Sonar bottom reacquisition systems and methods

1. A system comprising:

a sonar transducer assembly including a housing adapted to be mounted to a mobile structure;

a sonar transducer disposed within the housing; and

a logic device configured to communicate with the sonar transducer, wherein the logic device is configured to:

receive and process sonar data provided by the sonar transducer, the sonar data including data associated with a depth of a bottom surface in an underwater environment;

establish a bottom lock at the depth of the bottom surface based on the sonar data provided by the sonar transducer;

detect bottom lock loss of the bottom surface in the sonar data provided by the sonar transducer, based at least in part on a determination that the sonar data provided by the sonar transducer lacks acoustic returns corresponding to a bottom lock depth associated with the bottom lock;

determine a position of the mobile structure and/or of the sonar transducer;

determine an expected bottom depth associated with the detected bottom lock loss based at least in part on the determined position and bathymetric chart data of an area underlying at least the determined position; and

generate updated sonar data based, at least in part, on the expected bottom depth;

wherein the generating the updated sonar data comprises:

transmitting a sonar signal via the sonar transducer; and

monitoring a sounding acquisition time period for acoustic returns corresponding to the determined expected bottom depth, wherein the sounding acquisition time period is based, at least in part, on the expected bottom depth.

2. The system of claim 1 , wherein the logic device is further configured to determine the sonar data lacks the acoustic returns corresponding to the bottom lock depth by:

estimating a speed of ensonification for a water column beneath the sonar transducer;

transmitting a sonar signal via the sonar transducer;

monitoring a sounding acquisition time period for the acoustic returns corresponding to the bottom lock depth, wherein the sounding acquisition time period is based, at least in part, on the estimated speed of ensonification.

3. The system of claim 1 , wherein the logic device is further configured to determine the expected bottom depth by:

determining the position of the mobile structure and/or of the sonar transducer based, at least in part, on position data provided by a position sensor coupled to the mobile structure.

4. The system of claim 3 , further comprising the position sensor coupled to the mobile structure, wherein:

the bathymetric chart data is stored within a memory coupled to and/or integrated with the mobile structure or within a remote chart delivery server accessible wirelessly via a communications module coupled to and/or integrated with the mobile structure and/or a user interface of the mobile structure.

5. The system of claim 3 , wherein:

the expected bottom depth is determined based, at least in part, on interpolation of one or more cartographic spot soundings within the bathymetric chart data.

6. The system of claim 1 , wherein the logic device is further configured to generate the updated sonar data by:

estimating a speed of ensonification for a water column beneath the sonar transducer;

wherein the sounding acquisition time period is based, at least in part, on the estimated speed of ensonification.

7. The system of claim 6 , wherein the logic device is further configured to:

determine acoustic returns corresponding to the expected bottom depth are absent from the updated sonar data; and

generate further updated sonar data based, at least in part, on a set of test bottom depths, wherein:

the set of test bottom depths is based, at least in part, on a corresponding set of cartographic spot soundings of the bathymetric chart data that are within a predefined horizontal range of the position of the mobile structure.

8. The system of claim 1 , further comprising a user interface for the mobile structure, wherein the logic device is further configured to:

generate sonar image data based, at least in part, on the updated sonar data, wherein the sonar image data comprises an enhanced three dimensional (3D) and/or sidescan representation of an underwater environment associated with the mobile structure.

9. A method comprising:

processing sonar data provided by a sonar transducer disposed within a housing of a sonar transducer assembly mounted to a mobile structure, the sonar data including data associated with a depth of a bottom surface in an underwater environment;

establishing a bottom lock at the depth of the bottom surface under the mobile structure and/or a course of the mobile structure based on the sonar data provided by the sonar transducer;

detecting bottom lock loss of the bottom surface in the sonar data provided by the sonar transducer, based at least in part on a determination that the sonar data provided by the sonar transducer lacks acoustic returns corresponding to a bottom lock depth associated with the bottom lock;

determining a position of the mobile structure and/or of the sonar transducer;

determining an expected bottom depth associated with the detected bottom lock loss based at least in part on the determined position and bathymetric chart data of an area underlying at least the determined position and/or a course of the mobile structure; and

generating updated sonar data based, at least in part, on the expected bottom depth.

10. The method of claim 9 , wherein the determining the sonar data lacks the acoustic returns corresponding to the bottom lock depth comprises:

estimating a speed of ensonification for a water column beneath the sonar transducer;

transmitting a sonar signal via the sonar transducer;

monitoring a sounding acquisition time period for the acoustic returns corresponding to the bottom lock depth, wherein the sounding acquisition time period is based, at least in part, on the estimated speed of ensonification, the bottom lock depth, a start time of the transmitted sonar signal, and/or a temporal width of the transmitted sonar signal.

11. The method of claim 9 , wherein the determining the expected bottom depth comprises:

determining the position of the mobile structure and/or of the sonar transducer based, at least in part, on position data provided by a position sensor coupled to the mobile structure.

12. The method of claim 11 , wherein:

the bathymetric chart data is stored within a memory coupled to and/or integrated with the mobile structure or within a remote chart delivery server accessible wirelessly via a communications module coupled to and/or integrated with the mobile structure and/or a user interface of the mobile structure.

13. The method of claim 11 , wherein:

the determining the expected bottom depth is based, at least in part, on interpolation of one or more cartographic spot soundings within the bathymetric chart data.

14. The method of claim 9 , wherein the generating the updated sonar data comprises:

estimating a speed of ensonification for a water column beneath the sonar transducer;

wherein the sounding acquisition time period is based, at least in part, on the estimated speed of ensonification.

15. The method of claim 14 , further comprising:

determining acoustic returns corresponding to the expected bottom depth are absent from the updated sonar data; and

generating further updated sonar data based, at least in part, on a set of test bottom depths, wherein:

the set of test bottom depths is based, at least in part, on a corresponding set of cartographic spot soundings of the bathymetric chart data that are within a predefined horizontal range of the position of the mobile structure.

16. The method of claim 9 , further comprising:

generating sonar image data based, at least in part, on the updated sonar data, wherein the sonar image data comprises an enhanced three dimensional (3D) and/or sidescan representation of an underwater environment associated with the mobile structure.