Position Correction Using Echoes From a Navigation Fix for Synthetic Aperture Sonar Imaging

被引:10
作者
Shippey, Geoffrey [1 ]
Jonsson, Mattias [2 ]
Pihl, Jorgen N. B. [2 ]
机构
[1] Chalmers Univ Technol, Dept Signals & Syst, SE-41296 Gothenburg, Sweden
[2] Swedish Def Res Agcy, SE-16490 Stockholm, Sweden
关键词
Autofocus; autopositioning; displaced phase center antenna (DPCA); micronavigation; shallow-water acoustics; synthetic aperture sonar (SAS); AUTOFOCUS;
D O I
10.1109/JOE.2009.2022578
中图分类号
TU [建筑科学];
学科分类号
0813 ;
摘要
In synthetic aperture sonar (SAS), the platform position must be known sufficiently accurately for signals to be added coherently along the synthetic aperture. Often, the onboard navigation system is insufficiently accurate by itself, so corrections are needed. A well-known method is the displaced phase center antenna (DPCA) procedure for correcting platform position using seabed echoes. DPCA methods have the advantage of insensitivity to changing interference patterns, moving specular reflection, and changing occlusion, with aspect. However, when seabed echoes are unusable, either because they are too weak, or because they are corrupted by multipath, the seabed DCPA method may fail. Therefore, we present an alternative DPCA method using sonar echoes from a suitable navigation fix, based on an object detected after standard beamforming. In our proposed system, look angle is obtained by tracking the centroid of the rectified image of the fix object. When the standard DPCA correction equations are modified for a fixed reflector, it turns out that they provide incremental range and look-angle errors, precisely the values required when the target itself is used as the navigation fix. Moreover, the values obtained are then self-compensating for errors in estimating seabed depth or forward motion of the platform. The navigation fix is selected by bracketing in range, and beamforming overlapping subsets of the receiver array. In this paper, we present experimental results at transmitter frequencies of 25 and 100 kHz where our method enabled well-focused SAS images to be generated with little recourse to other navigation information. Hence, SAS can be carried out, even when a sophisticated inertial navigation system (INS) is not available.
引用
收藏
页码:294 / 306
页数:13
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