An aerial photograph from July 1915 of the Turco area (left) is warped (middle) on a contemporary topographical map (right).

At present the nine previously mentioned selected zones are being more closely investigated by the C.A.I. (Centrale Archeologische Inventaris Central Archaeological Inventory) The focus of our attention currently lies on the processing of aerial photographs taken during the war. All warring parties built up a collection of aerial photographs taken above the Western Front, in advance of, during and after the different attacks. Millions of these photos can be examined in Great Britain, Belgium, Germany and France. The Box Collection of the Imperial War Museum (London), for instance, supplied us with a selection which are now being georeferenced in a G.I.S. (Geographical Information System - With thanks to Peter Barton and Nigel Steel for collecting these aerial photographs.). The computer recalculates the photo to fit on a contemporary map according to a number of indicated points, e.g. crossroads or structures; this technique is called image warping. Next, polygons, lines or dots on the modern map can indicate the structures visible on the aerial photograph. Trenches, barbed wire, tracks, old field boundaries, battery positions and other structures could be located exactly. This technique is applied on aerial photos of different periods; the results can be placed in overlay. In this way the evolution of the terrain can be thoroughly studied.