A METHOD TO ASSESS SPATIAL COORDINATES IN ART AND ARCHAEOLOGICAL OBJECTS - APPLICATION OF TOMOGRAPHY TO A DOLMEN

A method to determine the values of spatial coordinates of bodies, spe cifically adapted to study art and archaeological objects, was develop ed and tested on a dolmen made of granite in north-west Spain. This me thod, based on geometric principles, comprises an easy-to-assemble rig id structure as a physical support, and software based on the algorith ms discussed below, which together provide a rapid and inexpensive mea ns of assessing coordinates. One of the main features of this procedur e is the ability to quantify the accuracy of the coordinates being cal culated according to the quality of the input measurements. The simpli city of obtaining data means that the method can even be performed upo n rough and irregular-shaped objects, and in zones where other instrum ents are difficult to handle; for example, the interior of dolmens or small cavities. A demonstration of the method was performed upon an up right stone of a megalith in north-west Spain (Axeitos Dolmen, La Coru na). The coordinates of many points of measurement surrounding the obj ect, combined with parameters from ultrasonic signals, were used to ac hieve three-dimensional tomography. Considering the experimental error s produced by different operators, the accuracy achieved when estimati ng the coordinates was better than 1 cm. The tomograms obtained have b een employed to assist in the evaluation of damage to this megalith. ( C) 1997 Academic Press Limited.