Multifrequency Biplanar Interferometric Imaging

The resolution of 3-D imaging is greatly improved using a new multifrequency biplanar interferometry (MBI) technique. Using data from a multifrequency-acoustic pulse-echo system, ranges to coherent targets, estimated from propagation delays, and the phase differences between echoes received with four quadrants of a split-aperture array are converted to Cartesian distances, and transformed into Earth coordinates. The collective data set is interpolated to create a surface closely approximating the target´s image. The resolution of the resulting image is improved orders of magnitude relative to those created with measures based on echo-intensity or single-frequency uniplanar interferometry. The effectiveness of MBI is demonstrated using data from a multifrequency (18 to 200 kHz) split-aperture echosounder system to produce composite high-resolution (submeter precision) images of the seabed sensed at long ranges (tens to hundreds of meters). MBI can be broadly applied to data from split-aperture remote-sensing systems which use acoustic or electromagnetic waves.