SYSTEM FOR MEASURING A TIME OFFSET AND METHOD OF MEASURING A TIME OFFSET
First Claim
1. A system for measuring a time offset of an acoustic sensor node relative to a reference time, the system comprising:
- an acoustic communications unit arranged to transmit a first acoustic probe signal to the acoustic sensor node;
a processing resource operably coupled to the acoustic communications unit and arranged to record a transmission time of the first signal, the transmission time being relative to the reference time;
whereinthe acoustic sensor node is arranged to receive the first signal and to transmit a second acoustic reply signal to the acoustic communications unit after a predetermined time delay, the second signal including time data indicative of a current internal time of the acoustic sensor node during the predetermined time delay; and
the acoustic communications unit is arranged to receive the second signal, the processing resource recording a receive time at which the second signal is received, the receive time also being relative to the reference time, and to calculate the combined time of flight of the first and second signals, and using the combined time of flight and the predetermined time delay to calculate the time offset between the current internal time of the sensor node and the reference time.
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Accused Products
Abstract
A system and method measures the time offsets of a plurality of acoustic sensor nodes relative to a reference time. The system includes an acoustic transceiver arranged to transmit a first signal to each acoustic sensor node and a processing resource arranged to record the transmission time of the first signal relative to the reference time. The acoustic sensor nodes receive the first signal and transmit a return second signal to the acoustic transceiver after a predetermined time delay, the second signal including the current acoustic sensor node internal time. The acoustic transceiver receives the second signal, and the processing resource records the time at which the second signal was received relative to the reference time and records also the combined time of flight of the first and second signal. From this data the time offset between the sensor node internal time and the reference time is calculated.
22 Citations
20 Claims
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1. A system for measuring a time offset of an acoustic sensor node relative to a reference time, the system comprising:
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an acoustic communications unit arranged to transmit a first acoustic probe signal to the acoustic sensor node; a processing resource operably coupled to the acoustic communications unit and arranged to record a transmission time of the first signal, the transmission time being relative to the reference time;
whereinthe acoustic sensor node is arranged to receive the first signal and to transmit a second acoustic reply signal to the acoustic communications unit after a predetermined time delay, the second signal including time data indicative of a current internal time of the acoustic sensor node during the predetermined time delay; and the acoustic communications unit is arranged to receive the second signal, the processing resource recording a receive time at which the second signal is received, the receive time also being relative to the reference time, and to calculate the combined time of flight of the first and second signals, and using the combined time of flight and the predetermined time delay to calculate the time offset between the current internal time of the sensor node and the reference time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A subsea seismic survey system comprising:
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a plurality of acoustic seismic sensor nodes; a surface vessel;
whereinthe surface vessel comprises an acoustic communications unit arranged to transmit a first acoustic probe signal to the plurality of acoustic sensor nodes and a processing resource operably coupled to the acoustic communications unit and arranged to record a transmission time of the first signal, the transmission time being relative to the reference time; the plurality of acoustic sensor nodes are arranged to receive the first signal and to transmit a second acoustic reply signal to the acoustic communications unit after a predetermined time delay, the second signal including time data indicative of a current internal time of the acoustic sensor node during the predetermined time delay; and the acoustic communications unit is arranged to receive the second signal, the processing resource recording a receive time at which the second signal is received, the receive time also being relative to the reference time, and to calculate the combined time of flight of the first and second signals, and using the combined time of flight and the predetermined time delay to calculate the time offset between the current internal time of the sensor node and the reference time.
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11. A method of measuring a time offset of an acoustic sensor node relative to a reference time, the method comprising:
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transmitting a first acoustic probe signal to the acoustic sensor node from an acoustic communications unit; recording a transmission time of the first signal, the transmission time being relative to the reference time; the acoustic sensor node receiving the first signal and transmitting a second acoustic reply signal to the acoustic communications unit after a predetermined time delay, the second signal including time data indicative of a current internal time of the acoustic sensor node; and the acoustic communications unit receiving the second signal and recording a receive time at which the second signal is received, the receive time also being relative to the reference time, and calculating the combined time of flight of the first and second signals, and using the combined time of flight and the predetermined time delay to calculate the time offset between the current internal time of the sensor node and the reference time. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification