The direct georeferencing in aerial photogrammetry requires precise measurement of position and attitude of an image sensor, because the object point position is computed directly using this data. But for several reasons, data from onboard inertial navigation system can not be used for this purpose directly. Especially GNSS antenna displacement and image sensor misalignment have to be compensated and different rotation and coordinate system conventions have to be taken into account. This paper describes the transformations of onboard GNSS/INS data for the needs of the direct georeferencing and demonstrates it on a real UAV photogrammetric mission.