Vehicle guidance
From horses to GPS
Jorge Heraud and Arthur Lange
Trimble Navigation Ltd.
June 2009
The greatest challenge
 This generation of engineers and scientists will need
to solve the toughest of problems ever encountered
– Energy shortage, Food shortage, Fresh water shortage, Global
Warming
 “Today more than ever before, Science holds the key
to our survival as a planet and our security and
prosperity as a Nation” Barack Obama, Dec 20, 2008
 I will show you, how previous generations rose to
tough technical challenges
For today
 History of automatic steering
 Modern automatic steering
 Why GPS guidance so widely used
History of manual guidance as
seen through patents
1870 - row marker for single-row
horse powered plowing
1876 - Two-row corn planter
with row marking
1953 – Cabled double row marker
1963 – Cabled folding row marker
1921 – Looking through the tractor
1951 – Front mounted visual aid
1951 – Double hood mounted visual aid
1990 – Windshield and hood visual aid
1976 – Visual aid for implement guidance
1970 – Electronically marking system
1987 – Paper tissue marking system
Tissue paper roll
goes here
History of automatic guidance as
seen through patents
1885 – "Furrow pilot”
1914 – Improved furrow follower
1949 – Movable furrow follower
1941 – Spiral guidance
1970 – Safety stopping mechanism
1976 – Automatic system to steer
harvesters
1976 – Crop feelers using strain gauges
1996 – Rocking sensors boundary detection
1998 – Ultrasonic sensor boundary detection
Modern Automatic Steering
systems
GPS based systems are now the norm for
automatic steering
 Manual GPS started around 1995
 Automatic GPS started in 1997
– Hydraulic, steer-by-wire, CAN, electric motor
Why is GPS guidance so widely
used
GPS guidance doesn’t accumulate errors
Re-start
Skips
Overlaps
Prior pass guidance
Fixed pass guidance
Visual aides, row markers,
foam markers
GPS, strings when planting
orchards
Convenient embodied technology with a
quick payback
 Savings of 10%+ on skips and overlaps
– Just drive to get the savings

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
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
Operate at faster speeds, at night
Reduced fatigue, convenience
All field patterns
All terrains
Facilitates / enables new practices
– Strip till, band spraying, drip tape, stripintercropping
 Reduces need for additional on farm labor
– Performance not skill dependent
– “Grandpa is planting again”
GPS guidance enables precision
Ag
Automatic section control
Automatic section control minimizes overlap and slow down
Headland
Reaction time
Overlap
area
Overlap cut down
by 75%
Overlap
eliminated
Automatic section control
 Field NOT Using Air
clutches
 Field Using Air
Clutches
Ag Journey
Ag Journey
Ag Journey
Ag Journey
Ag Journey
Ag Journey
Value Proposition
Automated Guidance
Implement Guidance
Variable Rate
Overlap Switching
Data Transfer
12.0%
3.0%
7.3%
4.6%
?
Total Savings
>26.9%
26.9%
22.3%
15.0%
12.0%
Engineers working on Automatic Guidance and
Precision Agriculture have increased
productivity by 26.9% in the last 14 years
The Ag Engineering community is ready for the next
challenge
GPS and GNSS review
GPS
1. Atomic standards in satellites (4 needed)
2. Satellites
transmit
ranging signals
& orbit info
3. Position, velocity,
& time computed from
range measurements
and data message
Each SV transmits signals and data
that are received by the rover (user
equipment). This allows the rover to
measure the distance to each SV.
These are the ‘Pseudoranges’
In 3-=dimensions, it takes 4
Pseudoranges to calculate the
position since time at the rover is
also a variable.
A GPS receiver measures Position,
Time, and Velocity. The velocity
measurement is independent of the
position measurement and is based
on the Doppler.
Increasing GPS accuracy
Four or more satellites
viewed by two receivers
Base station - a high
performance GPS receiver
placed in a fixed location
whose position is
accurately known.
Rover adds error to its
measured position to
obtain the corrected position
Error data is sent to
rover with radio
Autonomous GPS = 2 meters
Differential GPS = 0.5 meters
RTK (5 SVs)
= 0.02 meters
The GPS measured
position is compared sec
by sec against the known
position, and an error
calculated.
This error is assumed to be
the same error at the rover,
and is sent to the rover as
a ‘differential correction’.
GPS Operational GPS Satellites
 Current Satellites:
– 25 IIA/IIRs:
 10 Final Clock*
 2 will be decommissioned Spring 09
– 6 IIR-Ms: (L2C)
 Launch planned Mar 09, Aug 09 (with L5 enabled)
 Future Satellites
– GPS Block IIF (L5)
 IIF-1 launch Oct 2009
– GPS III
 Launch 2014
 24 satellites by ~2021
GPS Modernization Benefits
 GPS IIR-M L2C (1227 MHz)
– Improved L2 signal measurement – slight improvement to
IONO measurements
 GPS IIF L5 (1185 MHz)
– Improved RTK Acquisition
– Improved DGPS accuracy
 Higher chipping (10^7)
 Better ionosphere modeling
– Increased Power Level
 Improved operation under canopy
 Better SNRs
 GPS III
– L1C designed for interoperability with other systems
(Galileo, for example)
GPS Accuracy and Solar Cycle
RTK Performance with low and high
Ionosphere disturbance
RTK Performance
20
2-D Position Accuracy (cm)
18
16
14
12
10
8
6
4
2
0
0
5
10
15
20
25
30
Distance from Reference Station (Km)
35
40
45
50
E-W vs. N-S Accuracy
Global Navigation Satellite System (GNSS)
 GPS
– Space Based Augmentation Systems (SBAS)
 WAAS, EGNOS, MSAS, GAGAN, GRAS, CDGPS
 OmniSTAR, Starfire

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GLONASS (Russia)
QZSS (Japan)
Compass (China)
Galileo (EU)
Augmentation Systems for increased accuracy
 Space Based Augmentation Systems (SBAS)
– WAAS - Wide Area Augmentation System (US)
– EGNOS - European Geo Stationary Navigation Overlay
System (EU)
– MSAS - MTSAT Satellite-Based Augmentation System
(Japan)
– GAGAN (GPS Aided GEO Augmented Navigation) India
– GRAS (Ground Regional Augmentation) AUS
– Canadian DGPS
– OmniSTAR XP/HP
– StarFire
Augmentation Systems for increased accuracy
 Ground Based Augmentation Systems
– NDGPS MF Beacons (sub-meter)
– HA-NDGPS MF Beacons (4 sites are now
transmitting) 10-20 cm service (similar to
OmniSTAR XP/HP)
– RTK Base Stations – local radio
transmitters
– RTK VRS Networks – internet and cell
phones
 Trimble Terrasat
 CORS (Continuously Operating Reference
Station)
U.S. GPS Augmentation Update
 Wide Area Augmentation System (WAAS)
– Expanding monitor stations into Canada and Mexico
– Two SVs at 135 and 138 for North America
– WAAS satellites provide L1 and L5 ranging
– WAAS provides DGPS corrections including IONO
modeling
 Nationwide Differential GPS (NDGPS)
– DOT’s Research and Innovative Technology
Administration, funding of NDGPS is still a concern
European Geostationary Navigation
Overlay Service (EGNOS)
 Status
– AOR-E (120) and IOR-W (126)
 Initial Operations
– ARTEMIS (124)
 Testing
 Recommended reading
– EGNOS for Professionals web site WWW.ESA.INT
Benefits of Additional GNSS
 Availability
– More Satellites mean better availability in difficult
environments (Land Leveling in the Mississippi
Delta)
– Some system upgrades will have stronger
signals
 Reliability
– More Satellites mean no outages even with
individual satellite failures
GLONASS – the Russian GPS
 Currently (January 13, 2009) 16 Operational
SVs
 Goal is to have a full constellation of 24 SVs
by 2010
GLONASS and RTK
 Using GLONASS SVs with RTK will help
– Initialization
 Less than 5 GPS SVs - having some GLONASS
SVs available will aid RTK initialization
– Positioning
 Less than 4 GPS SVs – having some GLONASS
SVs will aid positioning
– Improved VDOP
 Adding any GLONASS SVs will help to reduce
VDOP
Compass (Beidou)
 4 geostationary (now in place) and 30 medium
orbit (MEO) satellites for global coverage
 MEO launches starting early 2009

Goal mid-2010 to have 10 SVs
 The Chinese Government has announced free 10
meter accuracy access to all, however, the ICD
has not been published.
 There is a high probability that Compass will
become operational before Galileo
Galileo – EU GPS
 Milestones
– First SV launched 2005
– Operational target 2013
 Fee for service will compete with “Free GPS”
 Galileo will not be a factor in the Ag market for at
least 3 or 4 years
 Expect to see lots of “Galileo marketing” activity
for the next few years
 L1C to interoperate with GPS III SVs
Questions?
Art_Lange@Trimble.com
Jorge_Heraud@Trimble.com
WWW.Trimble.com