Topographic survey can used to both record visible features and to reveal residual elements of ancient landscapes otherwise invisible to the naked eye. The complementary nature of topographic and topsoil magnetic susceptibility mapping has been extensively explored by Oxford Archaeotechnics and continues to be the subject of current research. Oxford Archaeotechnics use a servo-driven total station employing active target tracking capable of recording thousands of data points per day. This dense coverage can be computer processed to generate a variety of plots with contour, 'wire frame', false relief and shaded image plots among the options depending on the nature and physical characteristics of the survey area.
Below: Topographic survey: false relief plot (8,000 data points). The Z values have been amplified to model the extremely subtle height variations . A fen edge arable land block measuring approx 1 x 0.5 km (50 ha). In the field only the lower half of the large curvilinear bank is obvious to the eye. The extremely subtle sw-ne lineations may be of early prehistoric origin; other elements relate to later prehistoric, Romano- British and medieval land use. This site has also been the subject of global topsoil magnetic susceptibility mapping (10m resolution) and total magnetometer survey: the results are complementary and provide a unique overview of the landscape prior to further archaeological investigation.
Below: A Saxon earthwork in woodland, SE England, surveyed and modelled to assess quarry damage (120 x 60m with 3,000 data points logged). A substantial bank extends into the survey area from the north (top). Much of the southern and eastern sides of the earthwork were destroyed by gravel quarrying at the end of the last century. Topographic survey has defined the surviving extent and form of the largely overgrown earthwork within the wood and mapped the precise limits of destruction and disturbance caused by the quarry . Oxford Archaeotechnics have considerable experience in woodland topographic work where fieldwork skills and specialized equipment have been used to record hundreds of features of archaeological potential preserved within woodland contexts where contemporary earthwork features been eradicated from the surrounding landscape by prolonged agricultural activity. The use of active remote targets and servo-driven tracking allows survey stations to be established with comparative ease in areas of restricted visibility; the subsequent data logging can be undertaken rapidly without the need for either manual adjustment of the total station or the need for the operator to maintain visual contact with the prism.
