My students are looking to develop a device that can measure the thickness of ice and snow on a frozen lake. I have read that this is possible with RF through an article from MIT and I am wondering if anyone has tried something like this to get "ping" back from a RF signal and then use that to measure distance of the travel of the signal. Any help or direction would be appreciated.
mrturner147:
I have read that this is possible with RF through an article from MIT and I am wondering if anyone has tried something like this to get "ping" back from a RF signal and then use that to measure distance of the travel of the signal.
Can you tell us the technique used in the 'article from MIT' ?
It would work just like propagation of seismic waves.
the boundary layer between water and ice will have some reflectivity.
the speed of the wave, out and reflected is key so you have an idea how fast you need to listen for the response.
srnet:
Can you tell us the technique used in the 'article from MIT' ?
A summary would be helpful ...............................
Basically they shoot Wi-Fi through the wall and can see people on the other side. Using software it looks similar to a heat map. Thinking of using the same technology to "see" water on the other side of ice and then using the speed of the wave to measure the distance(thickness) of ice
Sonar would be much simpler. A cheap fish finder might even work.
Would the sonar go through ice and snow? And then bounce back off the water? Basically want ice thickness without the hole drilling.
mrturner147:
Would the sonar go through ice and snow? And then bounce back off the water? Basically want ice thickness without the hole drilling.
Yes. Generally speaking, material boundaries reflect waves. Sonar units have a minimum sensing distance and the ice would have to be thicker than that for the boundary to be sensed.
Drilling a hole is a pretty sure fire method of measuring ice thickness, and all you need is a steady supply of hot water.
You could try ground penetrating radar. Here's one DIY attempt at GPR in the GHz range...
Google says existing GPR tools for measuring ice thickness operate between about 2 MHz to 500 MHz.
I can think of a couple of practical problems that you/they might face.
First, RF energy in the commonly-available WiFi frequency bands are absorbed by water (which is why stuff gets hot in a microwave...) There may not be enough return signal after attempting to transit snow and ice and reflect off liquid water.
Second is a problem of time. If we use the speed of propagation of radio in a vacuum as a start (299792458m/s) and assume there is a return not badly attenuated by the water "ether", the transit time for a 10cm thick block of ice (so 20cm total) is 667pS (picoseconds; 667E-12 seconds...) In ice, light travels at ~2.29x10^8m/s so the transit time might be more ~875pS. Regardless: How will you accurately trigger and then measure the return time?
You could attempt to use a phase-detection method employed by commerical TOF sensors (e.g. http://www.ti.com/lit/wp/sloa190b/sloa190b.pdf) but adapting it for ice would be tricky.
srnet:
Can you tell us the technique used in the 'article from MIT' ?
Google Scholar on the lead investigator leads to this patent application. It's apparently a phased array chirped radar with image processing back end enabling a laundry list of applications described so as to make it patent-able.
Not clear how this is an Arduino project.
Look into ground penetrating radar.
Paul
google measuring paint thickness.
they do similar technology to measure the thickness of paint and coatings on cars and wall and such.
thickness device