GPR Tomography and Iso Projection of archaeological features

12.10.2022, 14:28

Archaeology

GPR has long been used to determine archaeological features before any intrusive works begin. This is partly due to the desire to protect the archaeology in situ, without the need for destructive excavation processes.

KB Surveys visited an archaeological excavation in progress to offer a small test GPR survey area in the hope that the survey would increase the understanding of the site without widening the excavation.

The survey was approximately 15m x 35m and was performed using an orthogonal approach. The post-site processing revealed archaeological features within the test area. Further processing produced a tomographic image of the area with the features included.

The image above is an overlay tomographic image of the test area. This means that the high reflection material (GPR uses reflected signals from different sub-surface materials to determine location and depth) at different depth slices has been overlaid to produce an overall feature representation in the data.

The red is the higher reflective material, which clearly shows archaeological activity.

GPR surveys allow for accurately mapping subsurface so the digging activities can be localised and give archaeologists idea on how deep to dig without damaging historically valuable structures.

This above image is the same tomographic image but the features have been highlighted for clearer understanding of the site.

The red circles appear to be buildings, possibly Iron Age. The yellow feature is most likely a kiln oven (as others had been found on the site approximating those dimensions) and the dark blue circle is possibly another kiln.

To further the results, an Iso was created. This follows the same idea as Overlaying but does it in a 3-D format to give a depth to the feature which 2-D tomography does not.

Above is discussed visual representation of the Iso rendered GPR results. Although much clearer on an interactive platform in 3D, it is clear to see the areas of archaeological material within the ground.

The Iso rendering allows the high reflective material to be put into a 3D model, similar to the tomographic but in 3 dimensions instead of 2.

The applications for this can be considered widely useful for the interpretation of data when in search of features.