## Efficient image reconstruction techniques for a multiple-receiver synthetic aperture sonar (2001)

Citations: | 1 - 0 self |

### BibTeX

@TECHREPORT{Wilkinson01efficientimage,

author = {David R. Wilkinson and B. E. (hons},

title = {Efficient image reconstruction techniques for a multiple-receiver synthetic aperture sonar},

institution = {},

year = {2001}

}

### OpenURL

### Abstract

Christchurch, New Zealand. Fast and efficient imaging techniques have been developed for reconstructing data from the single-receiver synthetic aperture sonar (SAS). Therefore, it is advantageous to be able to combine multiple-receiver SAS data into the single-receiver data equivalent to employ these existing algorithms. In this thesis, a method is developed for combining the data efficiently. This method can be used with SAS systems containing any number of hydrophones arbitrarily located in a linear array and with the imaging platform travelling at any velocity. Motion errors resulting from the towed platform deviating from its straight path need to be determined and compensated accordingly. Sway and yaw are the primary motion errors of concern in low glancing angle side-looking sonar, since they are the major cause of image errors and artifacts in the reconstructions. Algorithms for es-timating both sway and yaw are presented based on prominent points. These have shown to work well in simulations.

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Citation Context ...ting image reconstruction algorithms are not lost. In this chapter an efficient and fast method is presented to combine data from any number of receivers with the platform travelling at any velocity [=-=Hayes and Gough 1999-=-]. 3.1 MULTIPLE-RECEIVER SAS MODEL The following sections describe the single-transmitter, multiple-receiver SAS model. Phase errors introduced by assumptions made in the SAS model are examined so the... |

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Citation Context ...tines typically compute two to three times faster than the equivalent Matlab routines. During the course of this thesis, two papers were written based on the algorithms developed in chapters 3 and 4 [=-=Gough et al. 2000-=-, Wilkinson et al. 2000]. 1.6 THESIS OUTLINE Chapter 2 presents the wavenumber algorithm, used as the algorithm of choice for reconstructing the SA data used throughout this thesis. The reconstructed ... |

2 |
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Citation Context ...pe of artifact is grating lobes. These occur in image space when the aperture is undersampled. Due to aliasing we get copies of the main lobe spaced evenly either side of the main lobe [Hawkins 1996, =-=Pat 2000-=-]. Two types of common image errors are defocusing, and speckle. Defocusing of objects in an image occurs when the actual and expected receiver’s along-track position differ. Variation in platform spe... |

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Citation Context ...85]. From its humble beginnings in the field of Synthetic Aperture Radar (SAR) [Cutrona et al. 1961, Sherwin et al. 1962], applications using the underwater equivalent Synthetic Aperture Sonar (SAS) [=-=Walsh 1969-=-] are now being explored. The desire for increased mapping rates lead to the development of a multiple-receiver SAS, introducing a new set of challenges to overcome. The chapter concludes with the con... |

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1 |
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Citation Context ...ed to slow forward velocities to prevent spatial undersampling along the aperture. Between transmitted pings, the platform can travel no further than half the linear extent of the largest transducer [=-=Rolt and Schmidt 1992-=-]. The other restricting factor is that the maximum unambiguous range is one-half the round trip distance travel in one pulse period. Thus, to improve the sampling rate either the pulse repetition rat... |

1 |
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Citation Context ...ibutions made and an outline of this thesis. 1.1 REAL VERSUS SYNTHETIC APERTURE IMAGING Initially, sonar and radar imaging was typically performed using a side-looking real aperture (antenna) system [=-=Somers and Stubbs 1984-=-]. With the imaging system travelling along a straight path, a pulse is periodically transmitted perpendicular to the direction of travel. This pulse is then reflected back by targets of interest to t... |

1 |
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Citation Context ...pute two to three times faster than the equivalent Matlab routines. During the course of this thesis, two papers were written based on the algorithms developed in chapters 3 and 4 [Gough et al. 2000, =-=Wilkinson et al. 2000-=-]. 1.6 THESIS OUTLINE Chapter 2 presents the wavenumber algorithm, used as the algorithm of choice for reconstructing the SA data used throughout this thesis. The reconstructed images often have artif... |