Doing anything on a frozen lake can carries some amount of risk. Nevertheless, every year events ranging from car racing to ice skating are held on them. As such, proper safety precautions are needed, the most important of which is ensuring the ice is thick enough to withstand the weight of whatever may be on it. This is done by cutting holes into the ice and measuring its depth in several locations. But this is a dangerous and imperfect process only giving a rough picture of actual thickness. So to solves these problems, a team of students at ETH Zurich made an ice measuring submersible drone.
The concept of ice measurement employed is, on paper, reasonably simple. When a sonar pulse is sent out, some of the energy will return off the bottom of the ice sheet, but some of it will pass through creating a second return. By measuring the difference in these two returns, the thickness can be calculate with a high degree of precision. Attach the sonar to a submersible and give it a positioning system and you can simply get a thickness map, right? Well, employing theory in practice is a far more complicated prospect as the students soon found out.
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