Relative positioning from model indexing

We show how to determine the position of a camera relative to a model of the environment using features extracted from one image. The method is based on view variation of cross-ratios and is independent of camera calibration. 1 Model Indexing From Images Recognition and pose estimation of objects in images is in general based on extracting features such as points and lines from the image and finding corresponding features in model objects. The combinatorial complexity of matching image descriptors to models can be considerable. A way to reduce this is to use index tables where image descriptors are used as indexes to a table containing corresponding model descriptors. These tables can be constructed off-line which means that space is traded off for time [1] [2] [3] [4]. Another factor affecting the complexity of recognition is the fact that the image of an object, depends on the viewpoint of the camera. This has initiated work in finding feature descriptors invariant to viewpoint [1] [2]. For configurations o