Digital image georeferencing from a multiple camera system by GPS/INS

In this paper, the development and testing of an airborne fully digital mul ti-sensor system for digital mapping data acquisition is presented. The sys tem acquires two streams of data, namely, navigation (georeferencing) data and imaging data. The navigation data are obtained by integrating an accura te strapdown inertial navigation system with a differential GPS system (DGP S). The imaging data are acquired by two low-cost digital cameras, configur ed in such a way so as to reduce their geometric limitations. The two camer as capture strips of overlapping nadir and oblique images. The GPS/INS-deri ved trajectory contains the full translational and rotational motion of the carrier aircraft. Thus, image exterior orientation information is extracte d from the trajectory, during post-processing. This approach eliminates the need for ground control (GCP) when computing 3D positions of objects that appear in the field of view of the system imaging component. Two approaches for calibrating the system are presented, namely, terrestrial calibration and in-flight calibration. Test flights were conducted over the campus of T he University of Calgary. Testing the system showed that best ground point positioning accuracy at 1:12,000 average image scale is 0.2 in (RMS) in cas ting and northing and 0.3 in (RMS) in height. Preliminary results indicate that major applications of such a system in the future are in the field of digital mapping, at scales of 1:5000 and smaller, and in the generation of digital elevation models for engineering applications. (C) 2001 Elsevier Sc ience B.V. All rights reserved.