Can I carry out GPR measurements in any climate?
GPR is a very versatile method and successful GPR measurements has been carried out in all climate zones on earth and in all kinds of weather. Ice, snow, rain and sun doesn’t matter, GPR is built to withstand all kinds of conditions. GPR equipment is usually temperature tested between -25 and +50 degrees Celsius, but normally works well also outside this temperature range, e.g. at Antarctica GPR has been used down to nearly -60 degrees. However, when weather conditions are extreme, there are number of things we need to pay attention to.
Measuring with electronical equipment in extreme weather conditions can sometimes be challenging. Cold weather reduces battery life and humidity can cause issues with moist. There are some tips and tricks that helps to reduce the risk of unsuccessful field campaigns.
Battery capacity: If possible, startup system indoors before exposing it to extreme cold temperatures. Insulate batteries using plastic foam or similar. over the battery on the antenna or around your battery bag to insulate. If towing behind a snowmobile, place the antenna in an insulted box.
Heavy rains The equipment is built to stand heavy rains. It should not be submerged but can be pushed/pulled through pools of water. Try to change batteries underneath some shield. Decrease the sensitivity of your tablet screen to avoid mis-taps. Place the tablet in a water-proof casing. Use a recording device, instead for pen and paper, to take notes.
Slippery measurements wheel Ice and snow can efficiently make you measurement wheel glide instead of spin. Use a measurement wheel with studs instead. Or if you are already out in the field, use a rope and wind it around the wheel.
Changing size of measurement wheel Snow can get stuck on the wheel and by that change the diameter, which again affects the distance measuring negatively. Use a GPS as positioning device instead, an external or internal, depending on the need of accuracy. Or work with pre-marked stretches and adjust the GPR profile length in your post-processing tool.
Snow cover Snow cover is seldom a problem, but the depth of your investigation will be limited, so it might be good to choose a lower frequency antenna. The snow cover, depending on the moisture and thickness, will affect the radar wave energy actually reaching the ground. But it should also be remembered that GPR is an excellent tool for mapping the snow cover, both in terms of thickness and internal layering.
Measurements on ice GPR measurements are made to investigate ice thickness, but also to investigate the actual freshwater lake. It is often easier to walk on ice instead of doing measurements form a boat. Measurements from ice works most often really fine, but when having zones of water within the ice, GPR can be though. This double layer may cause severe ringing. If possible, make measurements when you have only core ice conditions.
When ground frost is present, and especially as thawing has started, this may create one, or often two, distinct layers in the radargram. Sometimes the aim is to actually map the ground frost but if you need to investigate, e.g. a road, the ground frost layer may confuse the results as they easily can be interpreted as actual physical layers within the road. Be especially aware of this issue while interpreting if is suspected the ground frost has started to thaw and then become re-frozen. Local road authorities many times have information on ground frost conditions, contact them for more information prior to conducting your survey.
Salt on roads Road salts affects GPR measurements on the road or along the road negatively. The conductivity increases due to the salt and prevents GPR waves to penetrate the ground. Roads salts can affect the road for a long time before they have been flushed out by rain. There is not much to do about this, but if measurements are carried out in dry conditions (dry road construction and roadsides) the salt effects less.
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