Micro-Navigation for Repeat-Pass Synthetic Aperture Sonar Interferometry
Abstract
AbstractSynthetic aperture sonar (SAS) is an underwater remote-sensing technology that can produce acoustic advanced processing of" the acoustic echo signals based on precise navigation of the sensor~s path through the water. The necessary precision is made possible using the technique of micro-navigation, which infers the navigation solution from information contained in the echo signals acquired at subsequent path positions.Repeat-pass SAS interferometry extends the SAS method by combining information across repeated passes. The established technique of coherent change detection uses the magnitude of the interference pattern between passes to measure sub-resolution changes in the seafloor.This is useful for detecting small disturbances, e.g., from natural or anthropogenic processes. Conventionally, interference patterns between repeated passes have been generated after warping the images from each pass onto a common coordinate frame. This has been effective for CCD. However, the warping process corrupts the phase information by confounding the three main factors that affect phase: 1) high-resolution bathymetry; 2) fluctuations in the medium; and 3) navigation errors. Instead, there is potential to exploit the phase information,by separating this triad of confounding factors. We expect this to lead to two new capabilities in seafloor imaging: ultra-high-resolution bathymetric mapping via repeated passes with a baseline separation; and bathymetric CCD by combining CCD with a repeat-pass baseline.Both methods are proven already in the closely related field of synthetic aperture radar.This project aims to improve and enhance repeat-pass SAS interferometry and, ultimately, to enable advanced methods for ultra-high-resolution bathymetric mapping and bathymetric CCD. To this end, our objective is to create new algorithms that generalise the micronavigation technique over repeated passes in place of (or to complement) image warping. In this way, we expect to accurately and precisely estimate repeat-pass navigation errors and work towards an online capability for correcting these errors. Moreover, we expect to be able to separate the confounding factors that influence repeat-pass phase measurements, there"by permitting the exploitation of useful information that is represented in the phase.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2019
- Source ID
- N000141912452
Entities
People
- Alan J. Hunter
Organizations
- Office of Naval Research
- United States Navy
- University of Bath