GPSGPS:Accuracy and Repeatability in Agy p y g

2009 EQIP Precision Agriculture Incentive Training2009 EQIP Precision Agriculture Incentive TrainingJanuary 13‐16, 2009

Shannon Huber Norwood

Multi County Extension AgentMulti‐County Extension Agent

hubersr@aces.edu

Precision Ag Team

What is GPS?What is GPS?

• GPS, or global positioning system, is a  constellation g p g yof 24 satellites orbiting 12,660 miles above the Earth that is used for determining latitude and longitude ( )(position)

• Triangulation of satellites allows location d t i tidetermination

• Orbit the Earth once every 12 hours

• Operated by the Department of Defense

Precision Ag Team

Errors and Correction EvaluationErrors and Correction EvaluationGPS Drift, RTK

0.5

1.0

(XTE

) (m

)

•Receiver Noise

-1.0

-0.5

0.0

Cro

ss T

rack

Err

or

GPS Drift, Dual Frequency

1.0

m)

•Receiver Noise

•Satellite Clock Drift

-0.5

0.0

0.5

ss T

rack

Err

or (X

TE) (

m

•Orbit Estimation Error

•Atmospheric Delay -1.0

Cro

s

GPS Drift, Single Frequency

0.0

0.5

1.0

1.5

Erro

r (X

TE) (

m) •Multipath

-1.5

-1.0

-0.5

Cro

ss T

rack

Precision Ag Team

Selection and Proper ImplementationDifferent GPS correction services to use

Available Correction ServicesAvailable Correction Services• Satellite‐based differential correction (wide‐area)

– WAAS ‐ freeCommercial services– Commercial services

• OmniSTAR – XP or HP• John Deere Starfire ‐ SF1 and SF2

L l A diff ti l ti• Local Area differential correction– US Coast Guard beacon – free

– RTK (+/‐ 1 to 2 inches over time)b• Use own base station

• CORS ‐ free• RTK Networks

)) ))) )

Precision Ag Team

Levels for EQIP Precision Ag IncentiveLevels for EQIP Precision Ag Incentive• Nutrient Management (590)• Base: Variable rate application of nutrients is made• Base: Variable‐rate application of nutrients is made based on fertilizer results from grid or zone sampling1. Base requirement with no guidance2. Base requirement + guidance with free correction 

(WAAS SF1 etc)(WAAS, SF1, etc)3. Base requirement + guidance with paid subscription 

(HP/XP, SF2, etc)4. Base requirement + RTK‐level guidance (traditional or 

CORS)

Precision Ag Team

Levels for EQIP Precision Ag IncentiveLevels for EQIP Precision Ag Incentive• Pest Management   (595)

li i d i h hi l i d i h• Pest application made with vehicle equipped with1. Guidance using free correction (WAAS, SF1, etc)

2 Guidance using free correction (WAAS SF1 etc) + swath2. Guidance using free correction (WAAS, SF1, etc) + swath control

3. Guidance with minimum accuracy of +/‐ 4” (HP/XP, SF2, y / ( / , ,RTK)

4. Guidance with minimum accuracy of +/‐ 4” (HP/XP, SF2, RTK) th t lRTK) + swath control

Precision Ag Team

Wide Area Augmentation System (WAAS)Wide Area Augmentation System (WAAS)

• Corrects for GPS signal errors caused by Atmospheric disturbances– Atmospheric disturbances

– Clock error– Satellite orbit

• Compatible with basic GPS signal• Compatible with basic GPS signal structure– Compatible with WAAS enabled units

Purchase of additional equipment is NOT– Purchase of additional equipment is NOT necessary

• Broadcast at 1575.42 MHz (same as L1)• 3 to 5 meter (free) improving• 3 to 5 meter (free) ‐ improving

Precision Ag Team

OmniStar and John Deere• Subscription services• Receiver must be compatible

O Sta a d Jo ee e

OmniStar– VBS – sub‐meter ($800 / year)

XP 20 ($800 / )– XP – 20 cm ($800 / year)– HP – 10 cm ($1500 / year)

John Deere Starfire System

Courtesy of Trimble

John Deere Starfire System– SF1 – Single frequency

• 1 meter (free) SF2 Dual frequency– SF2 – Dual frequency 

• 10 cm ($800 / year)

Courtesy of John Deere

Precision Ag Team

Real‐Time Kinematics (RTK)Real Time Kinematics (RTK)• Utilizes base station to transmit correction

– 6 mile limitation (line of sight)• Repeaters can extend distance

• Base station creation– Setup over a known survey point – If survey point unavailable

• Archive data for post‐processing• Setup at highest location• Setup at highest location

• Most accurate system available (1‐3 cm) • RTK is the only correction method that can 

provide repeatable centimeter horizontalprovide repeatable centimeter horizontal accuracy!

Precision Ag Team

RTK NetworksAllow for expanded operating range of RTK enabledrange of RTK enabled equipment.

Reduced investment cost for RTK applicationsRTK applications.

Prevent producers from dealing with maintenance and upkeep of base station equipment.

Subscription fee required

Courtesy of eGPS Solutions

Precision Ag Team

Continuously Operating Reference ( )Station (CORS)

– Coordinated by the National Geodetic Survey Coordinated by the National Geodetic Survey (NGS) of the National Oceanic and Atmospheric Administration (NOAA), Continuously Operating Reference Station (CORS) sites provide GPS measurements in

t f 3 di i l iti i ti itisupport of 3-dimensional positioning activities.– Real time data is available via radio or smart

phone; data is archived on line for 90 days for phone; data is archived on-line for 90 days for post-processing applications

Precision Ag Team

CORS BackgroundCORS Background• Traditional CORS Users

D t t f T t ti– Department of Transportation– Surveying Industry

• Used for what?– Subsidence

– Road construction

– Monitor water levels

– Crustal movement

Precision Ag Team

CORS and AgricultureCORS and Agriculture

• Traditionally base stations have been used toTraditionally, base stations have been used to obtain RTK level accuracy– Approximately 6 mile radius– Approximately 6‐mile radius 

• Base stations are line of sight

• Terrain can be limiting factor for base stations

• CORS  provides a larger coverage area– Approximately 20 mile radius

Precision Ag Team

Current AL CORS sites

Precision Ag Team

FutureFutureAL CORS Sites (green triangles)

Goals• Statewide CORS CoverageStatewide  CORS Coverage

• Establish VRS (Virtual Reference Station)

Precision Ag Team

Precision Ag Team

GPS Receiver Performance

Low-Cost Sub-Meter Sub-Foot RTK

$80-300 $1k – 4k $5k-10k >$25k

3 16 ft < 3 ft < 6 in < 1 in3-16 ft. < 3 ft. < 6 in. < 1 in.

< 10 in. ~ 6 in. < 6 in. < 3 in.

1 - 4 ft. < 2 ft. < 2 ft. < 3 in.

O i t HP N d BWAAS Various Omnistar HPStarfire2

Need Base Station

General Accuracy, Pass‐to‐pass Accuracy, Repeatability

Precision Ag Team

General Accuracy, Pass to pass Accuracy, Repeatability

Terrain CompensationRoll ExampleRoll Example

GPS Antenna

Roll AnglePosition without TC

Corrected position by TC

Precision Ag Team

New / Future for GPSNew / Future for GPS• GNSS

– GPS + GLONASS + Galileo– Improve solution stability– Increased accuracy?

• L2C Signal– 2nd civilian signalg– Improve solution accuracy

• L5 – 3rd civilian signalg• L1C – 4th civilian signal (upgrade to L1 C/A)

Precision Ag Team

Guidance

2009 EQIP Precision Agriculture Incentive Training2009 EQIP Precision Agriculture Incentive TrainingJanuary 13‐16, 2009

Shannon Huber Norwood

Multi County Extension AgentMulti‐County Extension Agent

hubersr@aces.edu

Precision Ag Team

Guidance Usageg• Planting 

• Sprayingp y g

• Spreader/applicators

• Tillage• Tillage

• Harvesting

Precision Ag Team

Guidance BenefitsGuidance Benefits• Extends operational hours –

operate at night

• Minimizes driver fatigue

• Improves field efficiency: eliminates guess rows, i i i ki d lminimizes skips and overlap

– Minimize driver errors

Reduce overlap on implements– Reduce overlap on implements and sprayers

Precision Ag Team

Maintain parallel passes Planting is critical since it establishes crop rows for the entire season.

Maximize field usage

Marriage Rows

Precision Ag Team

Non‐parallel rowsAdditional 12‐rows could have been planted

Sprayers – 60,  90 and 120 ft  widthMinimize overlapMinimize overlapImprove field efficiency

Precision Ag Team

Conservation Tillage Practices• Minimize guess work• Improved field efficiency

Precision Ag Team

• Improved field efficiency

Strip Tillagep gPermits…

• Reduced soil compaction

Precision Ag Team

• Reduced field preparation costs (less energy)• Quicker soil warm‐up times.

Non‐uniform cotton standIncorrect cotton row placement over SDI tapeVariability from row‐to‐row

Precision Ag Team

Ability to work accurately at nightCourtesy of John Deere

Precision Ag Team

Types of GuidanceTypes of Guidance2 Types of Systems:1 Li htb P ll l T ki1. Lightbar or Parallel Tracking

– Operator still drives machine Li htb id f db k – Lightbar provides feedback on proper positioning reference

2 Autoguidance or AutoSteer2. Autoguidance or AutoSteer– Machine drives itself– Operator only turns machine around then – Operator only turns machine around, then

lines up on next pass before engaging**

Precision Ag Team

LightbarsLightbarsSimpleFairly preciseReliableEconomical

Courtesy of John Deere, Mid‐Tech, Raven, and Trimble

Precision Ag Team

Autosteering TechnologyAutosteering Technology• Electronic controls override

standard steering valvesstandard steering valves.• Steering decisions are made

via initial driver input (AB line via initial driver input (AB line establishment) and GPS position information.

• Electronic processor unit calculates precise steering

l d d angle and passes command along to the steering valve.

Precision Ag Team

RTK TechnologyRTK Technologycorrection signal

Base station corrects GPS signal based on its known 

locations.

Base station sends corrected GPS signal via radio or cell phone to rover unit mounted on tractor

Precision Ag Team

CORS Set‐upCORS Set upCorrection data is

Phone/modem connects todata is 

placed on the internet.  

connects to internet to receive 

correction.

CORS Station

Precision Ag Team

CORS Correction SignalCORS Correction Signal

• Good cell phone coverage the smart phoneGood cell phone coverage…the smart phone or modem dials into an IP address and then delivers the correction signal to the auto‐delivers the correction signal to the autoguidance equipment

Precision Ag Team

CORS Correction SignalCORS Correction Signal

• Good cell phone coverage the smart phoneGood cell phone coverage…the smart phone or modem dials into an IP address and then delivers the correction signal to the auto‐delivers the correction signal to the autoguidance equipment

• Not all brands of auto guidance accept the• Not all brands of auto‐guidance accept the correction signal…we are hoping that more manufacturers will allow their equipment tomanufacturers will allow their equipment to access CORS.

Precision Ag Team

AutoSteer ClassesAutoSteer Classes• Large Sprayers

$8 500 $20k – $8,500 - $20k

Precision Ag Team

AutoSteer ClassesAutoSteer Classes• Chemical &fertilizer application

Sub foot – Sub-foot – $15k - $25k

L S• Large Sprayers– $8,500 - $20k

Precision Ag Team

AutoSteer ClassesAutoSteer Classes• Tillage, drilling, planting

RTK – RTK – $28k - $40k – Planting cultivation multiple operations – Planting, cultivation, multiple operations

• Chemical &fertilizer application – Sub-foot Sub foot – $15k - $25k

• Large SprayersLarge Sprayers– $8,500 - $20k

Precision Ag Team

AutoSteer ClassesAutoSteer Classes• Tillage, drilling, planting

– RTK– $28k - $40k – Planting, cultivation,

multiple operations multiple operations • Chemical &fertilizer application

– Sub-foot – $15k - $25k

• Large SprayersS b f t– Sub-foot

– $8,500 - $20k

Precision Ag Team

Guidance CostsGuidance Costs

Entry level guidance system ~$1800

Guidance with subscription correction service and assisted steering ~$6500

RTK guidance (including base)  ~$45,000

Precision Ag Team

Guidance CostsGuidance Costs

Entry level guidance system ~$1800

Guidance with subscription correction service and assisted steering ~$6500

RTK guidance (including base)  ~$45,000

Precision Ag Team

Guidance BenefitsGuidance Benefits• Reduce per acre fuel consumption • Operate at faster field speeds• Cover more acres with fewer hours of operation

C ll d ffi• Controlled traffic patterns• More accurate placement of agronomic inputs 

such as fertilizer and herbicidessuch as fertilizer and herbicides

Precision Ag Team

Levels for EQIP Precision Ag IncentiveLevels for EQIP Precision Ag Incentive• Nutrient Management (590)• Base: Variable rate application of nutrients is made• Base: Variable‐rate application of nutrients is made based on fertilizer results from grid or zone sampling1. Base requirement with no guidance2. Base requirement + guidance with free correction 

(WAAS SF1 etc)(WAAS, SF1, etc)3. Base requirement + guidance with paid subscription 

(HP/XP, SF2, etc)4. Base requirement + RTK‐level guidance (traditional or 

CORS)

Precision Ag Team

Levels for EQIP Precision Ag IncentiveLevels for EQIP Precision Ag Incentive• Pest Management   (595)

li i d i h hi l i d i h• Pest application made with vehicle equipped with1. Guidance using free correction (WAAS, SF1, etc)

2 Guidance using free correction (WAAS SF1 etc) + swath2. Guidance using free correction (WAAS, SF1, etc) + swath control

3. Guidance with minimum accuracy of +/‐ 4” (HP/XP, SF2, y / ( / , ,RTK)

4. Guidance with minimum accuracy of +/‐ 4” (HP/XP, SF2, RTK) th t lRTK) + swath control

Precision Ag Team

Questions?Questions?

Precision Ag Team