Airborne mobile mapping is one of the most important data acquisitionmethods for producing topographical maps and extracting terrain featuresfrom aerial images. The interest in 3D geospatial data is expanding, andtechnology is growing at an unprecedented speed with new digitalcamera mapping systems. Different sensors are used for data acquisitionin modern airborne photogrammetry. GNSS/INS (Inertial NavigationSystems) applications are developing, especially for direct georeferencingin airborne photogrammetry. Achieving accurately georeferencedproducts from the integration of GNSS and INS requires removingexisting systematic errors/bias, due to different reference systems, in themobile mapping systems. The collected data should refer to the samereference system; otherwise, it can impose a systematic shift in theresults. In this presentation, we assess the impact of the deflection ofverticals (i.e. the angle between the plumb line and normal to thereference ellipsoid) on the obtained horizontal and vertical coordinates.