In the 1990s, combined use of GPS and inertial measurement unit (IMU) was studied to determine the orientation parameters during the photo flights in aerial photography.

• 20世纪90年代以来,国际摄影测量界开始研究采用GPS/IMU组合导航系统(POS系统)来获取像片摄影时的空间方位,以完全取代摄影测量加密。