SACLANT Undersea Res. Ctr., Viale San Bartolomeo 400, La Spezia 1938, Italy
The first successful demonstration of the feasibility of localizing a source in the ocean with matched-field processing was in the Arctic Ocean (Fizell and Wales). This environment/site was chosen because of the essential range independence of its sound-speed structure and minimal bottom reflectivity. Replica fields were generated with Kutschale's well-tested, precise but computationally exhaustive FFP code. Soon thereafter Porter demonstrated that the precision of his much faster normal mode code equaled FFP, permitting computations of large numbers of replica fields and rapid ``testing'' of numerous environmental hypotheses,'' i.e., matched-field inversion. The first inversions were of under-ice reflectivity and phase versus grazing angle (Livingston and Diachok). Other inversions through matched-field processing soon followed: ocean sound-speed profile (Kerengeleu and Diachok; and Goncharov and Voronovich), and bottom geoacoustic parameters (Fizell and Diachok; Chapman and McKirdy; and Collins, Kristensen et al.).