In navigation, the azimuth corresponds to an angle measured from a north reference or a meridian, usually in clockwise direction. In SAR terminology, the azimuth direction corresponds to the direction in which the radar platform moves. The azimuth direction is also called along-track direction and is parallel to the flight path of the radar instrument. In a SAR image, the azimuth position of an object corresponds to its relative position in the field of view of the antenna following the radar’s line of flight. The azimuth direction is perpendicular to the range direction, which corresponds to the look direction of the radar antenna. The azimuth plays an important role in the definition of the azimuth resolution of a SAR sensor. Contrary to the range resolution, the azimuth resolution is independent of the distance between sensor and illuminated area and is constant. The azimuth resolution of a radar system corresponds to the beam width of the antenna on the ground, but can be improved using multiple successive real aperture acquisitions in order to form a longer, synthetic, aperture. This implies that an object on the ground is illuminated for a longer time and from different platform positions along the azimuth direction, inducing a Doppler frequency shift at the target. The use of specific synthetic aperture acquisition modes that steer the antenna along the azimuth direction, such as Spotlight mode, improve additionally the resolution in azimuth direction.