Digital Terrain Modelling
Also known as Digital Elevation Modelling, Digital Terrain Modelling (DTM) allows the visualisation of the surface of monuments and archaeological features. By accurately measuring the height of the land using RTK GNSS, total station or obtaining heights derived from LiDAR data and aerial photography, surface detail can be expressed as a digital image or as contours. We can enhance surveys using hachures and lines and polygons to highlight features of archaeological interest. The models can also be combined with geophysical data in order to provide an extra dimension to analysis. Most of our magnetometry survey interpretations are aided by DTMs produced from height data captured by our cart based system during the fieldwork or from freely available LiDAR datasets.
A range of functions can be carried out on the data to enhance certain visual aspects of the model such as height exaggeration and lighting effects. The model of Castle Combe castle below was produced from data collected in dense woodland and the site can now be visualised as never before.
Digital Terrain Model of Castle Combe 12th century motte and bailey castle.
DTMs also prove valuable in eliminating anomalies of modern origin from magnetometry or resistivity data. For example, where linear anomalies correlate with shallow surface depressions on agricultural land, this is often an indication of relatively modern land drainage channels. Areas of modern dumping or ground disturbance may also be visible within the models.