Abrégé

A method of acquiring field data with a plurality of underwater nodes. The nodes are deployed and each acquires a position estimate which is indicative of its position, typically on the seabed. Each node transmits its position estimate and a time estimate based on its own clock to a plurality of other ones of the nodes. Each node receives and stores position and time estimates from other ones of the nodes. Each node determines a range between the node and its nearest neighbours from which it has received position estimates, and then improves its own position estimate based on the position estimates and ranges of its nearest neighbours, for instance by trilateration. Each node also receives time estimates which have been transmitted from other ones of the nodes and synchronises its own clock based on those other time estimates. Field data is acquired with each of the nodes and stored along with the improved position estimates and time estimates.

Classes IPC  ?

• G01V 1/38 - SéismologieProspection ou détection sismique ou acoustique spécialement adaptées aux zones recouvertes d'eau
• G01S 5/30 - Détermination de distances absolues à partir de plusieurs points espacés d'emplacement connu

Abrégé

A method of determining the position of an underwater node. The positions of three or more transmitters are determined. Each transmitter transmits at least four pulses, wherein a time difference between each pulse and a previous one of the pulses is proportional to a respective co-ordinate of the position of the transmitter. The pulses are received at the underwater node and decoded by measuring the delays between them, thereby determining the co-ordinates of the transmitters. The range of each transmitter relative to the underwater node is also determined. Finally the position of the underwater node is determined in accordance with the co-ordinates and ranges. Any errors in the measurements of the delays between the pulses only translate into small errors in the determined position because of the proportionality between the delays and the coordinates. Therefore if there is a gradual decrease of signal-to-noise ratio then the accuracy of the position estimate also degrades gradually. Also, the use of pulse position modulation provides a low computation overhead in decoding and encoding.

Classes IPC  ?

• G01S 5/30 - Détermination de distances absolues à partir de plusieurs points espacés d'emplacement connu

Abrégé

A method of communicating with an underwater vehicle comprising a propulsion system for propelling the vehicle through the water. A series of data sets are encoded and transmitted to the underwater vehicle in a series of signal bursts, and decoded at the underwater vehicle. The propulsion system is operated in a series of thrust pulses separated by drift periods such that the propulsion system operates at a relatively high rate during the thrust pulses and at a relatively low (or zero) rate during the drift periods. The drift periods are timed such that each signal burst arrives at the underwater vehicle during a drift period and not during a thrust pulse. The method may be performed with a single vehicle or a plurality of underwater vehicles. The encoded data signals are broadcast simultaneously to the underwater vehicles in the series of signal bursts.

Classes IPC  ?

• B63G 8/00 - Navires submersibles, p. ex. sous-marins
• H04B 11/00 - Systèmes de transmission utilisant des ondes ultrasonores, sonores ou infrasonores
• G01S 5/30 - Détermination de distances absolues à partir de plusieurs points espacés d'emplacement connu
• H04L 25/49 - Circuits d'émissionCircuits de réception à conversion de code au transmetteurCircuits d'émissionCircuits de réception à pré-distorsionCircuits d'émissionCircuits de réception à insertion d'intervalles morts pour obtenir un spectre de fréquence désiréCircuits d'émissionCircuits de réception à au moins trois niveaux d'amplitude

Abrégé

An annular vehicle having a body which defines a body axis and appears substantially annular when viewed along the body axis. The interior of the annulus defines a duct which is open at both ends. The vehicle includes an electric field (EF) coupled dipole antenna arrangement for electro-magnetic communications, which includes at least one dipole antenna. The vehicle is used as a node in an underwater communications system for communicating with other node(s) using their EF coupled dipole antenna arrangements. The electric field coupled dipole antenna arrangement can provide communications with lower latency than systems employing acoustic communications. The annular body provides good separation for electrodes of the EF coupled dipole antenna arrangement disposed around the body.

Classes IPC  ?

• H01Q 1/34 - Adaptation pour l'utilisation dans ou sur les navires, les sous-marins, les bouées ou les torpilles
• B63G 8/00 - Navires submersibles, p. ex. sous-marins
• B63H 5/00 - Aménagements à bord des navires des éléments propulsifs agissant directement sur l'eau
• H01Q 21/26 - Antennes tourniquet ou similaires comportant des dispositions de trois éléments ou plus allongés disposés radialement et symétriquement dans un plan horizontal par rapport à un centre commun
• H01Q 21/28 - Combinaisons d'unités ou systèmes d'antennes sensiblement indépendants et n’interagissant pas entre eux