accelerating the data-driven agriculture revolution · agriculture revolution colleen josephson...
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Accelerating the Data-Driven Agriculture Revolution
Colleen Josephson ([email protected])June 2019 1
Using Wireless Soil Moisture Sensors
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Theewaterskloof Dam in 2018near Cape Town, South Africa
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Nearly 70% of fresh water is used to grow food...4
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And more than 80% in Africa and Asia!
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Projected to reach ~10 billion by 2050!
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How do we feed 10 billion people when we’re already using 70% of our water on 7 billion?
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Precision agricultureUsing data to make decisions about water, fertilization, etc.
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20-50% water savings via soil moisture sensors!
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Why do <20% of US farms use moisture sensors?
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1. High sensor cost
● Average sensor is > $100● Excludes power source (e.g. solar panel)● Also excludes the ‘data logger’, which
collects and records measurements
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The Teros-12 soil sensor retails for $225
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$1 millionIs the cost of recommended sensor
deployment for the average 434 acre US farm
USDA Survey11
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2. Difficulty of deploying + maintaining sensors
● Installation● Waterproofing● Power harvesting● External tampering...like
curious cows
Wires, weather and watts
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3. Difficulty collecting + processing sensor data
3G/4G cellular module? Expensive.
Ad-hoc network? Failure prone.
Manual collection? Often tedious.
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(Fields don’t have WiFi)
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Microsoft’s Farmbeats
Uses a combination of drones, tractors and TV whitespace networks to collect sensor measurements and upload them to the cloud
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NSDI ‘17, D. Vasisht, et. al
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This talk will focus on
sensor cost-AND-
deployment + maintenance15
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What is soil moisture?volumetric water content
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How do sensors approximate soil moisture?
● Dielectric permittivity, ε, is ability of a substance to hold electrical charge
● Relative permittivity (sometimes dielectric constant):εr = ε/ε0
● εr changes as water content of soil changes →
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Topp equation (1983)
● Apparent dielectric constant Ka , function mostly of εr ● Soil moisture Θ related to Ka by the Topp equation:
θ = 4.3x10-6 * Ka3 - 5.5x10-4 * Ka
2 + 2.92x10-2 * Ka -5.3x10-2
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Time of Flight (ToF)
● Time an electromagnetic wave takes to propagate from A to B● Can approximate Ka (and therefore soil moisture) using ToF:
Ka ≅ (cτ/d)2
where c is speed of light, τ is ToF and d is distance
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Anything that gives accurate ToF can measure soil moisture!
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Soil Measurements Using RF (SMURF)2018 MSR Whitepaper, J. Ding
● Senses soil moisture using MIMO WiFi● Drawbacks:
○ Requires burying multiple antennas in soil
○ Limited WiFi chips give access to necessary info
○ Not very accurate
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What if we could use RF without burying wires?
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Backscatter: the scattering of radiation or particles back towards the source
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Passive vs. Active RF CommunicationsACTIVE PASSIVE
(backscatter)
amplifiers24
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~$2is the cost of agricultural RFID tags. With mass production,
our backscatter tags could cost similarly.
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Three parts of a backscatter system1. Excitation signal generator2. Backscatter tag3. Receiver
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Backscatter to sense soil moisture
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Accurate is ToF hard
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Two discernible pulses
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Pulse smearing: one big pulse
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Ultra-Wideband (UWB) Radar
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Experimentsetup
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Buried prototype
Ultra-wideband radar
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Backscatter prototype
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ultra-wideband antenna
RF switch
MCU (acts as oscillator)
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Isolating the backscatter signal
34Backscatter tag off Backscatter tag on
60 Hz ambient noise 125 Hz backscatter
Aliased backscatter harmonics
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Signal strength vs tag depth (preliminary)
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Commercial vs radar soil moisture (preliminary)
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Average difference between commercial sensor and radar measurements:
0.005cm3/cm3
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The long-term vision
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[S]mallholder farms operate on 12% of the world's agricultural land and produce 80% of the food that is consumed in Asia and sub-Saharan Africa...
https://www.cropscience.bayer.com/en/crop-science/smallholder-farming39
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Developing world [has] 98.7 per cent mobile phone adoption (as of 2017)
https://www.theregister.co.uk/2017/08/03/itu_facts_and_figures_2017/40
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59%Of the world owns a smartphone
http://www.pewglobal.org/2018/06/19/2-smartphone-ownership-on-the-rise-in-emerging-economies/41
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What remains?REMAINING WORK
● Experiment with more types of soil w/ ground-truth measurements
● Extend viable sensor depth range● Do experiments in a real farm field● Study effects of temperature and
soil salinity on the measurements
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LIMITATIONS
● Measurement time depends on radar frame rate and tag depth
● Environmental impact not understood
● Assumes relatively stable soil conditions
● FCC doesn’t currently allow unlicensed UWB below 3 Ghz
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Going forward: the bigger picture
● This system is just one small part ● New kinds of data at unprecedented volume and variety● Pressing need for systems to be mobile friendly
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Ag is one of tech’s final frontiers
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Sources● Deepak Vasisht, Zerina Kapetanovic, Jong-ho Won, Xinxin Jin, Ranveer Chandra, Ashish Kapoor, Sudipta N.
Sinha, Madhusudhan Sudarshan, and Sean Stratman, Farmbeats: An iot platform for data-driven agriculture, Proceedings of the 14th USENIX Conference on Networked Systems Design and Implementation (Berkeley, CA, USA), NSDI’17, USENIX Association, 2017, pp. 515–528
● Ranveer Chandra Jian Ding, Estimating soil moisture and electrical conductivity using wi-fi, (2018).● Topp, G.C., J.L. David, and A.P. Annan 1980. Electromagnetic, Determination of Soil Water Content:
Measurement in Coaxial Transmission Lines. Water Resources Research 16:3. p. 574-582.● https://www.cropscience.bayer.com/en/stories/2016/automated-agricultural-helpers-ripe-for-robots● https://www.gatesnotes.com/Development/FarmBeats● http://www.pewglobal.org/2018/06/19/2-smartphone-ownership-on-the-rise-in-emerging-economies/● https://www.theregister.co.uk/2017/08/03/itu_facts_and_figures_2017/● https://www.cropscience.bayer.com/en/crop-science/smallholder-farming
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