Sensor Model for Airborne Ccd Linear Scanners

This paper describes a sensor model for the georeferencing of imagery acquired by CCD linear array sensors with along-track stereo viewing carried on airplane. The model consists of two main algorithms for direct and indirect georeferencing. If positioning instruments (GPS,INS) provide the sensor external orientation (position, attitude) during the image acquisition, the ground coordinates of points measured in 2 or more stereo images can be estimated through a forward intersection, taking into account the displacements between the reference systems involved (direct georeferencing). On the other hand the indirect georeferencing algorithm is used when the sensor external orientation is not accurate enough. In this case the sensor external orientation is modeled with 2 or 1 order polynomials depending on time, with constraints on the continuity of the functions and their first and second derivatives between adjacent segments. Moreover the internal orientation and systematic errors due to lens distortions and CCD lines rotations are estimated with self-calibration. Using well distributed Ground Control Points (GCPs) and, additionally, Tie Points (TPs), the external orientation and self-calibration parameters, together with the TPs ground coordinates, are estimated in a least-square adjustment. The direct and indirect georeferencing algorithms are designed for singleand multi-lens optical systems. In case of multi-lens sensors, additional parameters describing the relative orientation of each lens with respect to the central one are introduced.