Standard focusing of SAR data assumes a straight recording track of the sensor platform. Small non-linearities of airborne platform are corrected for during a motion compensation step while keeping the assumption of a stripmap geometry. In the case of high resolution and high frequency SAR systems, the navigation data may not be accurate enough to perform such a motion compensation; SAR systems mounted on small aircrafts or drones flying at low altitude do not follow a straight track but one dependent on topography and atmospheric conditions. We present a blockwise focusing, mosaicking and geocoding method which allows processing such data. For the experiments, MEMPHIS and E-SAR data were used.