Geopositioning of ADS40 three line images for large scale mapping

Airborne three line sensors now play more and more important role in large scale mapping, earth resource exploration, cyber city and other GIS applications. It can provide three stereo models for photogrammetric reconstitution. During the image acquisition, the equipped GPS/IMU system records the position and attitude data simultaneously and provides airborne sensors the capability of direct geopositioning. Currently GPS/IMU supported triangulation is still necessary for large scale mapping because of its limited accuracy, but because of the weak image geometry of three line sensor the adjustment is more complicated than that of the frame camera. This paper gives a comprehensive study on the triangulation of the imagery of airborne digital sensor ADS40. Linear polynomial, piecewise polynomial and orientation image three trajectory models are introduced. Considering that the object coordinate systems of ADS40 imagery are changing against strips, an algorithm to unify strip-wise exterior orientation (EO) parameters has been derived. Strip and block adjustment experiments are carried out. With no more than four control points the obtained position accuracy is better than 1.1 pixels on both horizontal and height directions.