On the premise of pos dislocation, how to select image control points?

Using the airborne POS system, the spatial position and attitude parameters of photos can be accurately obtained while taking aerial photos [1]. IMU/GPS (POS-assisted aerial photography) is an aerial photography technology which uses the combined measurement technology of inertial measurement unit (IMU) and global positioning system (GPS) to obtain the position parameters and image attitude parameters of the photography center at the moment of photography [2]. POS-assisted aerial photogrammetry integrates GPS and IMU devices with aerial cameras. GPS provides three line elements and IMU provides three corner elements. The integration of the three elements can obtain the directional elements outside the image at the same time, which greatly simplifies the work flow of aerial photogrammetry [3]. The experimental results of research institutions at home and abroad show that by introducing POS observations, the orientation results obtained by data processing methods of direct orientation (DG) or comprehensive orientation (ISO) with little or no ground control are basically equivalent to those obtained by traditional aerial triangulation methods [1]. POS-assisted aerial photogrammetry can reduce or even eliminate aerial stereo encryption and heavy field control work, greatly shorten the mapping cycle, reduce the cost, and solve the mapping problem in areas where ground control points cannot be laid.