UAV systems for Parameter Identification inAgriculture

Eobin Alex George∗, Gaurav Tiwari†, R. N. Yadav†, Edward Peters‡ and Srishti Sadana†∗Department of Aerospace Engineering

Indian Institute of Science, Bangalore, Karnataka, India 560024Email: eobing@gmail.com

†Mansarovar Institute of Science and Technology, Bhopal - 462016, M.P., IndiaEmail: mailtogrv@gmail.com

‡CSIR AMPRI, Bhopal - 462016 M. P., IndiaEmail: edwardpeters@gmail.com

I. INTRODUCTION

Agriculture has changed from an art to a precision scienceusing high yielding and disease resistant genetically modified(GMO*) crop. Though GMO crops provide high yields theyare very sensitive to other factors like timely irrigation, nutrientconstitution of the soil etc. So it is important that these param-eters are periodically monitored to ensure their proper yield. Itis easy to monitor these parameters in a small field of an acreor less but it becomes almost next to impossible to consistentlymonitor them in large holdings of land. UAVs provide a fastand efficient method of analyzing field conditions in large landholdings. March 20, 2013

A. Current methods

Assessing agricultural land and crop condition is a key partof a viable and productive harvest. Conventional methods ofassessing crop conditions do not provide a quantitative analysisand is not reliable for large areas. Primarily the condition andstage of crops can be assessed by the following

• Ripening or stage of crops

• Irrigational condition

• Pest attack

• Nutritional requirement

Farmers with large holdings of land require a quick andeasy method of scanning their fields. They have to rely onunreliable, slow or unscientific techniques like time line basedapproach where the farmer roughly calculates the day ofharvest from the time of planting and certain environmentalfactors or by checking random samples of crop to assessripening. These methods are highly unreliable because of themany other factors which can change harvest times whichcannot be estimated accurately by farmers.

B. Application of UAVs

UAVs provide the best platform to assess land withouthav- ing to rely on unreliable, slow or unscientific techniqueslike time line based approach or by random crop checkingmethod. UAV systems are both fast and highly agile systemsallowing deployment in almost any environment. The onboard

systems give the operator easily interpretable data whichcan be used to further assess field health and condition byintensive post processing. This paper describes the use ofUAVs for parameter monitoring in agriculture, its implicationsand deployment. Since parameter identification is a very broadsubject with respect to aerial surveys, we restrict ourselvesto the identification of crop ripening here. The results areanalogous and can always be extrapolated to the identificationof other parameters.

II. METHODOLOGY

The complete system has the following parts:

1) Ground Station2) Aircraft

a) Airframe and power unitb) Payload

i) Image detection device(IDU)ii) Power unit

3) Telemetry unit4) Recovery device

The UAV is remotely piloted by a trained operator form theground station. The operator plans the survey mission with theguidance form the farmer before the actual flight to understandthe area, to determine his boundaries and the parameters hewants to identify and estimate. Depending on his requirement,the nature of land, availability of takeoff and landing area andthe airspace, the operator charts a flight plan. The operatorassesses wind direction, magnitude, lighting condition andproximity to other aircrafts etc. to determine the safest timeto fly. The operator then conducts the mission, surveys thearea for the required parameters and recovers the aircraft. Thedata is then further post processed and the images are given tofarmers along with the estimated parameters like crop stage,irrigational requirement and crop health. This data is providedalong with the GPS coordinates allowing the farmers to pinpoint the location and address the issue swiftly and efficiently.

A. Operation

UAVs remotely operated aircrafts which are controlled byan operator from a ground station. These aircrafts can beeither autonomous or semi-autonomous with a wide range of

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payloads depending on the mission objective. Aircrafts sizeand configuration vary depending on the

• Payload capacity

• Endurance

• Altitude of operation

• Operational range

The aircrafts can either be powered electrically using a highperformance Lithium Polymer Battery and a brushless motoror by an internal combustion engine conventionally usinggasoline. We could also employ jet turbine aircrafts whichcan be used for missions which require high altitude scansat higher speeds.The mission broadly consists of the following:

B. Aircraft Launch

Aircrafts can be launched in multiple ways.

1) Hand launch Small aircrafts under 1Kg class can belaunched by a person by throwing it. The aircraftthrottle is increased and the aircraft is simply handlunched.

2) Catapult In places where it is hard to find a smoothtake off strip, the aircraft can be launched from acatapult device. The catapult system can either bea bungee cord system or a compressed gas basedsystem to accelerate the aircraft to take off speed andlaunch it in to the air.

3) Runway take-off This is the conventional mode oftakeoff in cases where there is a smooth runway forthe aircraft to run, buildup speed and then take off.

C. Reconnaissance

Once the aircraft is air borne, the aircraft is guided tothe required location and altitude. The aircraft is then takenthrough a predetermined flight path to survey the requiredarea. This can be either done manually or autonomouslydepending on the aircraft system. The onboard Image capturingdevice (IMD) records images using a downward facing camera,along with a Global positioning system which records theaircrafts position. The flight paths for surveys are determinedby the nature of the features that are being surveyed. Landfeature monitoring like foliage and terrain are surveyed usingZ scans and geographical features like fault line and streamsare captured using Fly-by scans.

Fig. 1. Aircraft Scan Paths

D. Aircraft Recovery

The aircrafts have to be recovered after their mission. Theaircrafts have devices called high lift devices which help theaircraft to increase lift produced by the aircraft at low airspeedallowing the aircraft to land the aircraft at lower speeds.Recovery can be done by the following methods:

1) Normal Landing Normal landings are done in areaswhere there are smooth strips for the aircraft totouchdown. The aircraft is slowed down using highlift devices, aligned to the runway strip and thengently landed.

2) Parachute recovery In cases where there are nosmooth strips for the aircraft to land, the aircraft isrecovered by deploying a parachute after the aircraftis brought near to landing spot and slowed down toa safe speed for parachute deployment. The aircraftdescents to the ground with the help of a parachutecanopy which helps slow the descent rate for a safetouch down.

III. DATA RECOVERY AND POST PROCESSING

Data from the IMD and the GPS flight log are recoveredpost flight and are run through the software which extractsthe image frames from the video. The resulting image framesare analyzed by the software for the required parameters toreturn images that produce a positive match. The softwarefurther matches the timestamp with GPS log to return the GPSlocation of the image. The software returns both locations asGPS coordinates and also the aerial shot of the area.

Fig. 2. Data recovery and processing

The image frames returned can be compiled together eithermanually (initially) and then can be automated using a smallsoftware block. The image frames in a mosaic form givesthe end user a aerial view of the whole area allowing betterjudgment of the location and its features.

A. Agricultural Parameters estimation

Agricultural Parameters estimation Agricultural conditionscan be assessed directly from the data obtained from UAVaerial surveys. An array of parameters can be obtained from

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Fig. 3. Image Mosaic from Aerial Footage

raw data from the UAV depending on the Image capture device(IMD) payload in the UAV. The IMD can either be a visualspectrum camera or Infra-red spectrum camera. The currentUAV systems which have been tested with the Visual spectrumIMD, but the concepts can be extrapolated to other spectrumdevices like Infrared spectrum IMD, Visual spectrum IMDwith filters etc. Visual spectrum IMD can be used to estimatethe following parameters with a post processing unit. Theseparameters can be easily extracted from the data provided bythe UAV. The simple comparisons of extent of ripening in 2wheat fields are compared below to demonstrate the efficiencyand ease of this system. The histograph data of these imagesare also given which clearly shows the ripening extent of theRipe field due to low green levels. These parameters can beeasily extracted from the data provided by the UAV. . Thesimple comparisons of extent of ripening in 2 wheat fields arecompared below to demonstrate the efficiency and ease of thissystem. The histograph data of these images are also givenwhich clearly shows the ripening extent of the ripe field dueto low green levels.

TABLE I. AGRICULTURAL PARAMETERS THAT CAN BE IDENTIFIED BYUAV

Parameter Identification Estimated Crop condi-tion

Crop ripening stage Coloration and Nature Time to harvest

Crop irrigationalcondition

Coloration and Texture Regulate irrigation

Ripe crop spreadand percentage

Area of positive col-oration

Time to harvest

Crop nutrient defi-ciencies

Coloration and Texture Regulate Fertilizer appli-cation

Weed growth Coloration and Texture Weedicide application

Nature and spreadof Pest attacks

Coloration and Texture Pesticide application

Unauthorized activ-ities

Features and Boundary Land monitoring andcontrol encroachments

Fig. 4. Aerial image of a Ripe field

Fig. 5. Histogram of a Ripe field

IV. CONCLUSION

The use UAVs gives us an otherwise unseen perspective ofagricultural lands which can drastically improve agriculturalefficiency by efficient parameter identification and estimation.The conventional methods of crop condition analysis are takento a whole new level by utilizing aerial survey data. Not onlydoes this give us a more accurate data but allows predictionand estimation of critical information like appropriate harvesttime, optimum irrigational requirement, crop health and cropripening stage. The implications are endless. This system hasbeen currently employed in Kolar, Bhopal, Madhya Pradesh,India. The parameters are currently identified manually andthe automation software system is being optimized to detect

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Fig. 6. Aerial image of an Unripe field

Fig. 7. Histogram of an unripe field

and estimate the required parameters depending on nature ofthe crops under cultivation. This has given local farmers aconvenient method to assess crop harvest readiness withoutblindly relying on time lines for harvest or random samplingof crops. The cost are time saving by detecting pest attacks,moisture and nutrient content of the soil very early using UAVsgives farmers are worth mentioning here. Thought the cost ofthe this system is slightly on the higher side to be affordable fora single farmer, government subsidy and part ownership couldmake this a viable solution to improve farming efficiency ,help make farming a very profitable activity and help nationsattain food security.

ACKNOWLEDGMENT

The authors would like to thank the Mr. Harikumar Kan-dath, Researcher, Department of Aerospace Engineering, In-dian Institute of Sciences (IISC), Bangalore for his guidance inaircraft control systems, aerodynamics of aircrafts and sensors.We should also like to thank the Aerospace Engineeringdepartment, IISC and Mansarovar Institute of Science and

technology for sharing resources for conducting flight testsand generating test data to help prove the concept.

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