Oklahoma Established Program to Stimulate Competitive Research (National Science Foundation). Research Experiences for UndergraduatesGeological Survey (U.S.)Electrical Engineerin

Captain, Levi

Ekin, Sabat

Hossain, Fahim

Jacob, Jamey

Messenger, Russ

Taghvaeian, Saleh

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Soil Moisture Monitoring with LoRa Radios and UAVsLevi Captain*, Fahim Hossain*, Russ Messenger*, Dr. Jamey Jacob§, Dr. Saleh Taghvaeian†, Dr. Sabit Ekin*, Dr. John O’Hara*Oklahoma State University *Electrical and Computer Engineering§Mechanical and Aerospace Engineering†Biosystems and Agricultural EngineeringIntroductionSoil moisture levels are critically important to cropyields, yet they are often estimated based onexperience, visible signs of stress in crops, and/orfeel of soil. Soil moisture sensors add badly neededprecision to watering but are often inconvenient forfarmers due to reasons such as:• They require wired power or regular batterymaintenance• The equipment (antennas and sensors) arepartially located within crops above ground,creating obstacles for field equipment to avoid.[1]• They have short signal range, require wirednetworking, or manual data retrieval. [2]We present a low-power, fully wireless IoT solutionthat utilizes completely buried sensors and UAVs tomeasure, record, and convey soil moisture levels.MaterialsThe system capitalizes on three major elements:• The unmanned aerial vehicle (Phantom 4 UAV).• Long Range wireless radios (LoRa)• Capacitive style soil moisture sensorsOther equipment used in this research• Raspberry Pi• GPS Module• USB BatteriesConclusions• The system behaves better than expected,exhibiting strong signal strengths at largetransverse bounds and higher altitudes orheights.• The RSSI values indicate a very largecommunication link margin is available,suggesting that crop cover should notadversely affect the system performance.• The system is very insensitive to polarizationmisalignments.• The system is robust, easy to set up and use,and easily adaptable to other sensingapplications.• With some protocol and hardware tuning,sensor battery life is expected to be on the scaleof several months.• The system operates at heights great enough toclear the height of any crops it may be usedwith.Importance• According to a recent study by the USDepartment of Agriculture, only 89 of 78,531farms use soil moisture monitoring to determinewhen to water crops. [3]• Water usage in Oklahoma is quickly rising andmust be managed more deliberately.• According to the EPA, topsoil erosion is theleading cause of pollution of lakes and rivers.This erosion can be attributed to overuse of water,among other things. [4]• The technology of this system can be applied tocontrol and monitor the effectiveness of irrigationmethods and to measure other important soilproperties.Research Goal, Method, and ResultsAcknowledgments (Thank you!)• OSU-VPR, Summer Research Expo• OK NSF-EPSCoR Award #OIA-1946093 • USGS Award #G16AP00077• OSU Unmanned Systems Research Institute • Taylor Mitchell, Allan Burba, and Andrew ColeReferences1. Trellis soil moisture monitoring systems: https://mytrellis.com/2. Akyildiz, I.F. and Stuntebeck, E.P., 2006. Wireless underground sensor networks: Research challenges. Ad Hoc Networks, 4(6), pp.669-686.3. United States Department of Agriculture: 2017 Census of Agriculture: https://www.nass.usda.gov/Publications/AgCensus/2017/index.php. 4. Five Major Challenges Facing North American Agriculture: http://seedstock.com/2012/04/18/five-major-challenges-facing-north-american-agriculture/.Parallel Polarization Tests• The antenna mounted on the drone and the antenna mounted on the buried LoRa transmitter are parallel.• 4,000+ RSSI measurements were collected at heights of 3, 6, 9, 12, and 15ft in an approximately 150 ft x 150 ft square centered on buried transmitter.• RSSI indicate very usable communication is possible (RSSI > –80dB) at all heights, even out to transverse distances > 70ft.Goal:• To determine if buried LoRa radios produce sufficiently strong signals in propagation through various soils to enable communication of soil moisture data to a UAV-based LoRa receiver hovering overhead, and to determine the communication link margins via determination of RSSI (received signal strength indicator).Method:• Buried LoRa radios convey soil sensor data wireless a short distance through the ground with very low power and excellent battery life.  • The UAV has a LoRa receiver as payload and visits each sensor to collect data.• Soil sensors buried at 1 foot deep with antenna polarization recorded.• Measurements validated with research grade sensor (Campbell Scientific Hydrosense II)• Soil moistures during measurements ranged from 3 feet to 15 feet.Cross Polarization Tests• The antenna mounted on the drone and the antenna mounted on the buried LoRa transmitter are perpendicular.• 4000+  RSSI measurements were collected at heights of 3, 6, 9, 12, and 15ft, in an approximately 150 ft x150 ft square centered on buried transmitter.• RSSI indicate very usable communication is possible (RSSI > –80dB) at all heights, even out to transverse distances > 70ft.

Soil moisture monitoring with LoRa radios and UAVs

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Soil moisture monitoring with LoRa radios and UAVs

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