Holographic Map for Sonar Data Compression
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Solution Overview
Problem
Traditional maps fail to effectively describe underwater scenes using sonar data due to the dramatic change in observed phenomena with position and angle, requiring a four-dimensional representation that is cumbersome and inefficient for storage and correlation.
Innovation Solution
A holographic map that codes frequency and aspect information into two dimensions, utilizing the open/closed aperture theorem and grazing angle compensation to create spatially invariant images suitable for coherent correlation, reducing storage requirements and enabling efficient terrain recognition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a four-dimensional representation I(x,y,f,θ) is used to describe sonar scenes, then the representation captures frequency and aspect information accurately, but the storage requirements and complexity increase significantly
Solution Approach 1:
The patent applies holographic transformation to convert the four-dimensional representation I(x,y,f,θ) into a two-dimensional holographic map. This dimensional reduction is achieved by encoding frequency and aspect information into the spatial frequency domain of the hologram, allowing accurate representation while dramatically reducing storage requirements compared to direct four-dimensional storage.
2Adaptability or versatility
If traditional feature-based maps are used, then object locations can be represented, but the maps break down when using sonar images due to dramatic changes with position and angle
Solution Approach 1:
The patent transforms the representation from traditional Cartesian coordinates (x,y) to holographic coordinates that encode frequency and aspect information. This parameter transformation allows the map to adapt to sonar data characteristics, where the holographic representation maintains reliability across different positions and angles by capturing the essential spectral and directional information in a position-invariant manner.
3Device complexity
If contour or field maps are used to relate intensity to position, then the representation is simple, but it fails to capture the complex frequency and aspect dependence of sonar observations
Solution Approach 1:
The patent uses holographic transformation to encode frequency and aspect information into the spatial frequency domain. This allows the map to maintain relative simplicity while capturing complex sonar characteristics, as the hologram compresses the four-dimensional information into a two-dimensional structure that preserves essential spectral and directional data through its frequency content.
Data Source
AI summary
A holographic map is formed of one or more holograms or images conforming to the open/closed aperture theorem and grazing angle compensated. A hologram can be thought of as the sum of all images over a range of angles, wherein the frequency and aspect information is coded into two dimensions. An open/closed aperture image is an image having all points in the image observed over the same range of angles. Grazing angle compensation projects the data onto a representation of the sea floor and the image is rescaled by the cosine (or secant) of the angle between a ray connecting the sonar to a point on the sea floor. A valid range of viewing aspects is defined. The images in the holographic map have both a frequency band and range of aspects that, after grazing angle compensation, describe all locations in the map.