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This company claims that they can determine accurate irrigation patterns on a terrain just by using 3 sensors (https://www.youtube.com/watch?t=80&v=U48XTXXi_MA).

They don't talk about the actual sensors or how they work, but there are not many variables you can measure besides chemical composition of soil and impedance, so I assume the use the 3 sensors to measure impedance between them (here you can see the actual sensor https://youtu.be/AXUlxaatpYY?t=16s).

As you can see in the picture, they deliver soil humidity patterns that seems very specific: enter image description here

The picture not only shows how much water there is on each sensor but it also builds a map distribution of the water on the soil. Theoretical speaking, how do think they do it?

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Note that the sensor placement is "guided by the app". They are undoubtedly combining the sensor data with other sources of data, such as weather reports and geophysical soil and topography data, and using the sensors to calibrate their models.

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  • \$\begingroup\$ "geophysical soil and topography data" down to a few meters precision? I don't know any DB that precise, unless you create it adhoc for each client inspecting their terrain. Other way I don't believe that data exist. \$\endgroup\$
    – DomingoSL
    Aug 21, 2015 at 20:11
  • \$\begingroup\$ You't be surprised at what exists. I've been involved with a couple of aspects of "precision farming" for a while now, including precision navigation for the tractors themselves, as well as multispectral aerial photography to evaluate crops. \$\endgroup\$
    – Dave Tweed
    Aug 21, 2015 at 20:17
  • \$\begingroup\$ that pretty cool but "precision navigation" and "aerial photography" has nothing to do with this geophysical soil database precise down to meters you theorize, again, I don't thing that data exists if you don't create it for each farmer who buys the product, and it do not seems to be the case here. This is a very small startup claiming to being able to operate in any part of the globe... \$\endgroup\$
    – DomingoSL
    Aug 21, 2015 at 20:23
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    \$\begingroup\$ I know nothing about CropX; I never heard of them until just now. You asked for theories about what they might be doing, and based on my knowledge of the field, I forwarded a plausible hypothesis. You CAN infer a lot about the underlying soil and its drainage characteristics from historical photosurvey data, and that data is available commercially down to sub-meter resolution. I'm saying that it is entirely possible that they have developed a mathematical model of how soils, crops and water interact, and they just need a few sensors worth of "ground truth" to keep that model calibrated. \$\endgroup\$
    – Dave Tweed
    Aug 21, 2015 at 20:30
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After days of research I finally understand how it works. As mention by @Dave Tweed there are commercially available soil maps precise down to a few meters, but his answer was lacking of references. I actually find an impressive tool that allows you -for free- to download GIS data about different soil characteristics.

enter image description here

So using the sensors I assume they measure impedance to calculate soil humidity to have a real time input about how fast the terrain drains, this sensors are placed in the different soil areas that actually behave differently so they can compare the theory model with the actual behavior, calibration. I suppose they also combine elevation data a sun exposure (data way more easy to find) to have a better mathematical model.

Then, the telemetry part and cloud communication is the easy part of the game.

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