Coherence Estimation for Repeat-Pass Interferometry


  1. Dillon, J.
  2. Myers, V.
Corporate Authors
Defence Research and Development Canada, Atlantic Research Centre, Halifax NS (CAN);Kraken Sonar Systems Inc., St. John's NL (CAN)
Coherently combining two or more Synthetic Aperture Sonar (SAS) images acquired at different times has two principal applications: Coherent Change Detection (CCD) [1] and high resolution bathymetry [2]. CCD is a promising technology for detecting changes when there is negligible variation in the mean backscattered energy by exploiting the phase of the sonar images; such changes could be caused by a new object present on the seafloor, by subtle changes in topography, or by a perturbation of the spatial distribution of the scatterers in a resolution cell. CCD can be used when the nature of the change is not known in advance, or as a data reduction or false alarm mitigation step by focusing attention on pixels in the sonar image where changes are likely to have occurred, particularly in areas of high clutter. Similarly, highly precise bathymetric maps can be produced by processing images obtained from repeated passes at different altitudes, creating a baseline that can be used to determine the topography of the seafloor. In order to apply repeat-pass techniques, pairs of images must be processed interferometrically, which places very stringent requirements on the acquisition geometry, navigational accuracy and stability of the environment. One must also coregister sonar images with sub-pixel accuracy. A corollary application of the coregistration step is the ability to produce a very accurate position correction for Autonomous Underwater Vehicles (AUVs) to help overcome the unav
synthetic aperture sonar
Report Number
DRDC-RDDC-2015-N021 — External Literature
Date of publication
29 Dec 2012
Number of Pages
Electronic Document(PDF)

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