Real-time elevation and penetration-rate monitoring with Zupt's iRTS
During monopile installation, positioning equipment around the hammer can lose satellite visibility as the pile approaches its final elevation.
Cranes, slings, spreader bars, and other deck equipment can obstruct GNSS signals. If installation is taking place from a floating vessel, the survey system also needs to account for vessel motion.
The installation team still needs to measure where the pile is, how quickly it is descending, and how close it is to its intended elevation.
Separating the Positioning Reference From the Hammer
A GNSS receiver mounted on the hammer or gripper depends on satellite visibility at that location. Zupt's Integrated Robotic Total Station (iRTS) uses a different arrangement.
Two robotic total stations are mounted high on the vessel, where GNSS visibility is clearer. They automatically track shock-mounted prisms on the hammer or gripper.
RTK GNSS provides the absolute positioning reference. The total stations measure the tracked prisms relative to that reference, while a navigation-grade inertial measurement unit (IMU) accounts for vessel motion.
The arrangement allows iRTS to follow the target's position and elevation without depending on satellite reception at the hammer itself. Optical sightlines between the total stations and prisms are still required.
Measuring Descent as It Happens
Knowing the final elevation is only part of the requirement. During installation, operators also need to follow the pile's rate of descent.
iRTS provides real-time position, elevation, and penetration-rate data, with more than five updates per second while tracking a prism. These measurements help the installation team assess progress toward the target elevation and monitor for pile run, when a
pile descends rapidly and unexpectedly.
The system supports both fixed and floating vessels. On a floating vessel, the integrated IMU allows the measurements to account for movement of the survey equipment as the vessel moves.
The integration also supports operation through short-term GNSS outages. Outages lasting more than 10 seconds require RTK recovery.
Offshore Performance
Operating from a dynamically positioned installation vessel, iRTS tracked monopile descent with significant offsets between the vessel-mounted sensors and the hammer.
These deployment results demonstrate the system's ability to track pile descent from a moving vessel and provide elevation measurements that can be checked against the final as-found position.
Applying the System Offshore
The vessel layout determines where the total stations can be installed and how they maintain sight of the prisms throughout the required tracking range.
Mounting positions therefore need to provide both suitable GNSS visibility and optical access to the hammer or gripper. The system can be controlled remotely from another location onboard.
With that arrangement in place, the installation team can follow pile elevation and penetration rate as work progresses, including the approach to final installation elevation.
