Comparison between whitened generalized cross correlation and adaptive filter for time delay estimation with scattered arrays for passive positioning of moving targets in Baltic Sea shallow waters

Results from an acoustic measurement campaign in shallow waters (at 22 meters depth) are given. Eight hydrophones, placed at the seabed, were used simultaneously to investigate how different distances between hydrophones affect the Time Delay Estimation (IDE). In order to position targets two TDE methods were applied. The used methods were the Generalized Cross Correlation (GCQ function weighted by the Phase Transform (PHAT) and an adaptive Normalized Least Mean Square (NLMS) filter estimating the TDE between pairs of sensors. The two methods gave approximately the same result, except for the largest baseline where the GCC PHAT performed better. In the study we found that increasing separation distance decrease the bandwidth of coherence between the signals, however the study also indicated that scattered arrays with large baselines has better positioning capability than those with small baselines.