Abstract: An underwater EM measurement system, which is substantially smaller, much simpler to use, and more robust than prior systems, is formed as a sensor package integrated into a single pressure vessel includes two magnetic sensors including induction coils disposed substantially horizontally so as to measure fields in orthogonal directions. The package also includes two electric field sensors including electric potential antennas adapted to couple to a water potential via a capacitive electrode having a conducting material and an electrically insulative layer formed of an insulating material. The capacitive electrode has a capacitance to the medium of greater than 1 mF. Preferably, the insulating material is a metal oxide.

Abstract: The present invention discloses a tagging and identification device and system for tracking and monitoring sea vessels as they enter sea ports, estuaries and/or other channels. The tagging device of the present invention comprises a receiver, for receiving an underwater electromagnetic signal transmitted by an underwater beacon. An acoustic transmitter is provided for transmitting an identification signal to an acoustic receiver deployed nearby. The acoustic identification signal is transmitted after an electromagnetic trigger signal is received from the underwater beacon. The tagging and device may further comprise a memory device which can store data relating to position and time of the see vessel to which it is attached. The tagging and identification device of the present invention is covert, compact and is capable of extended active deployment without replenishment of batteries etc.

Abstract: The present invention discloses a tagging and identification device and system for tracking and monitoring sea vessels as they enter sea ports, estuaries and/or other channels. The tagging device of the present invention comprises a receiver, for receiving an underwater electromagnetic signal transmitted by an underwater beacon. An acoustic transmitter is provided for transmitting an identification signal to an acoustic receiver deployed nearby. The acoustic identification signal is transmitted after an electromagnetic trigger signal is received from the underwater beacon. The tagging and device may further comprise a memory device which can store data relating to position and time of the see vessel to which it is attached. The tagging and identification device of the present invention is covert, compact and is capable of extended active deployment without replenishment of batteries etc.

Abstract: An underwater EM measurement system, which is substantially smaller, much simpler to use, and more robust than prior systems, is formed as a sensor package integrated into a single pressure vessel includes two magnetic sensors including induction coils disposed substantially horizontally so as to measure fields in orthogonal directions. The package also includes two electric field sensors including electric potential antennas adapted to couple to a water potential via a capacitive electrode having a conducting material and an electrically insulative layer formed of an insulating material. The capacitive electrode has a capacitance to the medium of greater than 1 mF. Preferably, the insulating material is a metal oxide.