Forming a composite down sonar image

1. An apparatus for providing marine information, the apparatus comprising:

a user interface;

a processor; and

a memory including computer program code, the memory and the computer program code configured to, with the processor, cause the apparatus to:

receive first side facing sonar returns from at least one first side facing transducer received from an underwater environment relative to a first side of a vessel;

receive second side facing sonar returns from at least one second side facing transducer received from the underwater environment relative to a second side of the vessel, wherein the second side of the vessel is opposite the first side of the vessel;

generate a composite down facing sonar image formed based on historical one-dimensional sonar data taken over time from both of the first side facing sonar returns and the second side facing returns, wherein the down facing sonar image is formed of at least:

a first sonar image slice that is generated based on a composite of the first side facing sonar returns and the second side facing sonar returns taken at a first time; and

a second sonar image slice that is generated based on a composite of the first side facing sonar returns and the second side facing sonar returns taken at a second time, where the second time is different than the first time, wherein the down facing sonar image is built up of at least the first sonar image slice extending downwardly adjacent to the second sonar image slice; and

cause the composite down facing sonar image to be displayed on the user interface.

2. The apparatus of claim 1 , wherein generating the composite down facing sonar image comprises generating the composite down facing sonar image based on maximum intensity value sonar returns from among the first side facing sonar returns and the second side facing sonar returns, wherein a first sonar return from the first side facing sonar returns is selected for use in generating the composite down facing sonar image over a second sonar return from the second side facing sonar returns when the first sonar return would have a same position as the second sonar return within the composite down facing sonar image and has a greater intensity value than the second sonar return.

3. The apparatus of claim 1 , wherein generating the composite down facing sonar image comprises generating the composite down facing sonar image based on minimum intensity value sonar returns from among the first side facing sonar returns and the second side facing sonar returns, wherein a first sonar return from the first side facing sonar returns is selected for use in generating the composite down facing sonar image over a second sonar return from the second side facing sonar returns when the first sonar return would have a same position as the second sonar return within the composite down facing sonar image and has a lesser intensity value than the second sonar return.

4. The apparatus of claim 1 , wherein generating the composite down facing sonar image comprises generating the first sonar image slice based on a composite of weighted intensity values of the first side facing sonar returns and the second side facing sonar returns.

5. The apparatus of claim 1 , wherein the memory and the computer program code are further configured to, with the processor, cause the apparatus to:

receive down facing sonar returns from an underwater environment relative to a bottom of a vessel.

6. The apparatus of claim 5 , wherein the memory and the computer program code are further configured to, with the processor, cause the apparatus to:

generate a down sonar image based on the down facing sonar returns; and

cause the down sonar image to be displayed on the user interface,

wherein the composite down facing sonar image is displayed on the user interface in response to the down sonar image being unavailable.

7. The apparatus of claim 5 , wherein the composite down facing sonar image is further based on the down facing sonar returns.

8. A method of providing marine information, the method comprising:

receiving first side facing sonar returns from at least one first side facing transducer received from an underwater environment relative to a first side of a vessel;

receiving second side facing sonar returns from at least one second side facing transducer received from the underwater environment relative to a second side of the vessel, wherein the second side of the vessel is opposite the first side of the vessel;

generating a composite down facing sonar image formed based on historical one-dimensional sonar data taken over time from both of the first side facing sonar returns and the second side facing returns, wherein the down facing sonar image is formed of at least:

a first sonar image slice that is generated based on a composite of the first side facing sonar returns and the second side facing sonar returns taken at a first time; and

a second sonar image slice that is generated based on a composite of the first side facing sonar returns and the second side facing sonar returns taken at a second time, where the second time is different than the first time, wherein the down facing sonar image is built up of at least the first sonar image slice extending downwardly adjacent to the second sonar image slice; and

causing the composite down facing sonar image to be displayed on the user interface.

9. The method of claim 8 , wherein generating the composite down facing sonar image comprises generating the composite down facing sonar image based on maximum intensity value sonar returns from among the first side facing sonar returns and the second side facing sonar returns, wherein a first sonar return from the first side facing sonar returns is selected for use in generating the composite down facing sonar image over a second sonar return from the second side facing sonar returns when the first sonar return would have a same position as the second sonar return within the composite down facing sonar image and has a greater intensity value than the second sonar return.

10. The method of claim 8 , wherein generating the composite down facing sonar image comprises generating the composite down facing sonar image based on minimum intensity value sonar returns from among the first side facing sonar returns and the second side facing sonar returns, wherein a first sonar return from the first side facing sonar returns is selected for use in generating the composite down facing sonar image over a second sonar return from the second side facing sonar returns when the first sonar return would have a same position as the second sonar return within the composite down facing sonar image and has a lesser intensity value than the second sonar return.

11. The method of claim 8 , wherein generating the composite down facing sonar image comprises generating the first sonar image slice based on a composite of weighted intensity values of the first side facing sonar returns and the second side facing sonar returns.

12. The method of claim 8 further comprising:

receiving down facing sonar returns from an underwater environment relative to a bottom of a vessel.

13. The method of claim 12 further comprising:

generating a down sonar image based on the down facing sonar returns; and

causing the down sonar image to be displayed on the user interface,

wherein the composite down facing sonar image is displayed on the user interface in response to the down sonar image being unavailable.

14. The method of claim 12 , wherein the composite down facing sonar image is further based on the down facing sonar returns.

15. A system for providing marine information, the system comprising:

a plurality of sonar transducers, wherein each of the plurality of sonar transducers is configured to transmit one or more sonar beams into an underwater environment, wherein the plurality of sonar transducers comprises a first side facing transducer and a second side facing transducer; and

a marine electronic device comprising:

a user interface;

a processor;

a memory including computer program code, the memory and the computer program code configured to, with the processor, cause the apparatus to:

receive, from the first side facing transducer, first side facing sonar returns from the underwater environment relative to a first side of a vessel;

receive, from the second side facing transducer, second side facing sonar returns from the underwater environment relative to a second side of the vessel, which is opposite the first side of the vessel;

generate a composite down facing sonar image formed based on historical one-dimensional sonar data taken over time from both a composite of the first side facing sonar returns and the second side facing returns, wherein the down facing sonar image is formed of at least:

a first sonar image slice that is generated based on a composite of the first side facing sonar returns and the second side facing sonar returns taken at a first time; and

a second sonar image slice that is generated based on a composite of the first side facing sonar returns and the second side facing sonar returns taken at a second time, where the second time is different than the first time, wherein the down facing sonar image is built up of at least the first sonar image slice extending downwardly adjacent to the second sonar image slice;

cause the composite down facing sonar image to be displayed on the user interface.

16. The system of claim 15 , wherein generating the composite down facing sonar image comprises generating the composite down facing sonar image based on maximum intensity value sonar returns from among the first side facing sonar returns and the second side facing sonar returns, wherein a first sonar return from the first side facing sonar returns is selected for use in generating the composite down facing sonar image over a second sonar return from the second side facing sonar returns when the first sonar return would have a same position as the second sonar return within the composite down facing sonar image and has a greater intensity value than the second sonar return.

17. The system of claim 15 , wherein generating the composite down facing sonar image comprises generating the composite down facing sonar image based on minimum intensity value sonar returns from among the first side facing sonar returns and the second side facing sonar returns, wherein a first sonar return from the first side facing sonar returns is selected for use in generating the composite down facing sonar image over a second sonar return from the second side facing sonar returns when the first sonar return would have a same position as the second sonar return within the composite down facing sonar image and has a lesser intensity value than the second sonar return.

18. The system of claim 15 , wherein generating the composite down facing sonar image comprises generating the first sonar image slice based on a composite of weighted intensity values of the first side facing sonar returns and the second side facing sonar returns.

19. The system of claim 15 , wherein the memory and the computer program code are further configured to, with the processor, cause the apparatus to:

receive, from a down facing transducer, down facing sonar returns from the underwater environment relative to a bottom of a vessel;

generate a down sonar image based on the down facing sonar returns; and

cause the down sonar image to be displayed on the user interface,

wherein the composite down facing sonar image is displayed on the user interface in response to the down sonar image being unavailable.

20. The system of claim 15 , wherein the memory and the computer program code are further configured to, with the processor, cause the apparatus to:

receive, from a down facing transducer, down facing sonar returns from the underwater environment relative to a bottom of a vessel, wherein the composite down facing sonar image is further based on the down facing sonar returns.