ALYOTECH Technologies has been developing for few years a real-time simulator of the sea surface (SeaMotion). Our proposition now extends to subsea, thanks to our tool SIMSON, which simulates underwater acoustic propagation in sonar imagery.

Need

Sonar imagery is used in the military field, with searching mines for example, but also in the civil field searching for ship wrecks, and surveying of submerged structures… The SIMSON tool allows the interactive production of a wide variety of sonar images, enabling sonar operators to train in detection-recognition-identification of objects. Building a database of objects seen from different points of view can help in the development of new processes, such as the classification of objects or data fusion. As our tool uses the technical specifications of the sonar, SIMSON allows the evaluation of sensor performances.

Performance optimization

From a research software, developed in an interpreted language, that we have converted into C++ and optimized (memory optimization, CPU parallelization), we achieved a result which was 7.5 times faster than the initial program. The ray tracing implementation on graphical processor (GPU), provided by the OPTIX library of NVIDIA, allowed the speed to be increased by 40 times. The computation time has been reduced by a factor of 300 compared to the original version.

Technical innovation

The technical innovation provided by GPU implementation allows us to propose a scientific innovation with a more accurate acoustic propagation. The chosen method, based on ray tracing, has been extended with the multi-path (forward reflexion). These developments allowed the reproduction of ghost echoes visible in real images. The difficulty in underwater acoustic propagation lies also in the ray curvature, linked to oceanographic conditions. This bathycelerimetry phenomenon is included into calculations and has been validated by comparison with a reference program.

Definition of a scenario

SIMSON proposes a complete environment to define a scenario. An infinite seabed can be built, offering a variety of height maps, materials. This theatre is then completed with objects, whose position, attitude, dimensions, shrouding are customizable. Two types of sonar systems can be defined: side-scan and sector-scan. Systems are described with specific parameters and their path in the scene. Several modelling levels of the propagation are proposed, in order to quantify the impact of each in the final result: bathycelerimetry, directivity, transmission loss…Images are displayed as the calculation is running and a 3D viewer shows at the same time the sonar moving in the scene.

Financial support

SIMSON software has been developed by ALYOTECH Technologies within a Rapid project supported in part by the French MoD and in partnership with ENSTA-Bretagne.