Comparative Analysis of Tomographic Methods for the Observation of Inhomogeneities in a Shallow Sea

Forward Scattering Observation With Partially Coherent Spatial Processing of Vertical Array Signals in Shallow Water

“…4(a) and (c) shows the cross sections (14) with respect to the inhomogeneity travel velocity (for and ) for both inhomogeneities, and Fig. 4(b) and (d) shows the cross sections (14) with respect to the inhomogeneity length (for and ). For the large inhomogeneity, the curves are smooth with a single well-defined peak, and the velocity and length estimates are, therefore, nonambiguous and accurate, i.e., they are very close to the true parameter values, thus providing experimental verification of the efficiency of matched filter processing (9).…”

“…Fig. 4(a) and (c) shows the cross sections (14) with respect to the inhomogeneity travel velocity (for and ) for both inhomogeneities, and Fig. 4(b) and (d) shows the cross sections (14) with respect to the inhomogeneity length (for and ).…”

“…The intersection time is determined by the location of the maximum of , while the cross-sectional area of the inhomogeneity normal to the acoustical path is estimated from the value of the maximum of by (13). To estimate the inhomogeneity velocity and length, SNR (14) was maximized with respect to each unknown parameter. Fig.…”

“…The peaks correspond to the times of acoustic path intersection by the inhomogeneities. Define the SNR as the ratio between an increment in the average value of the output process due to the presence of useful signal and the standard deviation of fluctuations in the absence of useful signal [21] SNR (14) where the notation implies taking the time average when the inhomogeneity is not present. In decibels…”

“…This processing yielded the best performance for detection and parameter estimation. A series of lake experiments was conducted in 1997-1999 and reported in [13] and [14]. They provided additional demonstrations of various receiving array geometries and signal processing algorithms for observing a moving inhomogeneity against the fluctuations of the strong direct signal.…”