Abstract: A method for reliably locating the position of a submerged submarine with spect to a surface ship. A multiple number of transponders are placed at known locations near the sea floor, in the area of the ship and the submarine. One transponder has a dual function both as a response transponder and as a relay transponder. The other transponders have a single function as response transponders. Elapsed times between transmission of a first acoustic transmission pulse from the ship and receptions of first acoustic response pulses coming from the transponders, are measured at the ship. Elapsed times between transmission of a second acoustic pulse from the ship, its relay through the relay transponder, a response to the relayed signal by the submarine and then responses to the submarine's response pulse by the transponders, are also measured at the ship. These elapsed times are used to determine distances between the ship and the transponders, and distances between the transponders and the submarine.

Abstract: A position and velocity determining system, that uses two functioned receiver-transmitters. In performing a first function, each receiver-transmitter transmits an acoustic pulse at a unique frequency, in response to a first received accoustic pulse. In performing a second function, each receiver-transmitter transmits a continuous acoustic signal at a unique frequency, in response to a second received acoustic pulse.

Abstract: A system for acoustically positioning a noisy platform. An array of transponders, adapted to be deployed in a region of water, is provided. A transducer is mounted on the noisy platform and another transducer is mounted on a relatively quiet vehicle tethered to the platform. A first means is provided for transmitting acoustical energy from the transducer on the noisy platform to said array and from said array to said transducer on said vehicle for measuring the distance from said noisy platform to said quiet vehicle via said transponders in said array. A second means is provided for transmitting acoustical energy from the transducer on said vehicle to said array and back to said vehicle for measuring the distance said vehicle is from the transponders in said array. Calculating means is coupled to said first and second means for determining the location of said noisy platform relative to said array.

Abstract: A ranging system employing a limiting constant false alarm rate (CFAR) receiver having reduced recognition time uncertainty, or recognition jitter. The jitter is made proportional to signal-to-noise ratio by providing the receiver with a two-part signal. A conditioning signal is provided to the receiver prior to the time the receiver is expected to sense and respond to a recognition signal for ranging. The conditioning signal has selected strength and duration sufficient to suppress noise to a desired extent in the receiver at the time the recognition signal is received. The combination of strength and frequency of the conditioning signal is selected so as to limit the probability of a false alarm, or undesired recognition of the conditioning signal in the receiver. Receiver modification is not required.

Abstract: An arrangement for determining the relative three dimensional positional relationship, including the horizontal separation, location, and orientation between a plurality of underwater transponders. A plurality of underwater transponders are positioned adjacent the bottom of the body of water and the number of the plurality of transponders for an unambiguous determination comprises at least three. In one embodiment, each of the transponders is provided with structure to receive a first interrogation frequency signal and generate a unique output signal in response thereto. Additionally, a first of the transponders also is provided with structure to generate the first interrogation frequency signal in response to a second interrogation frequency signal. A second of the plurality of transponders is provided with structure to generate the first interrogation frequency signal in response to a third interrogation frequency signal.