Introduction to Precision Agriculture

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Introduction to Precision Agriculture

• Michael SpiessDepartment of Plant Science
• California State University, Fresno

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Precision Agriculture
Global Positioning Systems
Remote Sensing
Variable Rate Technology
Yield Monitors
Geographic Information Systems
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Precision Agriculture
Geographic Information Systems
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What is GIS?

• Maps Data

• Layers

• History

• Analysis by Location

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Why is GIS Important?

• Most data has a spatial component.
• GIS provides a method to
• Analyze the spatial component,
• Display the data spatially,
• And retrieve data spatially
• GIS is a MANAGEMENT TOOL
• Store traditionally collected data such as soil
  samples
• Foundation for Precision Ag.

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Farm GIS Layers

• Layers for
• Fields (Crop, Plant Date)
• Soil Map (Soil Type, Soil Class, S.I.)
• Fertility (N,P,K,.)
• Pump Locations (yields, pwl, last test, pump)
• Irrigation Distribution (pipe type, size)
• Streets (Name, size)
• Buildings (Name, Type)
• Aerial Photos
• Remote Sensing

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University Farm GIS

• Soil electrical conductivity indicates soil
  texture
• Data is collected with spatial location (DGPS)
• Plot represents 5100 data points

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Precision Agriculture
Global Positioning Systems
Geographic Information Systems
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What is GPS?

• A satellite based positioning system
• Three Segments
• Space Segment - 24 satellites
• Control Segment (Military)
• User Segment (GPS Receiver)

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GPS Constellation
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User Segment

• Units receive transmission from Satellites
• Cost between 100 and 25000 (depends on
  accuracy)
• Must be line of sight with satellites

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How does it work?

• Position of satellites is known.
• Satellite provides an electronic almanac to the
  receiver
• The speed of the radio signal from each satellite
  is known
• Very accurate timing allows the calculation of
  the distance from each satellite.
• Using triangulation, the position of the receiver
  is calculated.

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GPS
http//wwwhost.cc.utexas.edu/ftp/pub/grg/gcraft/no
tes/gps/gps.html
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Differential GPS (DGPS)

• Used to correct for errors
• Uses a ground station at a known location
• Ground station measures error of GPS signal by
  comparing the known location with the GPS
  location
• In real-time, the error transmitted to DGPS unit
  and position is corrected.
• Post-processing can be used when real-time is not
  needed.

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Differential GPS (DGPS)
http//wwwhost.cc.utexas.edu/ftp/pub/grg/gcraft/no
tes/gps/gps.html
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DGPS Signals

• US Coast Guard
• Near navigable waters
• Free
• Subscription Services
• FM (line of sight)
• Satellite
• Most of the Valley gets Coast Guard signal

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Accuracy

• GPS with Selective Availability on 50 m
• GPS with SA off 25 m
• DGPS 1-3 m
• Better accuracy is achieved by sampling more
  points (statistical)
• With local correction 2cm accuracy

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GPS Output

• Commonly Latitude and Longitude
• Latitude -- North/South position
• Longitude -- East/West Position
• Given in decimal degrees. Ex.-119.727289 36.8227
  58West Lon. North Lat.

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Using GPS Data

• GPS Unit stores data then data is downloaded to a
  computer
• GPS Unit has direct interface to computer
• GPS Unit is interfaced with
• Yield monitor
• Variable rate applicator
• Navigation guidance (parallel swathing)

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Precision Agriculture
Global Positioning Systems
Variable Rate Technology
Geographic Information Systems
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What is VRT/VRA?

• Also called Variable Rate Application (VRA)
• Site specific application of material
• Seeding
• Herbicide and Pesticides
• Fertilizer and Soil Amendments
• Material can be liquid or dry

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VRA

• Application Maps (GIS)
• Requires GPS location
• Method of creating map
• Sensor
• rate is varied by sensor on the applicator.

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Precision Agriculture
Global Positioning Systems
Variable Rate Technology
Yield Monitors
Geographic Information Systems
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What are Yield Monitors?

• Devices that record crop yields on a small area
• Typical area lt 100 Sq. Feet
• Fitted to the harvester
• Generate site-specific yield maps

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What is Required to Measure Yield?

• Measure quantity of crop.
• Volume (and moisture in grain)
• Weight
• Locate the sample
• DGPS
• Calculate the area
• Distance traveled
• Harvester Width (swath width)
• Adjust for measurement delay

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Crop Specific

• Grains
• Cotton
• Potatoes
• Peanuts
• Tomatoes

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Precision Agriculture
Global Positioning Systems
Remote Sensing
Variable Rate Technology
Yield Monitors
Geographic Information Systems
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Remote Sensors

• The majority are Electromagnetic (EM) spectrum
  detectors
• Panchromatic (visible as B/W)
• Multi-Spectral (MS)
• Hyper-Spectral
• May be fixed wing aircraft or satellite mounted

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Passive Detection

• Visible Light
• IR
• Microwave

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Normalized Difference Vegetation Index (NDVI)

• Used to depict vegetation
• Calculated from infrared and visible red(IR -
  Visible Red) (IR Visible Red)
• This value gives important information about the
  productivity or "greenness" and density of land
  vegetation.

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Applications to Ag

• Weather forecasting
• Mapping
• Wide area data
• Detection of crop problems
• Detection of crop growth/maturity

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Summary

• GIS and GPS
• Mature technologies in wide industrial use
• Variable Rate Technologies
• Improve application efficiency, potential for
  reduced environmental impact
• Yield Monitors
• Still in development for many crops, diagnostic
  tool
• Remote Sensing
• High potential as a management tool as cost drops

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More Information

• http//www.atinet.org/GIS/
• Precision Ag Listserv (International)
• CA Ag GIS Listserv