Teaching our georadar how to ski

A curious and persistent cat likes to ride in our newly adapted georadar push cart. Foto: Petra Schneidhofer

Publisert:

23.03.2021

Oppdatert:

23.03.2021 kl.13.46

Winters in Norway can be cold and snowy. In order to be able to continue our monitoring surveys, we had to teach our georadar how to ski. After all, it's from Sweden ...

The VEMOP field season takes no winter break, and in the weeks after Christmas the weather in southern Norway turned proper cold with temperatures around – 10 degrees Celsius. Odberg is the test site that lies highest and furthermost inland, so it was no surprise that it was also the first one that got covered by snow.

However, given a “normal” Norwegian winter here in Vestfold, we had to expect snow on all four test sites. While a few centimeters of coverage do not inhibit us from using the wheeled push cart to guide the antenna across the survey areas, everything above 5 cm potentially poses a problem. In order to be able to continue our work, we had to come up with a cheap and easy-to-implement solution.  

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23 cm of snow at Odberg pose a problem to our single channel georadar. Foto: Erich Nau

One of the first ideas that came to our minds was to build a sort of sledge on which we could pull the antenna behind us across the surface. We ultimately decided against it for a few reasons: First, such a set-up would mean that we would compress the snow in front of the antenna through our footsteps. Second, potential lateral sliding of the sledge on uneven terrain would give us less control over the positioning of the radar-profiles. And finally, carrying and operating the relatively heavy GX controller unit plus the tablet with the navigation software on a chest harness while pulling the sledge behind us seemed not very practical.

After some back and forth, we decided to not re-invent the wheel (no pun intended), but go for the easiest solution that there is: Teach our georadar how to ski.

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Christer mounts fixtures and wooden blocks on to the skis. Foto: Petra Schneidhofer

Christer hunted down some used kid’s carving skis and mounted blocks and fixtures that would allow us to secure the wheels of our push cart to the skis. There were some discussions about what effect the metal edges of the skis would have and whether we should cut them off. We decided, however,  to leave them on and test the whole set-up (which was substantially delayed by one of my very curious and persistent cats, who at some point and under loud protest had to be vacated from the cart. The love these cats hold for the GX never ceases to amaze us).

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First tests at Odberg were promising. Foto: Christer Tonning

The ultimate test was performed at Odberg, which at that time was covered by around 15 cm of snow. We are happy to report that our set-up seems to work very well. The skis allowed us to push the antenna very smoothly across the surface, ensuring good antenna-ground coupling – something that was also noticeable in the data. In the weeks after, we successfully used our skiing georadar in varying conditions, even though 40 cm of freshly fallen snow taught us the limits of this set-up.

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The skis helped greatly in the various snow conditions at Odberg. Foto: Petra Schneidhofer

While we got away with a DIY solution for our single-channel georadar, fitting the 1.5 ton MIRA’s for use in snow is a whole different matter. But more on that in the next blog.


Emneord:

Geofysikk