A method and apparatus for monitoring a structure using an optical fiber based distributed acoustic sensor (DAS) extending along the length of the structure. The DAS is able to resolve a separate acoustic signal with a spatial resolution of 1 m along the length of the fibre, and hence is able to operate with an acoustic positioning system to determine the position of the riser with the same spatial resolution. In addition, the fiber can at the same time also detect much lower frequency mechanical vibrations in the riser, for example such as resonant mode vibrations induced by movement in the surrounding medium. By using vibration detection in combination with acoustic positioning then overall structure shape monitoring can be undertaken, which is useful for vortex induced vibration (VIV) visualisation, fatigue analysis, and a variety of other advanced purposes. The structure may be a sub-sea riser.

Disclosed are methods and systems for determining distance between two or more mobile devices utilizing a sound emitted from each device such as a chirp. Each device may determine or receive an indication of a time reference for each instance the device emits or detects a chirp. Utilizing the time reference data, the distance between the two or more devices may be determined assuming the sound travels at a constant speed of 340.29 m/s. Techniques for disambiguating orientation of the devices relative to one another rare also disclosed.

Disclosed are methods and systems for determining distance between two or more mobile devices utilizing a sound emitted from each device such as a chirp. Each device may determine or receive an indication of a time reference for each instance the device emits or detects a chirp. Utilizing the time reference data, the distance between the two or more devices may be determined assuming the sound travels at a constant speed of 340.29 m/s. Techniques for disambiguating orientation of the devices relative to one another rare also disclosed.

A positioning system has an initiator device configured for emitting a high-speed wireless signal, at least one reference device configured for receiving the high-speed wireless signal and emitting a low-speed wireless signal after receiving the high-speed wireless signal, at least one target device each having one or more components for receiving the low-speed wireless signals, and at least one engine configured for determining the position of each of the at-least-one target device by calculating the distance between the target device and each of the at-least-one reference device based on at least the times-of-arrival of the low-speed wireless signals, each time-of-arrival being the time that the corresponding low-speed wireless signal being received by the target device, and determining the position of the target device based on the calculated distances.

A method and apparatus for locating a target in a venue is described. A backend controller activates transmitters in a venue to send burst signals using a double symmetry configuration formed of a plurality of separate transmitter groups. The backend controller activates the transmitters into a second, different configuration for bursting. The resulting location signal information from each configuration is obtained by the backend controller, which then more accurately determines the location of the target in the venue.

A method and apparatus for locating a target in a venue is described. A backend controller activates transmitters in a venue to send burst signals using a double symmetry configuration formed of a plurality of separate transmitter groups. The backend controller activates the transmitters into a second, different configuration for bursting. The resulting location signal information from each configuration is obtained by the backend controller, which then more accurately determines the location of the target in the venue.

A positioning method using music pieces continuously provides positioning service. At each signature burst (i.e., a highly unique short musical segment suitable for positioning), sounds of a music piece are used for positioning. Between signature bursts, dead reckoning (DR) is used.

Systems and methods for location estimation and tracking for passive RFID and wireless sensor networks in accordance with embodiments of the invention are disclosed. In one embodiment, a process for obtaining location information using an RFID reader system includes transmitting a combined interrogation and ranging signal from a plurality of antennas, where the ranging signal is a pseudorandom signal, receiving a backscattered return signal from an RFID tag at one or more receive antennas, extracting an information signal from the return signal and decoding the information signal to obtain RFID tag data, extracting a received ranging signal from the return signal, and estimating a range to the RFID tag based upon correlation between the ranging signal and the received ranging signal.

Systems and methods for location estimation and tracking for passive RFID and wireless sensor networks in accordance with embodiments of the invention are disclosed. In one embodiment, a process for obtaining location information using an RFID reader system includes transmitting a combined interrogation and ranging signal from a plurality of antennas, where the ranging signal is a pseudorandom signal, receiving a backscattered return signal from an RFID tag at one or more receive antennas, extracting an information signal from the return signal and decoding the information signal to obtain RFID tag data, extracting a received ranging signal from the return signal, and estimating a range to the RFID tag based upon correlation between the ranging signal and the received ranging signal.

A laser marking method for an electronic device with a projector and a projection screen includes first and second microwaves being received by microwave receivers on corners or elsewhere of the projection screen. First and second microwave transmitters in a laser pen transmit the microwaves. Time intervals between transmissions and receptions of the microwaves are acquired. Distances between each of the microwave receivers and each of first and second microwave transmitters are calculated, to establish a three-dimensional rectangular coordinate system. Coordinate value of a point on the screen struck by laser beam (drop point) from the pen is calculated. The method allows for marking the drop point on the screen and also for marking a series of drop points with a line when the laser beam moves across the screen.