Our group (we are zoologists focusing on animal orientation) is considering buying a georadar to map the tunnels of subterranean mammals. We would like to study the position and direction of the tunnel networks of animals of various sizes (from voles to bigger animals such as ground squirrels, i.e., tunnels with various diameter in various depths) living in various types of soils and environments. When we received the visualization of our trial measurement of voles tunnels on the field, we were, however, a bit sceptical whether this is a suitable method (difficult to discern what is a tunnel and what some other anomaly such as rocks etc.).
Thanks!
Several time we have been able to see tunnels obviously caused by animals in the shallow subsurface using GPR. We used a 500 MHz Sensors & Software Noggin Plus with 25cm crossline spacing as well as 16-Channel 400MHz MALÅ Imaging Radar Array with 8cm crossline and 4cm in-line trace spacing. Both the 450MHz as well as the 700MHz should work in most ground conditions, since the tunnels mostly are very shallow. Crucial is the spatial sampling, i.e. crossline and inline trace spacing. What was the measurement spacing in your case?
Of course, the quality of the imaging always depends on the subsurface conditions. Wet clay will highly limit the penetration depth of the GPR pulse, while unsorted glacial moraine can contain a lot of stones causing a disturbed image.
Here a depth-slice from ca. 25 cm depth in Scandinavian soil (pasture) showing animal burrows. I am not sure whether these are the burrows of moles, voles or rabbits, but I think it is moles. Recorded with a 16-channel MIRA 400 MHz array with 8cm crossline and 4 cm inline trace spacing. These are amplitude slices after Hilbert transformation. You may wish to consider coherence processing of your data in order to better image small structures. Have a look at my recent paper on that method: Article Beyond Amplitudes: Multi-Trace Coherence Analysis for Ground...
Thanks for your answer, Immo! It´s reassuring to see that it is possible!:) As I wrote, we are zoologists with no experience in these technologies. I see, that there are many factors to consider - the spacing of lines, antenna, substrate, and the data processing and tranformation. Regarding the spacing - I do not know the terminology, but I think there were 10 cm lines... We did just demonstration measurement and picked random field site and we did not do any adjustment at all which probably would actually help. Thanks for the attached paper!
Thanks, Niklas! That is indeed really nice and thoroughly conducted study! :) I am already in contact with Adam Booth.
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