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24 st / February 2017 www.sea-technology.com To meet these monitoring requirements, develogic de- livered a turnkey monitoring system measuring sediment load and ocean current at several levels, as well as potential movement and vibration of the submarine hull due to the impact of the materials that make up the counterfill, together with deployment and operation support services. The extensive system included 10 CSL.1000 seafloor landers, one SB.600 telemetry gateway buoy, an MI.Sat II backup buoy, as well as the entire data storage, processing and visualization solution. Real-time data transmission from the seafloor landers was conducted via inductive and acous- tic telemetry. Violation of predefined thresholds for sediment load in the ocean current outside of the operation area or detected wreck motion was to cause alert notifications and subsequently interrupt work activities. Measurement Platforms The subsea part of the monitoring system was de- signed around develogic CSL.1000 compact seafloor landers equipped with inductive and acoustic telemetry integrated into a network together with the surface buoy. These landers are a fully integrated instrument platform with all subsystems necessary for deployment, opera- tion, data transmission and recovery. The key lander systems—data logger and processor, release actuator, satellite beacon, smart power supply, acoustic and in- ductive modems—are all linked to the communication network with individual addresses. This provides maxi- mum flexibility in system configuration and operation. It is possible, for example, to switch data transmission on the fly from the acoustic to the inductive telemetry, reroute data in case of component dropout or diagnose and reconfigure all systems via the available commu- nication interfaces. This feature is especially useful by enabling the possibility of remote support from the manufacturer via Iridium satellite transponder integrated into the GPS/Iridium beacon. This platform provides exten- sive support for sensor integra- tion: Up to eight sensors can be interfaced in the basic version via RS232/422/485 and Ether- net. The power supply voltage to the attached sensors is program- mable. High energy capacity of up to 4,400 Wh paired with the low power consumption of the core system allows for extensive deployments up to several years. As part of the U-864 coun- terfill monitoring project, acous- tic Doppler current profilers for monitoring ocean currents and turbidity sensors were installed on a short mooring at 1.5 and 10 m above the seafloor to measure sediment load at these levels. Multiple inclinometers and shock sensors were attached to the wreck hull. The landers relayed data via inductive and acoustic (Top) CSL.1000 seafloor lander prior to linking to the inductive network underwater. (Middle) Laying of the steel wire inductive communication cable by ROV, involving cable reel with con- tactless connection spike. (Bottom) Web portal with visualization of turbidity, inclinometer and ocean current data.