Methods and systems are disclosed for determining pose information for at least one of a transmitter and receiver, both of which comprise ultrasonic transducers. A relative position is determined between the transmitter and the receiver and an orientation for at least is also determined. After obtaining field of view data for at least one of the transmitter and receiver, a field of view between them is determined, based at least in part on the field of view data, the determined relative position and the determined orientation. The pose information is then determined by weighting measurements of an ultrasonic signal emitted by the transmitter and received by the receiver based at least in part on the determined field of view relationship.

Methods and systems are disclosed for determining pose information for at least one of a transmitter and receiver, both of which comprise ultrasonic transducers. A relative position is determined between the transmitter and the receiver and an orientation for at least is also determined. After obtaining field of view data for at least one of the transmitter and receiver, a field of view between them is determined, based at least in part on the field of view data, the determined relative position and the determined orientation. The pose information is then determined by weighting measurements of an ultrasonic signal emitted by the transmitter and received by the receiver based at least in part on the determined field of view relationship.

The present disclosure relates to an acoustic position determination system that includes a mobile communication device and at least one base transmitter unit. The mobile communication device is configured to identify a peak in the received signal, and to de-convolve the signal with all codes that are relevant to the area in which the signal is received. A joint likelihood that a potential code is correct is formed by determining a likelihood based on a signal parameter such as signal-to-noise ratio and a likelihood based on time-of arrival information.

The present disclosure relates to an acoustic position determination system that includes a mobile communication device and at least one base transmitter unit. The mobile communication device is configured to identify a peak in the received signal, and to de-convolve the signal with all codes that are relevant to the area in which the signal is received. A joint likelihood that a potential code is correct is formed by determining a likelihood based on a signal parameter such as signal-to-noise ratio and a likelihood based on time-of arrival information.

An apparatus (7) for down-converting a sampled signal comprises a processing system (206) configured to apply a mixing-and-combining operation repeatedly to successive sub-sequences of N input samples, X, representative of a signal and having an initial sampling rate, M, to generate a sequence of output samples, Y, having an output rate, T, lower than the initial sampling rate M. The sub-sequences of the N input samples, X, are spaced at intervals that correspond to the output rate M. The mixing-and-combining operation generates a respective output sample Y from each sub-sequence, where Y depends on a set of products of the input samples X of the sub-sequence with respective values derived from a periodic mixing signal having a mixing frequency.

An apparatus (7) for down-converting a sampled signal comprises a processing system (206) configured to apply a mixing-and-combining operation repeatedly to successive sub-sequences of N input samples, X, representative of a signal and having an initial sampling rate, M, to generate a sequence of output samples, Y, having an output rate, T, lower than the initial sampling rate M. The sub-sequences of the N input samples, X, are spaced at intervals that correspond to the output rate M. The mixing-and-combining operation generates a respective output sample Y from each sub-sequence, where Y depends on a set of products of the input samples X of the sub-sequence with respective values derived from a periodic mixing signal having a mixing frequency.

To acquire distance information with high accuracy with a simple configuration, and perform highly reliable positioning.

A communication device includes a distance acquisition unit that acquires distance information calculated on the basis of a propagation channel characteristic, and an altitude acquisition unit that acquires altitude information.

A system is provided for determining the position of a mobile receiver unit (7) in an environment (1). The system comprises a plurality of transmitter units (2, 3, 4, 5) which transmit a respective phase-modulated transmitter-unit identifier, a mobile receiver unit (7), arranged to receive a signal from a transmitter unit (2, 3, 4, 5), and a processing subsystem (205; 9). The processing subsystem (205; 9) is configured to sample received signals to generate sampled data, wherein the identifier spans a transmitter-unit-identifier-bearing portion of the sampled data, obtain template data corresponding to the identifier, analyse the sampled data to determine a Doppler-induced phase deviation, adjust the template or the sampled data to change one or more phase shifts by an amount depending on the determined deviation, cross-correlate the template with the sampled data, determine a time-of-arrival of the signal, decode the identifier from the sampled data, and use the time-of-arrival and the decoded identifier to determine information relating to the position

A system is provided for determining the position of a mobile receiver unit (7) in an environment (1). The system comprises a plurality of transmitter units (2, 3, 4, 5) which transmit a respective phase-modulated transmitter-unit identifier, a mobile receiver unit (7), arranged to receive a signal from a transmitter unit (2, 3, 4, 5), and a processing subsystem (205; 9). The processing subsystem (205; 9) is configured to sample received signals to generate sampled data, wherein the identifier spans a transmitter-unit-identifier-bearing portion of the sampled data, obtain template data corresponding to the identifier, analyse the sampled data to determine a Doppler-induced phase deviation, adjust the template or the sampled data to change one or more phase shifts by an amount depending on the determined deviation, cross-correlate the template with the sampled data, determine a time-of-arrival of the signal, decode the identifier from the sampled data, and use the time-of-arrival and the decoded identifier to determine information relating to the position

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.