Synthetic aperture is a technique that enables high resolution sonar imagery through the coherent processing of consecutive displaced echo data. Instead of using one static large array of transducers, it uses the along-track displacement of the sensors to synthesize a large virtual array. The resolution thus obtained is in the order of the transducer element size and, most importantly, is independent of range and frequency. This potential resolution increase comes at the cost complexity in the image formation algorithms and tight sonar platform motion uncertainty tolerances: a fraction of the wavelength. Using a surface vehicle and a typical satellite navigation system, a synthetic aperture sonar can be operated directly from the navigation data, providing high quality high-resolution imagery suitable for applications such as river navigability, infrastructure maintenance and harbour surveillance. This book will focus on the advantages and limitations of using such synthetic aperture sonar and will examine the design and operation restrictions for a successful implementation.