1. A method of determining the leading edge (E) of an object (P) comprising: mounting the object (P) in a desired position; positioning a light source (S) on one side of the object and viewing the object and its leading edge with an imaging means (I) positioned on the opposite side of the object; illuminating the object (P) with the light source (S), the object blocking a portion of the light from the light source (S) and the occluded portion of the light defining an outline (T) of the object including its leading edge (E); obtaining an image of the object (P) with the imaging means (I); moving the object (P) to a new position and repeating the above steps of illuminating the object (P) and obtaining an image of the object with the imaging means; and, processing the images using space carving techniques to ascertain the contour of the leading edge of the object whereby an accurate measurement of the leading edge can be made.