBL tracking will be accurate to less than 0.1% of slant range, straight out the box. Perfect for vessel’s of opportunity.

On a ship with its own permanent heading device, it is best practice to align the transceiver in line with the rest of the vessel. This may not be possible to do physically, but you can use the Attitude/Heading Calibration option in Ranger 2 software.  You can find this option in the main menu under “Tools>Advanced”, use the ship’s sensors set as a reference point to estimate the alignment of the Gyro USBL to the ship.

Firstly, remember to enter the offsets for the ships gyro.

On completion, select “save to import”, results will automatically be entered in the “Ship to Lodestar” column in the offsets dialogue and your Gyro USBL will then be corrected to vessel frame.


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