1. A computer implemented method for use in estimating a pose of an imaged object, the method comprising the following steps: a) receiving an image made up of image elements, the image representing, in three spatial dimensions, a scene including the imaged object; b) for each of a plurality of the image elements, identifying one or more corresponding candidate locations in an atlas of one or more candidate objects; c) forming a pair of image elements from the plurality of image elements, the pair comprising a first image element and a second image element; d) determining a first distance between the first image element and the second image element; e) determining a second distance between a first candidate location corresponding to the first image element and a second candidate location corresponding to the second image element; and f) comparing the first and second distances.