Downscan imaging sonar

Abstract

A downscan imaging sonar utilizes a linear transducer element to provide improved images of the sea floor and other objects in the water column beneath a vessel. A transducer array may include a plurality of transducer elements and each one of the plurality of transducer elements may include a substantially rectangular shape configured to produce a sonar beam having a beamwidth in a direction parallel to longitudinal length of the transducer elements that is significantly less than a beamwidth of the sonar beam in a direction perpendicular to the longitudinal length of the transducer elements. The plurality of transducer elements may be positioned such that longitudinal lengths of at least two of the plurality of transducer elements are parallel to each other. The plurality of transducer elements may also include at least a first linear transducer element, a second linear transducer element and a third linear transducer element.

1 .- 57 . (canceled) 
     
     
         58 . A sonar transducer assembly for imaging an underwater environment beneath a watercraft, the sonar transducer assembly comprising:
 a housing mountable to the watercraft, wherein the watercraft defines a center plane that extends from fore to aft of the watercraft; and   a linear downscan transducer element positioned within the housing, wherein the linear downscan transducer element is configured to produce a fan-shaped sonar beam having a relatively narrow beamwidth in a direction parallel to a longitudinal length of the linear downscan transducer element and a relatively wide beamwidth in a direction perpendicular to the longitudinal length of the linear downscan transducer element, wherein the linear downscan transducer element is positioned with the longitudinal length thereof extending in a fore-to-aft direction of the housing, wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam such that the relatively wide beamwidth spans across the center plane of the watercraft to cover directly beneath the watercraft.   
     
     
         59 . The sonar transducer assembly of  claim 58 , wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam such that at least a portion of the relatively wide beamwidth spans on each side of the center plane of the watercraft. 
     
     
         60 . The sonar transducer assembly of  claim 58 , wherein the fan-shaped sonar beam produced by the linear downscan transducer element is defined by theoretical boundaries that correspond to half power points for the fan-shaped sonar beam. 
     
     
         61 . The sonar transducer assembly of  claim 60 , wherein the half power points are −3 dB. 
     
     
         62 . The sonar transducer assembly of  claim 58 , wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam to extend out to both sides of the center plane and cover a water column beneath the watercraft. 
     
     
         63 . The sonar transducer assembly of  claim 58 , wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam such that a widest portion of the relatively wide beamwidth is centered at the center plane. 
     
     
         64 . The sonar transducer assembly of  claim 58 , further comprising a second downscan transducer element positioned within the housing, the second downscan transducer element being configured to produce a generally conical beam that is wider than the fan-shaped sonar beam in a direction parallel to a longitudinal length of the linear downscan transducer element, wherein the second downscan transducer element is positioned within the housing to project the conical beam to cover directly beneath the watercraft. 
     
     
         65 . The sonar transducer assembly of  claim 58 , further comprising:
 a first linear sidescan transducer element positioned within the housing and configured to produce a fan-shaped sonar beam, wherein the first linear sidescan transducer element is positioned within the housing to project the fan-shaped sonar beam to a first side of the center plane, wherein the first side of the center plane corresponds generally to a starboard side of the watercraft; and   a second linear sidescan transducer element positioned within the housing and configured to produce a fan-shaped sonar beam, wherein the second linear sidescan transducer element is positioned within the housing to project the fan-shaped sonar beam to a second side of the center plane, wherein the second side of the center plane corresponds generally to a port side of the watercraft.   
     
     
         66 . A sonar system comprising:
 a sonar transducer assembly for imaging an underwater environment beneath a watercraft, the sonar transducer assembly comprising:
 a housing mountable to the watercraft, wherein the watercraft defines a center plane that extends from fore to aft of the watercraft; and 
 a linear downscan transducer element positioned within the housing, wherein the linear downscan transducer element is configured to produce a fan-shaped sonar beam having a relatively narrow beamwidth in a direction parallel to a longitudinal length of the linear downscan transducer element and a relatively wide beamwidth in a direction perpendicular to the longitudinal length of the linear downscan transducer element, wherein the linear downscan transducer element is positioned with the longitudinal length thereof extending in a fore-to-aft direction of the housing, wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam such that the relatively wide beamwidth spans across the center plane of the watercraft to cover directly beneath the watercraft; 
   a sonar signal processor configured to receive linear downscan sonar data from the linear downscan transducer element based on sonar returns from the fan-shaped sonar beam produced by the linear downscan transducer element; and   a display configured to present an image corresponding to the linear downscan sonar data.   
     
     
         67 . The sonar system of  claim 66 , wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam such that at least a portion of the relatively wide beamwidth spans on each side of the center plane of the watercraft. 
     
     
         68 . The sonar system of  claim 66 , wherein the fan-shaped sonar beam produced by the linear downscan transducer element is defined by theoretical boundaries that correspond to half power points for the fan-shaped sonar beam. 
     
     
         69 . The sonar system of  claim 68 , wherein the half power points are −3 dB. 
     
     
         70 . The sonar system of  claim 66 , wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam to extend out to both sides of the center plane and cover a water column beneath the watercraft. 
     
     
         71 . The sonar system of  claim 66 , wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam such that a widest portion of the relatively wide beamwidth is centered at the center plane. 
     
     
         72 . The sonar system of  claim 66 , wherein the sonar transducer assembly further comprises a second downscan transducer element positioned within the housing, the second downscan transducer element being configured to produce a generally conical beam that is wider than the fan-shaped sonar beam in a direction parallel to a longitudinal length of the linear downscan transducer element, wherein the second downscan transducer element is positioned within the housing to project the conical beam to cover directly beneath the watercraft, wherein the sonar signal processor is configured to receive second downscan sonar data from the second downscan transducer element based on sonar returns from the conical sonar beam produced by the second downscan transducer element. 
     
     
         73 . The sonar system of  claim 66 , wherein the sonar transducer assembly further comprises:
 a first linear sidescan transducer element positioned within the housing and configured to produce a fan-shaped sonar beam, wherein the first linear sidescan transducer element is positioned within the housing to project the fan-shaped sonar beam to a first side of the center plane, wherein the first side of the center plane corresponds generally to a starboard side of the watercraft; and   a second linear sidescan transducer element positioned within the housing and configured to produce a fan-shaped sonar beam, wherein the second linear sidescan transducer element is positioned within the housing to project the fan-shaped sonar beam to a second side of the center plane, wherein the second side of the center plane corresponds generally to a port side of the watercraft; and   wherein the sonar signal processor is configured to receive first linear sidescan sonar data from the first linear sidescan transducer element based on sonar returns from the fan-shaped sonar beam produced by the first linear sidescan transducer element, wherein the sonar signal processor is configured to receive second linear sidescan sonar data from the second linear sidescan transducer element based on sonar returns from the fan-shaped sonar beam produced by the second linear sidescan transducer element.   
     
     
         74 . A method of operating a sonar system, the method comprising:
 providing a sonar transducer assembly for imaging an underwater environment beneath a watercraft, wherein the sonar transducer assembly comprises:
 a housing mountable to the watercraft, wherein the watercraft defines a center plane that extends from fore to aft of the watercraft; and 
 a linear downscan transducer element positioned within the housing, wherein the linear downscan transducer element is configured to produce a fan-shaped sonar beam having a relatively narrow beamwidth in a direction parallel to a longitudinal length of the linear downscan transducer element and a relatively wide beamwidth in a direction perpendicular to the longitudinal length of the linear downscan transducer element, wherein the linear downscan transducer element is positioned with the longitudinal length thereof extending in a fore-to-aft direction of the housing, wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam such that the relatively wide beamwidth spans across the center plane of the watercraft to cover directly beneath the watercraft; 
   causing projection of a fan-shaped sonar beam from the linear downscan transducer element; and   receiving sonar returns from the underwater environment based on the fan-shaped sonar beam projected from the linear downscan transducer element.   
     
     
         75 . The method of  claim 74  further comprising:
 providing a sonar signal processor; and 
 receiving, at the sonar signal processor, linear downscan sonar data from the linear downscan transducer element based on sonar returns from the fan-shaped sonar beam produced by the linear downscan transducer element. 
 
     
     
         76 . The method of  claim 75  further comprising:
 providing a display; 
 processing, via the sonar signal processor, the linear downscan sonar data to generate an image corresponding to the linear downscan sonar data; and 
 causing presentation of the image on the display. 
 
     
     
         77 . The method of  claim 74 , wherein the linear downscan transducer element is positioned within the housing to project the fan-shaped sonar beam such that at least a portion of the relatively wide beamwidth spans on each side of the center plane of the watercraft.