A multi-sensor system for airborne image capture and georeferencing

The development and preliminary testing of a fully digital multi-sensor system for airborne remote sensing and geographic information system (GIS) applications is described. This system was developed at The University of Calgary in collaboration with The University of California at Berkeley, with aircraft and logistics support by HJW Inc., California. it integrates a medium class inertial navigation system (INS), two low-cost Global Positioning System (GPS) receivers, and a high-resolution digital camera. During aerial image capture, camera exposure stations and INS digital records are time-tagged in real time by GPS. The INS/GPS-derived trajectory parameters describe the rigid body motion of the carrier aircraft. Thus, they are directly related to the parameters of exterior orientation. During post processing, these parameters are extracted, eliminating the need for ground control for airborne image acquisition applications. Flight tests were performed over a part of the university campus at Berkeley, using a strip photography approach to test the integrated system performance. In this paper, the concept of direct georeferencing of digital images without ground control is presented. System calibration results are then discussed in some detail, and special attention is given to the geometrical analysis of the system imaging component. An improved imaging system is proposed and validated by computer simulations. The potential of the new system for photogrammetric use is then discussed. The major applications of such a system will be in photo ecometrics; the mapping of utility lines, roads, and pipelines; and the generation of digital elevation models for engineering applications.