Abstract: Synthetic Aperture Sonar (SAS) is a high-resolution acoustic imaging technique which is an extension of normal sidescan sonar imaging. The cross-range (azimuthal) resolution in real aperture sonar is dependent on distance to the illuminated scene and signal frequency. Moreover, required azimuth resolution usually needs a beamwidth narrower (enlarged real aperture) than what can be achieved in practice by sized physical antenna. Synthetic aperture sonar overcomes all these constraints, which are discussed in this paper. The specific mode of SAS explained and analyzed here is known as stripmapping. In this mode, platform which contains a transmitter and a receiver, emits consecutively pulses to the examined area in range direction, which is perpendicular to the direction of travel. An appropriate coherent combination of received echos leads to formation of synthetically enlarged aperture. Synthetic aperture processing allows to obtain a high-resolution image of the examined seafloor. This paper covers basic SAS processing algorithm and shows some results of numerical simulation.