Abstract: A method and apparatus are provided for estimating the water speed of a first acoustic node D belonging to a network of acoustic nodes, at least some of the acoustic nodes being arranged along towed acoustic linear antennas (S). The method includes steps of: a) defining a N-dimensional base, the center of which is the first acoustic node and comprising a single axis, when N=1, or N non-collinear axes, when N=2 or N=3, each axis being associated with a base vector extending from the first acoustic node to another acoustic node; and b) estimating an amplitude of the water speed, as a function of: for each given other acoustic node defining the base vector: an acoustic propagation duration of an acoustic signal transmitted from the first acoustic node to the given other acoustic node, and an acoustic propagation duration of an acoustic signal transmitted from the given other acoustic nodes to the first acoustic node; and a value c of the underwater acoustic sound velocity.

Abstract: A method and apparatus are provided for estimating the water speed of a first acoustic node D belonging to a network of acoustic nodes, at least some of the acoustic nodes being arranged along towed acoustic linear antennas (S). The method includes steps of: a) defining a N-dimensional base, the center of which is the first acoustic node and comprising a single axis, when N=1, or N non-collinear axes, when N=2 or N=3, each axis being associated with a base vector extending from the first acoustic node to another acoustic node; and b) estimating an amplitude of the water speed, as a function of: for each given other acoustic node defining the base vector: an acoustic propagation duration of an acoustic signal transmitted from the first acoustic node to the given other acoustic node, and an acoustic propagation duration of an acoustic signal transmitted from the given other acoustic nodes to the first acoustic node; and a value c of the underwater acoustic sound velocity.

Abstract: A method for obtaining a node-to-surface distance between a reference surface and a first node belonging to a network of a plurality of nodes arranged along towed acoustic linear antennas. A plurality of acoustic sequences are sent between the nodes. Each sequence is used to estimate an inter-node distance as a function of a propagation duration of the sequence between nodes. After emission by the first node of a given signal: the first node measures a first propagation duration of a first reflection by the reference surface of the given signal, and a first value of the node-to-surface distance is obtained as a function of that first propagation duration; and/or a second node measures a second propagation duration of a second reflection by the reference surface of the given signal, and a second value of the node-to-surface distance is obtained as a function of that second propagation duration.

Abstract: The invention relates to a mobile device for emitting seismic vibrations into the ground in order to collect geophysical data, said device comprising at least two mobile platforms, each provided with a vibrating pad that vibrates in such a way as to propagate seismic waves in the ground when said vibrating pad is brought into contact with the ground at a desired spot. The inventive device is characterised in that the mobile platforms are interconnected in order to form a train of platforms in which the distance between the vibrating pads of said mobile platforms is controlled.

Abstract: A seismic data acquisition unit includes a data acquisition and digital circuit which receives an analog seismic signal and digitizes the signal. The digitized seismic data uses data telemetry and a repeater device to receive the compressed data and transmit the compressed data to a seismic central control unit. The data decompressor takes the data from the data compressor and decompresses the data. The decompressed data is then compared with the original digitized data to determine the amount of noise resulting from the compression process. The compression noise is compared to the ambient noise, and if the compression noise exceeds a predefined criterion, then the compression ratio in the data compressor is adjusted for a lower degree of compression. The process is repeated until the amount of compression noise, relative to ambient noise, is satisfactory.

Abstract: A seismic data acquisition unit includes a data acquisition and digitizer which receives an analog seismic signal and digitizes the signal. The data acquisition and digitizer also acquires an ambient noise signal at some point in the data acquisition and recording signal at a time when ambient noise is not masked by the seismic signal. The data acquisition unit further comprises a data compressor to receive the digitized signal from the data acquisition and digitizer and compress the digitized data, preferably with a lossy compression algorithm. Finally, the data acquisition unit comprises a data telemetry and repeater device to receive the compressed data and transmit the compressed data to a central unit. The data acquisition unit preferably includes a data decompressor. The data decompressor takes the data from the data compressor and decompresses the data. The decompressed data is then compared with the original digitized data to determine the amount of noise which resulted from the compression process.