intro to pa

8/8/2019 Intro to PA

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Introduction to Precision

Agriculture

Michael Spiess

Department of Plant ScienceCalifornia State University, Fresno



Precision Agriculture

GlobalPositioning

Systems

Geographic Information Systems

RemoteSensingVariableRate

Technology

YieldMonitors



What is GIS?

Maps + Data

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³Layers´

Analysis by Location

History



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 M ANAGEMENT TOOL Store traditionally collected data such as soil

samples

Foundation for Precision Ag.



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



University Farm GIS

Soil electricalconductivity indicatessoil texture

Data is collected withspatial location(DGPS)

Plot represents 5100data points




GlobalPositioning

Systems




What is GPS?

A satellite based positioning system

Three Segments

± Space Segment - 24 satellites ± Control Segment (Military)

± User Segment (GPS Receiver)



GPS Constellation



User Segment

Units receive transmission from Satellites

Cost between $100 and $25000 (depends

on accuracy) Must be line of sight with satellites



How does it work?

Position of satellites is known.

± Satellite provides an ³electronic almanac´ to thereceiver

The speed of the radio signal from eachsatellite is known

Very accurate timing allows the calculationof the distance from each satellite.

Using triangulation, the position of thereceiver is calculated.



GPS

http://wwwhost.cc.utexas.edu/ftp/pub/grg/gcraft/notes/gps/gps.html



Differential GPS (DGPS)

Used to correct for errors

Uses a ground station at a known location

Ground station measures error of GPSsignal by comparing the known location withthe GPS location

In real-time, the error transmitted to DGPSunit and position is corrected.

Post-processing can be used when real-timeis not needed.



Differential GPS (DGPS)

http://wwwhost.cc.utexas.edu/ftp/pub/grg/gcraft/notes/gps/gps.html



DGPS Signals

US Coast Guard

± Near navigable waters

± Free Subscription Services

± FM (line of sight)

± Satellite

Most of the Valley gets Coast Guard signal



Accuracy

GPS with Selective Availability on: 50 m

GPS with S A off: 25 m

DGPS 1-3 m Better accuracy is achieved by sampling

more points (statistical)

With local correction 2cm accuracy



GPS Output

Commonly Latitude and Longitude

Latitude -- North/South position

Longitude -- East/West Position Given in decimal degrees. Ex.-119.727289 36.822758

West Lon. North Lat.



Using GPS Data

GPS Unit stores data then data isdownloaded to a computer

GPS Unit has direct interface to computer GPS Unit is interfaced with:

± Yield monitor

± Variable rate applicator ± Navigation guidance (parallel swathing)




GlobalPositioning

Systems


VariableRate

Technology



What is VRT/VRA?

Also called Variable Rate Application (VR A)

Site specific application of material

Seeding Herbicide and Pesticides

Fertilizer and Soil Amendments

Material can be liquid or dry



VRA

Application Maps (GIS)

± Requires GPS location

± Method of creating map Sensor

± rate is varied by sensor on the applicator.




GlobalPositioning

Systems


VariableRate

Technology

YieldMonitors



From: http://agronomy.ucdavis.edu/plant/precisag.htm

What are Yield Monitors?

Devices that record cropyields on a small area

Typical area < 100 Sq.Feet

Fitted to the harvester

Generate ³site-specific´yield maps



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



Crop Specific

Grains

Cotton

Potatoes Peanuts

Tomatoes




GlobalPositioning

Systems


RemoteSensingVariableRate

Technology

YieldMonitors



Remote Sensors

The majority areElectromagnetic (EM)spectrum detectors

Panchromatic (visibleas B/W)

Multi-Spectral (MS)

Hyper-Spectral May be fixed wing

aircraft or satellitemounted



Passive Detection

Visible Light

IR

Microwave

Sensor

Reflecting Surface

Source



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 densityof land vegetation.

Normalized Difference

Vegetation Index (NDVI)



Applications to Ag

Weather forecasting

Mapping

Wide area data Detection of crop problems

Detection of crop growth/maturity



Summary

GIS and GPS

± Mature technologies in wide industrial use

Variable Rate Technologies

± Improve application efficiency, potential for reducedenvironmental impact

Yield Monitors

± Still in development for many crops, diagnostic tool

Remote Sensing

± High potential as a management tool as cost drops



More Information

http://www.atinet.or g/GIS/

Precision Ag Listserv (International)

C A Ag GIS Listserv

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