Microprocessor-based apparatus and method for determining the distance between an object and a reference position. An embodiment of a graphical digitizer is set forth in which a microprocessor system (100) is adapted to generate and store a count that depends upon the number of instruction cycles that the microprocessor system (100) performs during a time interval that is a function of travel time of acoustic wave energy traveling between the object and the reference position. In a disclosed embodiment, acoustic receivers (A & B) are mounted with their axes parallel, and each receiver has a generally circular receptivity pattern.

Distance ranging apparatus and method

Apparatus (50) for deploying an object to an underwater target position, the apparatus being provided with a beacon to transmit acoustic rays, a plurality of thrusters (56(i), i = 1, 2, ...I, I being an integer) to control positioning of said apparatus with respect to said underwater target position, and a sound velocity meter to measure velocity of sound in a fluid surrounding said apparatus.

Apparatus for deploying a load to an underwater target position with enhanced accuracy and a method to control such apparatus

A technique facilitates the use of seismic data. The technique utilizes an autonomous underwater vehicle to obtain data on water column characteristics in a seismic survey area. The data can be used to adjust aspects of the seismic survey data and/or the seismic survey technique.

System and method of using autonomous underwater vehicle to facilitate seismic data acquisition

For mapping and exploring bodies of water, fan depth finders are used that emit ultrasound pulses and receive-echo pulses in a number of tightly-bundled receiving sectors. Because the predominant number of receiving directions is oriented diagonally downward instead of straight down, these ultrasound pulses propagate on bent paths due to sound refraction. Sound refraction is caused by different sound velocity layers, the precise knowledge of which is necessary for determining an average sound velocity. The method of the present invention does not require a separate measuring probe to measure the sound velocity at different depths; rather, the average sound velocity is determined using a regression method based on the travel time measurements of the ultrasound pulses. In this method, first the floor profile that forms the basis of the measured travel times is determined with an assumed average sound velocity and compared with a floor profile model composed of partial functions modeled in a specific manner. Because a correction value for the average sound velocity can be determined from the partial functions, improved depth values of the floor profile can be determined iteratively with the measured travel times and the corrected sound velocity. A method of this type can advantageously be implemented on research and survey vessels for attaining the high precision required in surveying technology.

Method for determining the depth values of a body of water

One embodiment of the invention concerns a probe that couples to a seismic vessel via a tow cable. When deploying probes from a seismic vessel that is towing source arrays and streamers, the probe and its tow cable can tangle with elements of the towed seismic spread. However, a cable guide may be used to lessen the risk for such entanglement by guiding the tow cable into the water at a distance removed from the seismic spread. Also, the probe may be steerable to steer the probe and tow cable away from the seismic spread. Other embodiments are described herein.

Collision avoidance for instrumented probes deployed from a seismic vessel

A digital apparatus for determining the velocity of sound at a selected position in a liquid media is provided with a means for representing the conductivity, temperature and depth of the position in the form of digital numbers, and provides a digital calculating means receiving each of the digital numbers for calculating the velocity of sound as a function of conductivity, temperature, and depth. The sound velocity may be calculated at a succession of positions to provide sound velocity versus depth profile of the liquid media.

Digital sound velocity calculator

An analog apparatus for determining the velocity of sound at a selected position in a liquid media is provided with a means for representing the conductivity, temperature, and depth of the position in the form of analog voltages, and is further provided with an analog calculating means receiving each of the voltages for calculating the velocity of sound as a function of conductivity, temperature, and depth. The sound velocity may be calculated at a succession of positions to provide a sound velocity versus depth profile of the liquid media.

Dan M. Griffin

Papers

Digital sound velocity calculator

Analog sound velocity calculator