AGR638 C2

• AGR638 TOOLS OF PRECISION AGRICULTURE

  
• Tools of Precision Agriculture

  • GLOBAL POSITIONING SYSTEM (GPS)
  • GEOGRAPHIC INFORMATION SYSTEM (GIS)
  • REMOTE SENSING
  • INTELLIGENT DEVICES AND IMPLEMENT (IDI)
  • COMPUTER

  
• GPS (Global Positioning System)


  US satellite navigation system created and operated by the US department of defense

  
• GPS fully operated


  27 April 1995
• GPS satellites


  • Minimum capability of 24 NAVSTAR satellites in 12-hours orbits, 10600 miles above earth
  • Each satellite broadcasts a unique one-way coded signal toward earth

  
• GPS receiver


  Necessary to receive and track the coded signals from at least three satellites

  
• Almanac file


  Gives the satellite's exact position

  
• GNSS (Global Navigation Satellites System)


  Umbrella term for all satellite constellations that provide positioning data

  
• GPS


  • Satellites broadcast signal that allows GPS receivers to compute their locations
  • Provides real-time continuous position information

  
• Uncorrected GPS signals

  Accuracy of about 300 feet

  
• Corrected GPS signals


  Accuracy of 6-10 feet

  
• How GPS works


  1. Receiver calculates time (in billionth second) that signal took to travel from each satellite

  2. Uses this time to calculate exact distance from each of three satellites

  3. This process is called TRILATERATION

  
• Trilateration


  Process of determining the location of an object using the distance from at least three others points

  
• GPS in agriculture


  • Allows soil and crop measurement to be mapped
  • Allows users to return to specific locations to sample or treat those areas

  
• Factors affecting GPS accuracy
• Satellite clocks

  Atomic clocks in the satellite are not perfect, causing position estimation errors

  
• Satellite orbits


  Natural phenomena like gravitational forces and solar radiation create minor errors in satellite attitude, position and speed

  
• Earth's atmosphere


  Ionosphere slows the radio signal from satellite, causing delays
• Multipath errors


  Arise when GPS signal "bounce" around before getting to the GPS receiver, causing interference
• GPS receivers


  Noise due to electrical interference or rounding off can affect accuracy
• DGPS (Differential GPS) or SBAS (Space Based Augmentation System)


  Correction service to improve GPS accuracy
• RTK (Real Time Kinematic)


  Correction service provided by TRIMBLE company
• VRS (Virtual Reference Station)

  Correction service
• DGPS (Differential GPS)


  Uses a stationary base station at a known location to determine errors in satellite measurements, and sends correction to nearby moving receivers

  
• Data dictionary


  Outline of the objects that will be mapped and the characteristics or attributes that will be collected as data for each object
• Uses of GPS


  • Collecting and analyzing spatial data
  • Associating information with specific latitude/longitude locations

  
• GIS (Geographic Information System)


  Software system capable of displaying a digital map associated with an underlying database
• GIS database


  • Each record (row) represents a mapped feature, and each field (column) represents an attribute of the feature
• Factors considered in GIS

  • Social
  • Biodiversity
  • Engineering
  • Land Use
  • Environmental Considerations
• Intelligent Devices and Implements (IDI)

  Tools in precision agriculture that allow collecting data on various events or physical characteristics, or controlling equipment based on those characteristics

  
• Yield monitor system


  • Sensor to measure the amount of grain and other products passing through the combine harvester
  • Controller to record the yield data and associate it with location
  • Displays the yield data in real-time
• Database


  Represents a mapped feature, and each field (column) represents an attribute of the feature
• Database


  • The data can be stored, retrieved based on query of the data, or retrieved based on a query of map
• Factors considered in precision agriculture

  • Social
  • Biodiversity
  • Engineering
  • Land Use
  • Environmental Considerations

  
• Intelligent Devices and Implements (IDI)

  Tools in precision agriculture that allow the user to collect data on various events or physical characteristics of an object or to control some piece of equipment based on those characteristics

  
• Yield monitor system


  A good example of IDI because it has both sensors and controllers
• Yield monitor system


  1. Sensor to measure the amount of grain and other products passing through the combine harvester

  2. Sensor to measure the moisture of grain and other products

  3. Controller called a header switch that turns off data collection when the combine head is lifted
• Yield sensors

  • Impact or mass flow sensors
  • Weight-based sensors
  • Optical yield sensors
  • g-ray sensors
• Evaporative control weather system

  Has function to sense the surrounding microclimate conditions and use that data to control the amount of water being used to irrigate the area
• Sensors used in evaporative control weather system

  • Rainfall
  • Wind speed
  • Humidity