METHOD OF MONITORING THE POSITION OF TOWED UNDERWATER APPARATUS

• US 3,860,900 A
• Filed: 02/21/1973
• Issued: 01/14/1975
• Est. Priority Date: 02/21/1973
• Status: Expired due to Term

• Current Assignee: AT&T, Inc.
• Original Assignee: Ronald J. Scudder
• Inventors: Scudder, Ronald J.
• Primary Examiner(s): Farley, Richard A.
• Application Number:
  US05/334,320
• Time in Patent Office: 692 Days
• Field of Search: 340/2,3R,3T,3E,5R,6R
• US Class Current: 367/6
• CPC Class Codes: G01S 15/874 Combination of several spaced transponders or reflectors of known location for determining the position of a receiver G01S15/872 takes precedence

Abstract

The three-dimensional position (geographic position and depth) of equipment towed underwater by a moving ship is continually and precisely monitored by an acoustic system that includes a network of underwater, acoustic transponders, and a remote, batterypowered, acoustic interrogation transducer that is associated with the suspended equipment. Initially a combination of satellite fixes of the ship'"'"''"'"'s position and direct interrogation of the transponders from the ship are utilized by a shipboard computer system to determine the three-dimensional position of the transponders. Then, as the ship moves about above the transponder network towing the equipment, the transponders are periodically interrogated from the ship. The resulting acoustic travel with the previously calculated positions of the transponders to continually compute and predict the geographic position of the ship. The remote interrogation transducer is also periodically command interrogated from the ship and thereby actuated both to respond to the ship and to interrogate the transponders, which respond to the ship. The resulting acoustic travel times, the positions of the transponders, and the predicted positions of the ship are utilized by the computer system to monitor the three-dimensional position of the remote interrogation transducer and the towed equipment.

Claims

1. A method of monitoring the three-dimensional position of equipment towed underwater from a ship geographically positioned within the approximate geographic area bounded by an underwater network of at least three acoustic transponders of known geographic position and depth, the method comprising the steps of:

interrogating the transponders directly from the ship to determine acoustic travel times between the ship and the transponders;

fixing the geographic position of the ship relative to the transponders at the time of direct interrogation from the depths of the transponders and the direct interrogation acoustic travel times;

interrogating a remote-powered acoustic interrogation transducer associated with the towed equipment to determine acoustic travel times between the ship and the towed equipment and to interrogate each of the transponders by the interrogation transducer to determine acoustic travel times from the ship to the towed equipment to each of the transponders and back to the ship; and

fixing the three-dimensional position of the towed equipment relative to the ship from the geographic posiTion of the ship, the depth of the transponders and the acoustic travel times between the ship and the towed equipment and the acoustic travel times from the ship to the towed equipment to each of the transponders and back to the ship.

2. The method of claim 1, wherein fixing the geographic position of the ship at the time of direct interrogation comprises the steps of:

converting the direct interrogation acoustic travel times between the ship and the transponders to slant ranges;

computing a horizontal range between the ship and the transponders from the slant ranges and the depth of the transponders; and

converting the horizontal ranges to the geographic position of the ship relative to the geographic positions of the transponders.

3. The method of claim 1, wherein fixing the three-dimensional position of the towed equipment at the time of remote interrogation comprises the steps of:

predicting a position of the ship at the time of remote interrogation from the geographic position of the ship at the time of the direct interrogation;

determining a one way acoustic travel time (tR) between the ship and the remote interrogation transducer and therefore the towed equipment associated therewith;

predicting the acoustic travel time (tiS) from each of the transponders to the ship from the predicted geographic position of the ship and the position of the transponders;

determining an acoustic travel time (tRi) between the remote interrogation transducer and each transponder by subtracting the acoustic travel time (tR) and the predicted acoustic travel time (tiS) for each of the transponders from the total acoustic travel times from the ship to the remote interrogation transducer to each of the transponders and back to the ship;

determining slant ranges (SRi) from the remote interrogation transducer to each transponder from the acoustic travel times (tRi); and

determining the three-dimensional position of the towed equipment from the slant ranges (SRi) the depth of the transponders and the geographic position of the transponders.

4. A method of monitoring the three-dimensional position of underwater equipment towed by a ship, comprising:

bottom mounting at least three transponders to bound a predetermined geographic area;

steaming across each transponder while interrogating the transponders to determine a minimum acoustic travel time from the ship to each transponder;

converting the minimum acoustic travel times to a depth for each transponder;

steaming at right angles to a line joining a pair of transponders while interrogating the transponders to determine the minimum acoustic travel times between the ship and the transponders;

repeating the foregoing step for each pair of transponders;

converting the minimum acoustic travel times between the ship and each transponder of each pair of transponders to a horizontal range between each pair of transponders;

fixing a geographic position of the transponders relative to a position of the ship from the depth of and horizontal ranges between the transponders;

interrogating the transponders directly from the ship to determine acoustic travel times between the ship and each transponder;

fixing a geographic position of the ship relative to the transponders at the time of direct interrogation from the depths and geographic position of the transponders and the direct interrogation acoustic travel times;

interrogating a remote-powered acoustic interrogation transducer associated with the towed equipment to determine acoustic travel times between the ship and the towed equipment and to interrogate each of the transponders by the interrogation transducer to determine acoustic travel times from the ship to the towed equipment to each of the transponders and back to the ship; and

fixing the three-dimensional position of the towed equipment relative to the ship from the geographic position of the ship, the depth of the transponders and the acoustic travel times between the ship and the towed equipment and the acoustic travel times from the ship to the towed equipment to each of the transponders and back to the ship.