Abstract: A worker transfers GPS signals to a communication system at each node of traveling using a cellular phone terminal, and the communication system specifies the position of the cellular phone terminal and notifies positional information to a management system. When the cellular phone terminal cannot receive GPS signals or is outside a range accessible to the communication system, it starts recording acceleration data using an accelerometer. When a communicable state is recovered, the cellular phone terminal sends GPS signals and the recorded acceleration data to the communication system. A management computer determines whether the position notified by the communication system is an intended node. If the notified position is not an intended node, the management computer derives the position of the intended node using the acceleration data, and predicts the travel route based on the node position.

Abstract: A worker transfers GPS signals to a communication system at each node of traveling using a cellular phone terminal, and the communication system specifies the position of the cellular phone terminal and notifies positional information to a management system. When the cellular phone terminal cannot receive GPS signals or is outside a range accessible to the communication system, it starts recording acceleration data using an accelerometer. When a communicable state is recovered, the cellular phone terminal sends GPS signals and the recorded acceleration data to the communication system. A management computer determines whether the position notified by the communication system is an intended node. If the notified position is not an intended node, the management computer derives the position of the intended node using the acceleration data, and predicts the travel route based on the node position.

Abstract: A method and apparatus for discharging overboard the excess water from the hopper of a hopper suction dredger, barge or scow for removing the air bubbles contained in the discharged water and for preventing the air bubbles from being entrained into the discharged water in order to prevent the turbidity of the water in the dredging area.