Coherent Sonar Image Correlation via Grazing Angle Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Coherent sonar image correlation is challenging due to lack of frequency and aspect overlap, as well as sonar artifacts, making it difficult to achieve correlation between images of the same terrain observed from different angles.
Innovation Solution
The method involves forming sonar images using the open/closed aperture theorem, grazing angle compensation, and aspect compensation to align and correlate images, using overlapping frequencies and aspects, and calculating correlation coefficients to obtain a correlation image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If sonar images are observed from different angles to increase coverage, then the observation coverage is improved, but the correlation between images deteriorates due to lack of aspect overlap
Solution Approach 1:
The patent transforms the 2D sonar images into a common 3D coordinate system by introducing vertical dimension compensation through grazing angle correction. This allows images taken from different aspects to be correlated by projecting them onto a unified spatial framework, effectively resolving the aspect overlap problem while maintaining correlation capability.
Solution Approach 2:
The patent applies grazing angle compensation to transform the frequency parameters of sonar images. By correcting the frequency scaling effects caused by different grazing angles, the patent enables images observed from different angles to be correlated through parameter transformation, thus maintaining correlation while expanding observation coverage.
2Reliability
If grazing angle compensation is applied to enable correlation, then the image correlation is improved, but the processing complexity increases
Solution Approach 1:
The patent replaces complex mechanical array configurations with signal processing-based grazing angle compensation. Instead of requiring physically complex planar arrays to achieve angle-invariant imaging, the patent uses mathematical transformations on the received signals to achieve the same correlation effect, thereby reducing system complexity.
3Reliability
If frequency overlap is required for correlation, then the correlation capability is improved, but the adaptability to different observation conditions deteriorates
Solution Approach 1:
The patent uses grazing angle compensation to transform frequency parameters, allowing correlation between images with different frequency characteristics. By correcting the frequency scaling effects, the patent enables adaptability to different observation conditions while maintaining correlation capability through parameter transformation rather than requiring strict frequency overlap.
Data Source
AI summary
Systems and methods for coherent image correlation are provided. The systems include sonars with overlapping frequencies that observe terrain from overlapping aspects to form sonar images. First and second sonar images are formed and are grazing angle compensated. The first image is formed using the open or closed aperture theorem. Forming the second image using the open or closed aperture theorem constraint is optional. If the first and second images are not aligned, a range of possible rotations can be defined and image pairs can be created for a sampling of rotational angles. In addition, the images can be aspect compensated to remove windowing and beam pattern effects, if necessary. Once both images are grazing angle compensated and aligned, values are calculated for each possible image shift. To obtain a correlation image, the correlation coefficient for each possible image shift is calculated.