Ion Geophysical Corporation

Input/output, Inc.

Clem B Guillot, Iii

Robert E Rouquette

Dale J Lambert

Daniel B Seale

Robert H Kemp, Jr

A two-tier communication system for a seismic streamer. The communication system operates over an unshielded twisted-pair communication line extending the length of the streamer. Repeater units having a repeater function and a device controller function divide the twisted pair into line segments. Coils on each segment couple signals inductively to collocated external devices in a low-speed 2400 baud FSK data link between the devices and an associated device controller. A Gaussian 8-level FSK high-speed 60 kbit/s data link is established along all the segments with the repeaters re-transmitting boosted signals along the entire length of the communication line. The coils are transparent at the high-speed data rate. Time division multiple access (TDMA) or frequency division multiple access (FDMA) is used to accommodate the two links on the single twisted pair.

Two-tier streamer communication system

A GPS-based underwater cable positioning system for use in determining the shape and position of hydrophone streamers towed underwater behind survey vessels involved in marine seismic prospecting. The system includes a plurality of surface units towed behind the vessel. Each surface unit includes a GPS receiver to receive radio frequency GPS signals and to determine its positions. Each surface unit also has an acoustic transmitter to transmit an acoustic message signal representing its position and an optional time stamp into the water. Acoustic receiver units, attached spaced apart locations along one or more streamer cables, each include an acoustic receiver to receive the acoustic message signals from the surface units and to determine its position from the message signals. To augment the message signals from the surface units at locations distant from the surface units, acoustic transceiver units may be used. The acoustic transceiver units are attached to the streamer cables at ranges between the surface units and distant acoustic receiver units. The acoustic transceiver units each include an acoustic receiver that performs as the receivers in the acoustic receiver units and an acoustic transmitter to transmit acoustic message signals representing its position and an optional time stamp into the water to be received by the acoustic receiver units. In this way, the positions and shapes of towed streamer cables can be determined.

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Thibodaux, LA, United States of America

Clem B Guillot, Iii