Why we use two GPR systems for monitoring

The two GPR systems used for VEMOP: a motorised, multi-channel MIRA and hand-pushed, single-channel GX Foto: VTFK




07.12.2021 kl.14:57

It has been a while since we last posted an update on VEMOP. So, what happened these last six months?

A lot, and when we say a lot, we mean a lot of walking, respectively driving. We continued to concentrate on conducting monitoring surveys on our four test sites Heimdal, Hovland, Lunde and Odberg with both our measurement systems: the motorised multi-channel MIRA owned by NIKU and the hand-pushed single-channel GX owned by VTFK.

There are a number of reasons to use two different GPR systems for our project. One is to ensure that we have a complete, continuous set of monitoring surveys with the same system for comparability reasons. The MIRA is one of only four motorised ground penetrating radar systems in Norway and its usual job is to work as a primary investigation tool in cultural heritage management as well as in archaeological research. When we set up VEMOP, we had to take into account the possibility that it would not always be available to us when we needed it or that it would be not ready for use due to the frequent maintenance these heavily-used machines require. Even if, in the end, that was not the case, it was important for us to be prepared and have a second GPR system available at all times – the GX.

Another reason, and one much more relevant to the actual focus of the project, is the fact that the MIRA and GX are both operated using their respective parameters and that becomes most apparent when looking at their spatial sampling strategies: 2-4 x 25cm for the GX and 4-6 x 10cm for the MIRA. The crossline spacing alone makes a large difference in whether or not potential archaeological structures can be identified in a GPR data set. As both systems are used regularly for CHM and archaeological research purposes in Norway, we wanted to make sure that these differences are represented in VEMOP.  

The last six months encompassed quite a variety of environmental conditions. A changeable spring, a relative hot and very dry summer, a wet autumn and an early cold spell at the beginning of December challenged our in-situ measurement equipment and even claimed a victim. More on that in the next blog.


Geofysikk Arkeologi