Getting the Value fromGetting the Value fromGuidance Systems, Light Bars, and GPSGuidance Systems, Light Bars, and GPS

Marvin Stone

Biosystems and Agricultural Engineering

GPS – How it worksGPS – How it worksGPS – How it worksGPS – How it works

Constellation of more than 24 satellites– Known positions (at any time)

– Each continuously transmits time and position data• Two frequencies (L1-1575.42MHz and L2-1227.6MHz)

– Each orbits twice per day

Ground receiver (Your GPS receiver)– Calculates Position and Time

• Times signal and calculates distance to each satellite received

• Triangulates Latitude and Longitude• Calculates time

Components of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” system

ElectronicControlUnit

GPSReceiver /Antenna

UserInterface

Light Bar

GPS Assisted Guidance System

Components of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” system

ElectronicControlUnit

GPSReceiver /Antenna

UserInterface

Light Bar

DataLogger

GPS Assisted Guidance Systemwith Mapping

Components of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” system

GPS Based Yield Monitorwith Mapping

ElectronicControlUnit

GPSReceiver /Antenna

UserInterface

DataLogger

Chip Card

Mass flowMeter

Components of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” system

GPS Based Yield Variable Rate Planter

ElectronicControlUnit

GPSReceiver /Antenna

UserInterface

DataLogger

Chip Card

PlanterDrive

Components of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” systemComponents of a “GPS” system

ElectronicControlUnit

GPSReceiver /Antenna

UserInterface

SteeringServoDevice

GPS Based Automatic Steering System

Components of an auto-steering systemComponents of an auto-steering systemComponents of an auto-steering systemComponents of an auto-steering system

User Interface

GPS Receiver and Antenna

Electronic Control

Unit

Steering Servo Device

Wiring harness

http://www.newholland.com/h4/products/products_series_detail.asp?Reg=NA&RL=ENNA&NavID=000001277003&series=000005423311

MidTech system configurationMidTech system configurationMidTech system configurationMidTech system configuration

Midwest Technologies IL

Differential GPSDifferential GPSDifferential GPSDifferential GPS

Differential GPS is required for guidance– Without differential corrections, precision is ± 100 ft.– With corrections ±3 ft, ±4”, ±0.3”

Method:– Nearby ground station at known position uses GPS to

determine errors in distance to satellites– Errors are sent to roving GPS units

Issues– Where do you get the correction signals?

• Coast Guard

• Omnistar

• Deere

• other

Differential GPS communications Differential GPS communications pathwayspathwaysDifferential GPS communications Differential GPS communications pathwayspathways

PRN 12

PRN 2

PRN 8

PRN 18

RoamingGPSReference

Station

Differential CorrectionPathway

Differential correction sourcesDifferential correction sourcesDifferential correction sourcesDifferential correction sources

Source Cost URL

Terrestrial differential correctionUSCG Beacon Free users.erols.com/dlwilson/gpswaas.htmUser provided ? Self

SBAS (Satellite based Augmentation System)Omnistar $800/yr www.omnistar.com/faq.htmlOmnistarHP $1500/yr www.omnistar.com/faq.htmlDeere Starfire1 $500/yr StarFireGlobalHighAccuracySystem.pdfDeere Starfire2 $800/yr StarFireGlobalHighAccuracySystem.pdfWAAS Free users.erols.com/dlwilson/gpswaas.htm

http://www.navcen.uscg.gov/dgps/coverage/CurrentCoverage.htm

Coast Guard Beacon CoverageCoast Guard Beacon CoverageCoast Guard Beacon CoverageCoast Guard Beacon Coverage

Deere Starfire™ SBASDeere Starfire™ SBASDeere Starfire™ SBASDeere Starfire™ SBAS

John Deere’s StarFire System: WADGPS for Precision AgricultureTenny Sharpe, Ron Hatch, NavCom Technology Inc.; Dr. Fred Nelson, John Deere & Co.

Agriculture GPS Type Comparison    

         

Performance Low Middle High Very High

Technology Low cost DGPS

DGPS Two Frequency DGPS

Real Time KinematicRTK GPS

Price $100 to 600 $600 to $3,000 $1,500 to 10000 $25,000 to $42,000

         

Differential Source

WAAS WAAS +C.G. Beacon + SBAS

WAAS +C. G. Beacon + HP SBAS

User Base StationHP SBAS

Static Accuracy 5’-12’ 1’-3’ 4”-10” 1”

         

Application Scouting Mapping / Guidance

Mapping / Guidance

Elevation mapping, Precision row operations

GPS Technology vs. PrecisionGPS Technology vs. Precision(New Holland IntelliSteer ™ )(New Holland IntelliSteer ™ )GPS Technology vs. PrecisionGPS Technology vs. Precision(New Holland IntelliSteer ™ )(New Holland IntelliSteer ™ )

1. DGPS– Differential correction signal provided by free WAAS service.– Typical accuracy: +/- 10 inches

2. DGPS VBS (Virtual Base Station)– Differential correction signal provided by OmniSTAR subscription.– Typical accuracy: +/- 10 inches

3. DGPS HP (High Performance)– Differential correction signal provided by OmniSTAR™ subscription.– Typical accuracy: +/- 4 inches

4. RTK (Real Time Kinematics)– Differential correction signal provided by base station.– Typical accuracy: +/- 1 inch

http://www.newholland.com/h4/products/products_series_detail.asp?Reg=NA&RL=ENNA&NavID=000001277003&series=000005423311

Equipment on the marketEquipment on the marketEquipment on the marketEquipment on the market

M. Sullivan, Ohio State Univ.

GPS Receiver TypesGPS Receiver TypesGPS Receiver TypesGPS Receiver Types

Low cost GPS– Example: Handheld GPS

– Receiver Channels – 12– Position update rate 1 per 5 sec.– Likely to provide WAAS differential– Precision probably not better than ~ 5’– Data output may or may not have NMEA 0183 output

Mapping quality GPS (Simple DGPS)– Example: Trimble AgGPS 132

– Receiver channels – 12– US GPS/EGNOS capability– Position update 10 per second– WAAS, C. G. Beacon, Omnistar/Racal SBAS– Precision better than 3 ft– Data Output, NMEA 0183 + CAN

GPS Receiver typesGPS Receiver typesGPS Receiver typesGPS Receiver types

High Precision differential GPS– Example Deere Starfire-2

– Receiver channels 20 GPS, 2 SBAS both L1, L2 freq.

– US GPS/EGNOS capability

– Position update 5 to 50 per second

– WAAS, Deere SBAS

– Precision better pass to pass 4”

– Data Output, NMEA 0183 + CAN

– Slope compensation

GPS Receiver typesGPS Receiver typesGPS Receiver typesGPS Receiver types

RTK GPS– Example: Trimble Ag GPS 252

– Receiver channels – 24

– US GPS/EGNOS capability

– Position update to 10 per second

– WAAS, OmnistarHP, RTK

– Pass to pass accuracy 0.3” to 2”

– Data Output, NMEA 2000 ISO 11783 CAN

• Requires user provided base station– 2 x $8000 + $3000 lightbar + radio link

– Within 6 mi. radius line-of-site

Using Automatic SteeringUsing Automatic SteeringUsing Automatic SteeringUsing Automatic Steering

Easy to use – 15 min to learn– Enter field and move to start position.– Press “Start” or “A”– Drive the first pass– Press “Continue” or “B”– Turn to the next pass, System will lock on– Release the steering wheel or press “Resume”

Operating modesOperating modesOperating modesOperating modes

A

B

Parallel Linear Swathing

A

B

Curve following

Additional featuresAdditional featuresAdditional featuresAdditional features

Headland Indicator Return to Point Snap to Path Tilt Sensors

Return on investmentReturn on investmentReturn on investmentReturn on investment

Optimize Machine Efficiency (more acres with fewer hours)– Operate at faster field speeds– Reduce overlap

• Reduce per acre fuel consumption• Reduce overlap on implements and sprayers

Extend Machine Operating Time– Efficient night operation– Run in dust and fog

Reduce Operator Fatigue– More comfortable working hours– More time to supervize machine functions

Increase Yield– Manage compaction with planned traffic patterns– Place fertilizer and herbicides and pesticides more accurately

Automatic Steering may result in Automatic Steering may result in different farming practicesdifferent farming practicesAutomatic Steering may result in Automatic Steering may result in different farming practicesdifferent farming practices

Controlled compaction Tramlines Night operations Higher speeds

Midwest Technologies IL

Calculated returnsCalculated returnsCalculated returnsCalculated returns

Manual guidance allows a 13 percent increase in field speed while DGPS and RTK auto guidance allow a 20 percent increase. (Deboer and Watson, Purdue 1984)

Net revenues above variable and technology costs by $28 to $30 per acre (Watson, Purdue, 1983).

Impact of automatic guidance on an 1,800-acre corn/soybean farm (Lowenberg-DeBoer, Purdue 1984).

– Reduced field time by 17%, enabling the farm to expand while using the same machinery and increase returns by $7.36 per acre.

– If soils suffered moderate yield loss from compaction, the controlled-traffic capabilities of a high-accuracy guidance system could increase returns by $18.84 per acre.

Issues in selecting a GPS based Issues in selecting a GPS based guidance systemguidance systemIssues in selecting a GPS based Issues in selecting a GPS based guidance systemguidance system

Do’s– Assure system fits your vehicle(s)– Meets current and near term accuracy requirement– Is adequately portable for the need– Satisfies you on a test drive– Understand the differential correction requirements

• Subscription (SBAS)• Hardware (RTK)

– Compatible with other PF equipment you plan on using

ResourcesResourcesResourcesResources

Review of auto-steering systems– http://farmindustrynews.com/mag/farming_straightline_showdown/

Beelines link– http://www.beelinenavigator.com/

Trimble link– http://www.trimble.com/agriculture.shtml

Successful Farming (Richenburger)– http://www.findarticles.com/p/articles/mi_m1204/is_8_102/ai_n6178077