1. A method of calculating a transform matrix for transforming points in a model of an object to an image of the object captured by a camera, the image providing a two dimensional view of the object, the object having a plane, which includes a plurality of lines or edges defining features on the plane of the object, the method comprising identifying a plurality of triplets of points on the lines or edges of the object in the image from the camera, each of the triplets providing three or more non co-linear points on the lines of the object in the plane of the object, identifying a sample triplet of points in the model, for each of the identified plurality of triplets, calculating a transform matrix which will transform the sample triplet from the model onto the identified triplet from the camera image, for each of the identified transform matrices, calculating a transformation of a plurality of points on the lines of the object in the model, calculating a comparison metric between lines formed between the triplet of points transformed from the lines of the object in the model and corresponding lines between the triplet of points in the image view of the object, and identifying the transform matrix which produces the best comparison metric, the identified transform matrix being for use in transforming points on the model into the image produced by the camera, or points in the image onto the model.