Photogrammetric image registration (PIR) of MTI imagery

This paper describes the use of photogrammetric principles to georeference imagery collected by the Multispectral Thermal Imager (MTI) satellite. The photogrammetric image registration (PIR) method consists of two main parts. The first part estimates a trajectory (exterior orientation as a function of time) for the sensor based on a photogrammetric bundle adjustment governed by user defined ground control points. The ground control points are defined by manual identification of conjugate points between the LEVEL1B_U imagery and reference data (an orthoimage and a digital elevation model derived from aerial photography). The second part uses this trajectory as input to a direct georeferencing method to determine the location of each pixel in the imagery. The PIR method uses mathematical models of the sensor, its trajectory, timing, and the terrain to mimic the actual image acquisition event. It was found that accurate calculation of the exterior orientation parameters was not a requirement to obtain accurately georeferenced imagery. This is particularly intriguing, and deserves more in-depth study, because the values of the exterior orientation parameters solved for through photogrammetric bundle adjustment are known to be in disagreement with the actual motion of the satellite platform. The individual steps of the PIR method, the mathematical models used, and the results of georeferencing MTI imagery through the use of this approach are described.