Safe and Accurate Installation of Structures Underwater

Underwater positioning system using the RTK-GNSS underwater positioning device, for better accuracy and safety

Here we introduce an underwater positioning system for the laying of covering blocks and asphalt mats for breakwater wave dissipating block installation work.
In this case, a high-precision transponder and RTK-GNSS were used in the development and employment of a system for displaying the positions of the components being installed and the divers, in both plane and cross-sectional views.

Installation on Crane Barge

A transceiver, motion sensor, RTK-GNSS (mobile station) and GNSS compass were attached to a pole.

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For test measurements, the pole was fitted to the port side of the work ship.
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GNSS Base Station Installation

A GNSS base station was installed on the breakwater.

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Test measurement

The transponder was bottomed at the test measurement position. In this example the transponder was set at a depth of about 10 meters.

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Installation operation measurement

For the laying of asphalt mats, measurement is performed with an underwater positioning system. The devices and computer used for measurement are all placed in a booth on the crane barge, and during measurement the computer screen is made visible to the crane operator as well, via LAN.

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Transponders are fitted to both ends of the asphalt mat lifting apparatus, as well as to the divers.

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The position where the mats are being laid is displayed in real time on the measurement screen. The blue area on the screen is the target position for laying the mats, the purple frame is the current position of the lifting apparatus, while “1” and “2” indicate the positions of the divers.

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For details, refer to “USBL Type Underwater Position Measurement”

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