System and processor for real-time extraction of ocean bottom properties

• US 5,568,450 A
• Filed: 10/18/1994
• Issued: 10/22/1996
• Est. Priority Date: 10/18/1994
• Status: Expired due to Fees

• Current Assignee: The Government Of The United States As Represented By The Secretary Of The Navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Sundvik, Michael T., Grande, David W., Bishop, Judith L., Cole, Bernard F.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US08/330,143
• Time in Patent Office: 735 Days
• Field of Search: 367/87, 367/131, 367/88, 364/421
• US Class Current: 367/131
• CPC Class Codes: G01S 15/86 Combinations of sonar systems with lidar systems; Combinations of sonar systems with systems not using wave reflection
• CPC Class Codes: G01S 15/89 for mapping or imaging
• CPC Class Codes: G01S 7/52004 Means for monitoring or calibrating short-range imaging G01S7/5205
• CPC Class Codes: G01S 7/527 Extracting wanted echo signals Doppler systems G01S15/50
• CPC Class Codes: G01S 7/53 Means for transforming coordinates or for evaluating data, e.g. using computers
• CPC Class Codes: H04B 11/00 Transmission systems employing sonic, ultrasonic or infrasonic waves
• CPC Class Codes: H04B 13/02 Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy

Abstract

A system for characterizing ocean bottom properties in real-time by explong the multipath structure of reverberation to extract values for the bottom loss and the bottom scattering coefficient. The system obtains environmental and navigational data and synchronizes the data with sonar state data and acoustic beam data to produce an input data stream to an extraction processor. The extraction processor utilizes a digital signal processing means to produce a reverberation energy envelope from the acoustic beam data and time correlate the reverberation energy envelope with the environmental, navigational, and sonar state data. A general purpose computer monitors the reverberation envelope and the environmental, navigational, and sonar state data for change and instructs a modeling processor to construct a new eigenray propagation model and a new reference reverberation model if any changes occur in the data that results in a change to the previously constructed eigenray propagation or reference reverberation models. A pair of local extraction processors perform the extraction of the bottom loss and the bottom scattering coefficient by performing a probe pulse extraction algorithm and a reverberation decay algorithm, respectively.

Claims

1. A processor for characterizing ocean bottom parameters in real-time comprising:

signal processing means for receiving navigational, environmental, and sonar data and processing said data into a reverberation energy envelope, said reverberation energy envelope being generated from an acoustic return from a sonar ping, and into blocks of time correlated data;

data monitoring means, coupled to said signal processing means, for monitoring said navigational, environmental, and sonar state data and said reverberation energy envelope for changes; and

model processing means, responsive to said data monitoring means, for building a set of acoustic model eigenrays, building a reference reverberation model, said reference reverberation model comprising reference reverberation as a function of time, and extracting bottom parameters by comparing said reverberation energy envelope with said reference reverberation model.

2. The processor of claim 1 wherein said model processing means comprises:

model generating means for generating said set of acoustic model eigenrays and said reference reverberation model;

probe pulse extraction means for determining individual reverberation values for a number of acoustic paths, said paths being selected from said set of acoustic model eigenrays, and for comparing said individual reverberation values with said reverberation energy envelope to extract bottom parameters; and

decay extraction means for identifying a time period wherein said reverberation energy envelope exhibits a characteristic decay rate and for analyzing said reference reverberation and said reverberation energy envelope within said time period to extract bottom parameters.

3. The processor of claim 2 wherein said data monitoring means comprises:

signal processor managing means for controlling the time correlation of said navigational, environmental, and sonar data, for managing the processing of said reverberation energy envelope, and for directing transfer of said data and said reverberation energy envelope between said data monitoring means and said signal processing means;

reverberation post processing means for analyzing two or more reverberation energy envelopes to identify changes within said reverberation energy envelopes caused by a change in said navigational, environmental, and sonar data; and

system managing means for monitoring said reverberation post processing means and for managing communication with said model processing means.

4. The processor of claim 3 wherein said signal processing means comprises:

signal conditioning means for receiving said navigational, environmental, and sonar data, time correlating said navigational, environmental, and sonar data, and separating said sonar data into acoustic beam data and sonar state data; and

reverberation processing means for processing said acoustic beam data into said reverberation energy envelope.

5. A system for characterizing ocean bottom parameters in real-time comprising:

sensing means for obtaining navigational and environmental data including position coordinates, heading, speed, wind direction and velocity, and water temperature a depth data;

a sonar system producing sonar state data corresponding to the configuration of said sonar system and acoustic beam data corresponding to sound received at a sonar array;

data acquisition means for producing a data stream, said data stream comprising said navigational, environmental and sonar state data multiplexed with said acoustic beam data;

signal processing means for receiving said data stream, processing said acoustic beam data into a reverberation energy envelope, said reverberation energy envelope being generated from an acoustic return from a sonar ping, and correlating said navigational, environmental, and sonar state data with said reverberation energy envelope over a common time domain;

data monitoring means, coupled to said signal processing means, for monitoring said navigational, environmental and sonar state data and said reverberation energy envelope for changes; and

model processing means, responsive to said data monitoring means, for building a set of acoustic model eigenray, building a reference reverberation model, said reference reverberation mode, comprising reference reverberation as a function of time, and extracting bottom parameters by comparing said reverberation energy envelope with said reference reverberation model.

6. The system of claim 5 wherein said model processing means comprises:

model generating means for generating said set of acoustic model eigenrays and said reference reverberation model;

probe pulse extraction means for determining individual reverberation values for a number of acoustic paths, said paths being selected from said set of acoustic model eigenrays, and for comparing said individual reverberation values with said reverberation energy envelope to extract bottom parameters; and

decay extraction means for identifying a time period wherein said reverberation energy envelope exhibits a characteristic decay rate and for analyzing said reference reverberation and said reverberation energy envelope within said time period to extract bottom parameters.

7. The system of claim 6 wherein said data monitoring means comprises:

signal processor managing means for controlling the time correlation of said navigational, environmental, and sonar state data with said reverberation energy envelope, for managing the processing of said reverberation energy envelope, and for directing transfer of said data and said reverberation energy envelope between said data monitoring means and said signal processing means;

reverberation post processing means for analyzing two or more reverberation energy envelopes to identify changes within said reverberation energy envelopes caused by a change in said navigational, environmental, and sonar state data; and

system managing means for monitoring said reverberation post processing means and for managing communication with said model processing means.

8. The system of claim 7 wherein said signal processing means comprises:

signal conditioning means for receiving said navigational, environmental, and sonar state data, time correlating said navigational, environmental, and sonar data, and separating said sonar data into acoustic beam data and sonar state data; and

reverberation processing means for processing said acoustic beam data into said reverberation energy envelope.