Claims:1. A system (100) for synthesizing reflection data for an active side scan sonar, said system comprising:
a computing device (102) adapted to receive one or more images pertaining to seafloor image, the one or more images are based on first set of parameters, said first set of parameters pertaining to any or a combination of reference image, maximum achievable swath range, operating frequency, operating bandwidth, pulse modulation, pulse time period, sampling frequency, speed of sound, resolution along track, resolution across track, altitude of system from seabed, and transducer depression angle; and
a processor (104) operatively coupled to the computing device, the processor configured to:
receive, from the computing device, the one or more images; and
synthesize the received one or more images based on second set of parameters, wherein, said second set of parameters pertaining to any or a combination of modified Lambertian reflectance data, anamorphic distortion, incorporation of nadir gap, and creation of granular speckle noise.

2. The system as claimed in claim 1, wherein the processor (104) creates simplified Lambertian reflectance data, wherein intensity parameter of said reflectance data is implemented using curve interpolation and curve fitting of any or a combination of frequency, salinity, depth, and temperature curves for predefined frequency range.
3. The system as claimed in claim 2, wherein the 4-degree polynomial equation generation for said reflectance data over predefined frequency range is implemented using curve interpolation and curve fitting, wherein normalization implemented for the parameter of the reflectance data to reduce scaling effects.
4. The system as claimed in claim 2, wherein the reflectance parameter of each point target is acquired from pixelated value of seafloor terrain containing mine like objects with shadow.
5. The system as claimed in claim 1, wherein the processor generates anamorphic distortion comprising any or a combination of across track resolution and along track resolution, wherein along track beam spread generated to estimate number of pixels to be averaged for along-track resolution variation implementation along range.
6. The system as claimed in claim 5, wherein across track curve generated and approximated using angular dependency of across track resolution based on bandwidth and operating frequency of transmit pulse, wherein change of order is implemented in case of reflectance and anamorphic distortion.
7. The system as claimed in claim 1, wherein the processor (104) creates nadir zone for side scan sonar.
8. The system as claimed in claim 7, wherein the processor (104) synthesizes nadir gap based on a trigonometric relation of beam width and depression angle.
9. The system as claimed in claim 1, the processor (104) creates granular speckle noise using any or a combination of random noise pattern with respect to randomize parameter and salt and pepper noise with respect to a defined probability parameter.
10. A method (700) for synthesizing reflection data for an active side scan sonar, said method comprising:
receiving (702), at a computing device, the one or more images pertaining to seafloor image, the one or more images are based on first set of parameters, said first set of parameters pertaining to any or a combination of reference image, maximum achievable swath range, operating frequency, operating bandwidth, pulse modulation, pulse time period, sampling frequency, speed of sound, resolution along track, resolution across track, altitude of system from seabed, and transducer depression angle; and
synthesizing (704), at the computing device, the received one or more images, based on second set of parameters, wherein said second set of parameters pertaining to any or a combination of modified Lambertian reflectance data, anamorphic distortion, incorporation of nadir gap, and creation of granular speckle noise.
, Description:TECHNICAL FIELD
[0001] The present disclosure relates, in general, to side scan sonar systems, and more specifically, relates to a system and method for underwater acoustic reflectance model generation incorporating distortion effects for side scan sonar (SSS) signal simulator.

BACKGROUND
[0002] Sonar system is an apparatus for estimating a direction and a range of an underwater target by using sound waves. Active side scan sonar systems are a category of sonar system to map the topography of the underwater seabed. Side scan sonar provided in different ways and with different levels of resolution. These side scan sonar systems provide very detailed images of the ocean floor.
[0003] Few exemplary existing technologies in the field of side scan sonar generate reflectance models that predominantly use hardware-based models with fewer model parameters. However, these existing technologies suffer from the limitations of creating a less realistic sonar data at the cost of complex high-end hardware.
[0004] Therefore, there is a need in the art to provide a means that generates underwater acoustic reflection incorporating distortion effects for side scan sonar without the use of any application-specific hardware, and thereby reduces the cost required for complex high-end hardware.

OBJECTS OF THE PRESENT DISCLOSURE
[0005] An object of the present disclosure relates, in general, to side scan sonar systems, and more specifically, relates to a system and method for underwater acoustic reflectance model generation incorporating distortion effects for side scan sonar (SSS) signal simulator.
[0006] Another object of the present disclosure is to provide a system that simulates signals specialized for side scan sonar in active mode of operation.
[0007] Another object of the present disclosure is to provide a system that generates reflectance model for a moving side scan system incorporating both geometric and radiometric distortion effects.
[0008] Another object of the present disclosure is to provide a system that generates realistic sonar data effectively.
[0009] Another object of the present disclosure is to provide a system that reduces the cost required for complex high-end hardware.
[0010] Yet another object of the present disclosure is to provide a system that uses a simulator device to generate real time signals for side scan sonar without the use of any application specific hardware.

SUMMARY
[0011] The present disclosure relates, in general, to side scan sonar systems, and more specifically, relates to a system and method for underwater acoustic reflectance model generation incorporating distortion effects for side scan sonar (SSS) signal simulator.
[0012] The present disclosure is related to modelling underwater acoustic reflection incorporating distortion effects for the active side scan sonar system. The present disclosure simulates signals specialized for side scan sonar in an active mode of operation and used in a simulator device to generate real-time signals for side scan sonar without the use of any application-specific hardware. The present disclosure generates a reflectance model for a moving side scan system incorporating both geometric and radiometric distortion effects. The methodology consists of the reflectance model based on modified Lambertian reflectance equation, geometric distortion model generating anamorphic distortion effects, nadir gap synthesizer and radiometric distortion model generating speckle noise. The engine can be implemented on any hardware irrespective of their architecture.
[0013] The present disclosure generates the underwater acoustic reflectance model incorporating distortion effects for the active side scan sonar signal based on reference seafloor image. A simplified but accurate modified Lambertian model used for reflection modelling. Geometric distortion model generates an accurate reflected signal incorporating anamorphic effects. Nadir region model implements near region resolution variation effect. Radiometric distortion model generates speckle noise type based on a novel noise generation algorithm.
[0014] In an aspect, the present disclosure provides a system for synthesizing reflection data for an active side scan sonar, the system including a computing device adapted to receive one or more images pertaining to seafloor image, the one or more images are based on first set of parameters, the first set of parameters pertaining to any or a combination of reference image, maximum achievable swath range, operating frequency, operating bandwidth, pulse modulation, pulse time period, sampling frequency, speed of sound, resolution along track, resolution across track, altitude of system from seabed, and transducer depression angle and a processor operatively coupled to the computing device, the processor configured to receive, from the computing device, the one or more images, and synthesize the received one or more images based on second set of parameters, wherein, the second set of parameters pertaining to any or a combination of modified Lambertian reflectance data, anamorphic distortion, incorporation of nadir gap, and creation of granular speckle noise.
[0015] In an embodiment, the processor may create simplified Lambertian reflectance data, wherein intensity parameter of the reflectance data is implemented using curve interpolation and curve fitting of any or a combination of frequency, salinity, depth, and temperature curves for predefined frequency range.
[0016] In another embodiment, the 4-degree polynomial equation generation for the reflectance data over predefined frequency range is implemented using curve interpolation and curve fitting, wherein normalization implemented for the parameter of reflectance data to reduce scaling effects.
[0017] In another embodiment, the reflectance parameter of each point target may be acquired from pixelated value of seafloor terrain containing mine like objects with shadow.
[0018] In another embodiment, the processor may generate anamorphic distortion including any or a combination of across track resolution and along track resolution, wherein along track beam spread generated to estimate number of pixels to be averaged for along-track resolution variation implementation along range.
[0019] In another embodiment, the across track curve generated and approximated using angular dependency of across track resolution based on bandwidth and operating frequency of transmit pulse, wherein change of order is implemented in case of reflectance and anamorphic distortion.
[0020] In another embodiment, the processor may create nadir zone for side scan sonar.
[0021] In another embodiment, the processor may synthesize nadir gap based on a trigonometric relation of beam width and depression angle.
[0022] In another embodiment, the processor may create granular speckle noise using any or a combination of random noise pattern with respect to randomize parameter and salt and pepper noise with respect to a defined probability parameter.
[0023] In an aspect, the present disclosure provides a method for synthesizing reflection data for an active side scan sonar, the method includes receiving, at a computing device, the one or more images pertaining to seafloor image, the one or more images are based on first set of parameters, the first set of parameters pertaining to any or a combination of reference image, maximum achievable swath range, operating frequency, operating bandwidth, pulse modulation, pulse time period, sampling frequency, speed of sound, resolution along track, resolution across track, altitude of system from seabed, and transducer depression angle; and synthesizing, at the computing device, the received one or more images, based on second set of parameters, wherein the second set of parameters pertaining to any or a combination of modified Lambertian reflectance data, anamorphic distortion, incorporation of nadir gap, and creation of granular speckle noise.
[0024] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0026] FIG. 1A illustrates an exemplary functional component of a system, in accordance with an embodiment of the present disclosure.
[0027] FIG. 1B illustrates an exemplary view of the system for synthesizing reflection data for an active side scan sonar, in accordance with an embodiment of the present disclosure.
[0028] FIG. 2 illustrates an exemplary view of modified Lambertian model, in accordance with an embodiment of the present disclosure.
[0029] FIG. 3 illustrates an exemplary view of modified Lambertian model with equation, in accordance with embodiments of the present disclosure.
[0030] FIG. 4 illustrates an exemplary view of anamorphic distortion, in accordance with embodiments of the present disclosure
[0031] FIG. 5 illustrates an exemplary view of nadir region, in accordance with embodiments of the present disclosure.
[0032] FIG. 6 illustrates an exemplary view of speckle noise, in accordance with embodiments of the present disclosure.
[0033] FIG. 7 illustrates an exemplary flow diagram of a method for synthesizing reflection for an active side scan sonar, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0034] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0035] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0036] The present disclosure relates, in general, to side scan sonar systems, and more specifically, relates to a system and method for underwater acoustic reflectance model generation incorporating distortion effects for side scan sonar (SSS) signal simulator.
[0037] The present disclosure is related to modelling underwater acoustic reflection incorporating distortion effects for the active side scan sonar system. The present disclosure simulates signals specialized for side scan sonar in an active mode of operation and used in a simulator device to generate real-time signals for side scan sonar without the use of any application-specific hardware. The present disclosure generates a reflectance model for a moving side scan system incorporating both geometric and radiometric distortion effects. The methodology consists of the reflectance model based on modified Lambertian reflectance equation, geometric distortion model generating anamorphic distortion effects, nadir gap synthesizer and radiometric distortion model generating speckle noise. The engine can be implemented on any hardware irrespective of their architecture.
[0038] The present disclosure generates the underwater acoustic reflectance model incorporating distortion effects for the active side scan sonar signal based on reference seafloor image. A simplified but accurate modified Lambertian model used for reflection modelling. Geometric distortion model generates an accurate reflected signal incorporating anamorphic effects. Nadir region model implements near region resolution variation effect. Radiometric distortion model generates speckle noise type based on a novel noise generation algorithm. The present disclosure can be described in enabling detail in the following examples, which may represent more than one embodiment of the present disclosure.
[0039] FIG. 1A illustrates an exemplary functional component of a system, in accordance with an embodiment of the present disclosure.
[0040] Referring to FIG. 1A, systems 100 configured to generate underwater acoustic reflectance model also interchangeably referred to as reflectance data for side scan sonar system. The system 100 may include a single board computer (SBC) 102 also interchangeably referred to as a computing device 102. The SBC 102 may include processor 104 also interchangeably referred to as engine 104, monitor/keyboard 106, a display 108 and power supply card 110. Side scan sonar is a category of sonar system to map topography of underwater seabed. It uses a device that emits conical fan shaped acoustic pulse over a swath and intensity of reflected signal is captured, sampled and mapped onto a series of across-track slices. The present disclosure generates the dataset for simulated transmit and receive signals, underwater environment and electronics in spatio-temporal domain.
[0041] In an embodiment, the system 100 may generate the underwater acoustic reflectance model incorporating distortion effects for the active side scan sonar signal based on reference seafloor image. A simplified but accurate modified Lambertian model used for reflection modelling. Geometric distortion model may generate an accurate reflected signal incorporating anamorphic effects. Nadir region model may implement near region resolution variation effect, and radiometric distortion model may generate speckle noise type based on a novel noise generation algorithm.
[0042] In an exemplary embodiment, the system 100 as presented in the example may be implemented in the seafloor survey. As can be appreciated, the present disclosure may not be limited to this configuration but may be extended to other configurations such as mine detection, and recreational pursuits such as fishing and the like.
[0043] FIG. 1B illustrates an exemplary view of the system for synthesizing reflection data for the active side scan sonar, in accordance with an embodiment of the present disclosure. The computing device 102 adapted to receive one or more images pertaining to seafloor image, the one or more images may be based on first set of parameters also interchangeably referred to as input parameters, where the input parameters may include any or a combination of reference image containing mine like objects IMmn, maximum achievable swath range Ls, operating frequency Fc, operating bandwidth Bw, pulse modulation Pm, pulse time period Tp, sampling frequency Fs, speed of sound Vc, resolution along track Ral, resolution across track Rac, altitude of system from seabed h, and transducer depression angle Da.
[0044] In another embodiment, the processor 104 operatively coupled to the computing device 102, the processor 104 configured to receive, the one or more images. The processor 104 configured to synthesize the received one or more images based on second set of parameters. The second set of parameters also interchangeably referred to as output parameters, where the output parameters may include any or a combination of reflectance model IMlb also interchangeably referred to as modified Lambertian reflectance data, anamorphic distortion model IMam, nadir gap model IMnr and speckle noise model IMsp. In other words, the synthesis of reflection data may include any or a combination of modified Lambertian model synthesis, geometric distortion model incorporating anamorphic distortion effects, nadir region generation, and radiometric distortion model consist of speckle noise model synthesis, which are explained in detail below.
[0045] For example, the seafloor reference image IMmn is fed into the system that may include the computing device, the processor configured to synthesize the seafloor reference image using any or a combination of modified Lambertian model synthesis, geometric distortion model incorporating anamorphic distortion effects, nadir region generation, and radiometric distortion model consist of speckle noise model synthesis.
[0046] In an embodiment, the processor 104 may synthesize active side scan sonar reflectance model based on modified Lambertian equation incorporating underwater distortion effects. The processor 104 may synthesize the simple reflectance model and generate IMlb from IMmn. The processor 104 may synthesize the simple and accurate reflection model using modified Lambertian model based on operating frequency, salinity, depth, temperature, object/surface reflectance, incident angle, and position for two-way propagation, from a point source to a point target and back and incorporate the same in the generated model.
[0047] In another embodiment, the processor 104 may synthesize reflection model with least error for the frequency range of around100Hz to 1MHz and incorporate the same in the generated model. The processor 104 may synthesize reflection model for frequencies less than 100Hz and greater than 1MHz with improved error ratio using six-degree polynomial equation generated using curve interpolation and curve fitting technique and incorporate the same in the generated model.
[0048] In another embodiment, the processor 104 may synthesize anamorphic distortion using the multi-resolution topology in the spatio-temporal domain and incorporate the same in the generated model. The processor 104 may synthesize the anamorphic distortion model and may generate IMam from IMlb. In another embodiment, the processor 104 may synthesize water column offset or altitude-based nadir gap, and incorporate the same in the generated model, where the processor 104 may synthesize nadir gap and may incorporate the same in IMam generating IMnr.
[0049] In another embodiment, the processor 104 may synthesize random granular speckle noise model based on different underwater conditions and a simplified Rayleigh multiplicative model and incorporate the same in the generated model, where the processor 104 may synthesize speckle noise model and may generate IMsp from IMnr.
[0050] In another exemplary embodiment, the system 100 may include the SBC 102 with input/output IO devices like keyboard/mouse 106 and monitor 108, where the above-described process may be implemented to generate the active side scan reflectance data. The system 100 can be realized on any hardware irrespective of their architecture. In an exemplary embodiment, a single-core processor-based board having a base frequency of 1GHz may be used for system implementation. The system 100 can be realized on any hardware irrespective of their architecture. Minimum processor features required depends on the end-user application.
[0051] Thus, the system 100 may simulate signals specialized for side scan sonar in the active mode of operation and use simulator device configured to generate real-time signals for side scan sonar without the use of any application-specific hardware. The system 100 generates the reflectance model for the moving side scan system incorporating both geometric and radiometric distortion effects. The present disclosure generates realistic sonar data effectively, and further, reduces the cost required for complex high-end hardware.
[0052] FIG. 2 illustrates an exemplary view of modified Lambertian model 200, in accordance with an embodiment of the present disclosure.
[0053] Referring to FIG. 2, the engine 104 may synthesize active side scan sonar reflectance model based on modified Lambertian equation incorporating underwater distortion effects using the algorithms as described in FIG. 1B. The engine 104 may synthesize the simple and accurate reflection model using modified Lambertian model based on operating frequency, salinity, depth, temperature, object/surface reflectance, incident angle, and position for two-way propagation, from the point source to the point target and back and incorporate the same in the generated model.
[0054] The engine 104 may compute 4-degree polynomial equation generation for the reflectance data over predefined frequency range implemented using curve interpolation and curve fitting, where normalization implemented for the parameter of reflectance data to reduce scaling effects. The reflectance parameter of each point target may be acquired from pixelated value of seafloor terrain containing mine like objects with shadow.
[0055] In an exemplary embodiment, the engine 104 may synthesize reflection model, with least error for the frequency range of 100Hz to 1MHz and incorporate the same in the generated model. The engine 104 may synthesize the simple reflectance model based on equation shown in FIG. 2 as described below and generate reflectance model IMlb from IMmn. The equation used is modified Lambertian model by giving the normalization factor for individual parameters and incorporating intensity parameter in terms of frequency, salinity, depth, and temperature. This model does not use any sensitivity pattern models based on equations containing complex functions like Bessel functions. The model gives reflected intensity based on propagation loss, object reflectivity, and angle of incidence for a wide frequency range of 100Hz to 1MHz within an error factor of 10%. The model considers the incidence angle with respect to a perpendicular to the ground implementing a simple design. Parameter r, in Lambertian equation, is the slant distance calculated using the equation below,

where x is the distance on floor with respect to the perpendicular made by h. Factor 2 in above equation is due to the to and fro distance due to active sonar operation. FIG. 2 shows incident angle In, near nadir Ln and incident angle Is at maximum achievable swath, Ls.
[0056] FIG. 3 illustrates an exemplary view of modified Lambertian model with equation 300, in accordance with embodiments of the present disclosure.
[0057] Referring to FIG. 3, the engine 104 may synthesize reflection model for frequencies less than 100Hz and greater than 1MHz with improved error ratio using six-degree polynomial equation generated using curve interpolation and curve fitting technique and incorporate the same in the generated model. FIG. 3 illustrates the range vs intensity plot for the modified Lambertian model with the equation. The model incorporates a 4-degree polynomial equation shown below, for frequency range beyond 100Hz to 1MHz using curve interpolation and curve fitting technique. The equation for modified Lambertian model is given below, where r is the range of operation for 35 ppt salinity, 10o temperature, pH 8, unity object reflectivity, and 100KHz frequency.

Similar way, for different conditions, model based on modified equation can be generated in terms of range.
[0058] FIG. 4 illustrates an exemplary view of anamorphic distortion 400, in accordance with embodiments of the present disclosure. As shown in FIG. 4, the engine 104 may synthesize anamorphic distortion, using the multi-resolution topology in the spatio-temporal domain and incorporate the same in the generated model. The engine 104 may synthesize the anamorphic distortion model and may generate anamorphic distortion model IMam from IMlb.
[0059] The engine 104 may generate anamorphic distortion including any or a combination of across track resolution and along track resolution, where along track beam spread generated to estimate number of pixels to be averaged for along-track resolution variation implementation along range. The across track curve generated and approximated using angular dependency of across track resolution based on bandwidth and operating frequency of transmit pulse, where change of order of algorithm is implemented in case of reflectance and anamorphic distortion. FIG. 4 shows the relation of across track and along track spreading due to transducer beam-width as well as range.
[0060] Equation below shows the estimated number of pixels to be averaged for along track resolution distortion.

[0061] Along track spread at range R1 is lesser than spread at range R2 and it is lesser compared at range R3.
[0062] Equation below shows the estimated number of pixels to be averaged for across track resolution distortion.

[0063] Across track spread at range R3 is lesser than spread at range R2 and it is lesser compared at range R1. For simplicity, in this model arc length is approximated as linear pixels in along track spreading calculation. Also, both spread parameters are rounded to nearest integer for making side scan algorithm less complex.
[0064] FIG. 5 illustrates an exemplary view of nadir region 500, in accordance with embodiments of the present disclosure.
[0065] Referring to FIG. 5, the engine 104 may synthesize water column offset or altitude-based nadir gap, and incorporate the same in the generated model. The engine 104 may create nadir zone for side scan sonar and may synthesize nadir gap based on a trigonometric relation of beam width and depression angle. As shown in FIG. 5, engine 104 synthesizes nadir gap and incorporates the same in anamorphic distortion model IMam generating IMnr. FIG. 5 shows nadir gap Ln and it is estimated as

where Depression angle Da, has significant effect on Ln and Ls
[0066] FIG. 6 illustrates an exemplary view of speckle noise 600, in accordance with embodiments of the present disclosure. As shown in FIG. 6, the engine 104 may synthesize random granular speckle noise model based on different underwater conditions and the simplified Rayleigh multiplicative model and incorporates the same in the generated model. The engine 104 may create granular speckle noise using any or a combination of random noise pattern with respect to randomize parameter and salt and pepper noise with respect to a defined probability parameter.
[0067] As shown in FIG. 6, the engine 104 synthesizes speckle noise model and generates speckle noise model IMsp from IMnr. Speckle model may be generated as any or a combination of random generator function and salt and pepper noise function producing granular random noise effect, given as IMsp = IMnr + (noise *IMnr).
[0068] FIG. 7 illustrates an exemplary flow diagram of a method for synthesizing reflection data for an active side scan sonar, in accordance with an embodiment of the present disclosure.
[0069] The method 700 can be implemented using a computing device, which can include one or more processors. At block 702, receive, from the computing device, the one or more images pertaining to seafloor image, the one or more images are based on first set of parameters, the first set of parameters pertaining to any or a combination of reference image, maximum achievable swath range, operating frequency, operating bandwidth, pulse modulation, pulse time period, sampling frequency, speed of sound, resolution along track, resolution across track, altitude of system from seabed, and transducer depression angle.
[0070] At block 704, the computing device synthesize the received one or more images based on second set of parameters, where the second set of parameters pertaining to any or a combination of modified Lambertian reflectance data, anamorphic distortion, incorporation of nadir gap, and creation of granular speckle noise.
[0071] It will be apparent to those skilled in the art that the system 100 of the disclosure may be provided using some or all of the mentioned features and components without departing from the scope of the present disclosure. While various embodiments of the present disclosure have been illustrated and described herein, it will be clear that the disclosure is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the disclosure, as described in the claims.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0072] The present disclosure provides a system that simulates signals specialized for side scan sonar in active mode of operation.
[0073] The present disclosure provides a system that generates reflectance model for a moving side scan system incorporating both geometric and radiometric distortion effects.
[0074] The present disclosure provides a system that generates realistic sonar data effectively.
[0075] The present disclosure provides a system that reduces the cost required for complex high-end hardware.
[0076] The present disclosure provides a system that uses a simulator device to generate real time signals for side scan sonar without the use of any application-specific hardware.