Sevenson understands the importance of precision when executing environmental dredging, excavation, and ISS projects; the necessity to minimize over dredging or over excavation; and the need for robust, reliable systems when equipment is in operation. Sevenson utilizes dredge positioning systems developed by Trimble Marine Construction and Hypack.
The systems use a combination of inclinometers, software and dual RTK GNSS antennas for accurately positioning the dredge bucket, cutter head, or auger. A Trimble base station is set up on site and checked in regularly to provide accurate GPS corrections to GPS equipment and site rovers. The pre-dredging surface and target dredging prism are programmed into the system along with relevant linework.
The operator can simultaneously view a plan and profile of the dredge cut on the computer screen. Data from the system will be utilized daily to assess coverage, quantities, and completion. In addition to the XYZ data collected by the system, Sevenson will also use survey data to QA work performed. Sevenson invested over $3M in hardware, software, programming, and PLC controls in recent years. We run the Trimble Marine Construction dredging system and Dredgepack system on over 55 pieces of equipment across the country, 24 base stations, and 23 rovers with the ability to add more. In addition, Sevenson has five full-time GPS technicians and extensive experience implementing, creating, or modifying design files for our GPS systems.
Hydraulic Dredging: Utilizes two RTK GNSS antennas in conjunction with a base station to accurately track the dredge trunnion pin position even in rapidly changing tidal environments. Inclinometers and encoders are then used depending on dredge type to translate the position tracking to the cutter head. Sevenson has been successful with the approach with various size and style dredges with project tolerances as tight as 2-in.
Mechanical Dredging and Excavation: Sevenson is experienced in multiple environments utilizing various machines for mechanical dredging. Mechanical dredge systems can either utilize GPS or UTS positioning although the former is more common due to its flexibility. GPS mechanical dredging requires dual GNSS antennas and a connection to either an onsite or remote base station for real-time corrections. Sensors on the body and each segment of the machine accurately track the cutting edge or measuring point of the excavator tool. The systems are capable of tracking numerous tool types including conventional buckets, clam shell buckets, and grapples. The systems are extremely rugged and designed for aquatic and terrestrial environments. They provide the operators with critical real time information, surface tracking, and various views to complete complex design surfaces. UTS dredge systems operate with the same functionality, but positioning is provided by a robotic total station. This setup is useful for completing excavation areas with limited or no sky coverage. A prism is mounted off center on the machine and tracked by the total station. When the machine rotates, the station can determine heading due to the mounting position of the prism.
ISS: Positioning for ISS rigs and excavators performing bucket mixing is accomplished similarly to the aforementioned GPS systems. For the drill rigs, two GNSS antennas are mounted on the mast of the rig and coupled with angle sensors to accurately align the auger at each mixing location. The position is accurate real-time with corrections from an onsite base station. The operator is able observe the alignment and ensure the proper depths of mixing are achieved. The ISS excavators operate using the same system as the dredging and excavation excavators with some additional protection added.
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