Building aerial mosaics for visual MTI

Abstract

This paper addresses the task of making a mosaic from images gathered by a down-looking camera on an airborne platform. This is in the context of a system to detect and map the positions of moving objects. We present three mosaicing approaches based on integrating together sets of measured pairwise homographies, i.e. geometric relationships, between overlapping image frames. The methods are simple chaining, consensus placement and bundle adjustment. We have demonstrated all the approaches with simulated data whilst the simplest way of using pairwise links, simple one-dimensional chaining, has been demonstrated with real data. In our bundle adjustment method, we use a two-dimensional network of pairwise links; when each frame is added to the mosaic, all the constituent frames are adjusted with respect to each other so that the consistency over the entire network is optimised. We have successfully shown, in simulation, that the bundle adjustment technique results in much more consistent, undistorted maps.