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Introduction to GNSS. Outline. GNSS Basics Common Uses Precision Agriculture – Brief History NA/LA/EU Agriculture Applications for West Africa. What is GNSS?. GNSS (Global Navigation Satellite System) Satellite navigation System Accurately and precisely locate a point on Earth - PowerPoint PPT Presentation
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Introduction to GNSS
Outline• GNSS Basics
• Common Uses
• Precision Agriculture – Brief History NA/LA/EU
What is GNSS?• GNSS (Global Navigation Satellite System)– Satellite navigation System – Accurately and precisely locate a point on Earth
– US – GPS (Functional)– Russian – GLONASS (Functional)– European – Galileo (Non Functional)– Chinese – COMPASS (BeiDou-2) (Non Functional)– Indian Regional Navigation Satellite System –IRNSS
(Non Functional)
How does it Work?Each GPS satellite transmits data that indicates its location and the current time
Satellites can be used if they are in the sight of a receiver as long as they are 25⁰ or greater above the horizon
GPS receivers require unobstructed view of the sky and they only receive data, don’t transmit it
How does it Find Location?
• Can be accomplished using information from 3 separate satellites
Trilateration: The process of determining absolute or relative locations of points by measurement of distances, using the geometry of circles or spheres
How GPS WorksOkay, you’re lost, you have amnesia, and you have absolutely no idea where you are. You go up to someone, and like a good amnesiac you ask, “Where Am I?” This person tells you that you are 180 miles from Chicago. You say, sarcastically, “Wow, that’s some great information. Thanks Buddy.”
Chicago
We’re Getting Closer
You still have absolutely no idea where you are, so once again you go up to someone and ask, “Where Am I?” This person tells you that you’re 170 miles from Indianapolis. You just scratch your head, but then you start to remember what you learned in GPS class, and, with the US map in your pocket to guide you, you proceed.
Chicago
Indianapolis
Now We Know! You see a another smiling
face and ask “where am I” one more time. This time you get the reply “you are 150 miles from Quincy. The light pops on in your brain. It’s all clear now. You draw three circles extending in the radii of 180 miles from Chicago, 170 from Indianapolis, and 150 miles from Quincy. The circles intersect in Decatur! Aren’t you glad that you took this class?
Chicago
Indianapolis
Springfield
Decatur
2D Trilateration Procedure1. You know the location of 3 satellites2. Given the distance you are from those 3
satellites3. Draw a circle, center is the location of the
satellite, radius is distance from satellite4. Repeat for all satellites5. Your location is where the 3 circles intersect
Trilateration (continued)• In 3-D you can use 4 satellites (using spheres
opposed to circles) to locate a precise location and include elevation
• The more satellites that are in range the more accurate GPS can be, mathematical models are used by GPS units to determine best accuracy
Differential Correction
• Raw GNSS is accurate only ~ 5-10Meters
• Differential Corrections adjust for errors.– Satellite Based
• WAAS/EGNOS• Purchased
– Ground Based• Real Time Kinematics
Satellite Differential Correction
DGPS SiteReceiver
RTK Differential Correction
DGPS SiteRadio/CellReceiver
Earth’s Atmosphere
Solid Structures
Metal Electro-magnetic Fields
Signal Interference
Common GNSS Uses• Military (Weapons precision)• Navigation (Civilian or Commercial)• Surveying• Drainage Design• Topography Measurements• Precision Agriculture
Precision Agriculture – Brief History
Integrated Applications
Guidance adoption balloonsFinding the market - (20 years)“Wandering in the Wilderness”
1991 - 1999
Reagan announces GPS will be free for
civilian use
1983
Customers begin Yield Mapping
1999-2004
Satellite based guidance show payback
Guidance Prices Decline and Expand
Platforms; increasing ROI
2005-2007 2007-2009
GPS guidance ties location and machine controls for integrated business applications
Autonomous applicationsDigital Convergence
2010 - 2011
Focus on “on-farm” Connectivity
System Worksite
Assisting Operators
Removing Operators
Combining agronomic data and machine info
to increase yields
Autonomy Actionable Information
2011 - 2012
Precision Agriculture – Brief History
Reasons for Adoption – NA/LA/EU
Sugar cane burning in Brazil
2008 Eurostat – Agriculture statistics Main Results 2006-2007Lewis, P., et al (1998), Issues, Indicators & Ideas, Longman, South Melbourne.
2009 USDA– NASS - August
Land Labor
Gov’t RegInput Costs
More efficient and productive use of equipment More efficiency with lower skilled level of labor
Manage business for better compliance Reduce in field and end field overlap
Reasons for Adoption
Access to Market Information based upon Location
Land Water
Gov’t PolicyCrop
Map out land and soil productivity
Determine optimum drainage and leveling
Real time knowledge of crop conditions and potential yield impact
Point B
Point A
Other GPS Facts• GPS time is theoretically accurate to
about 14 nanoseconds• GPS systems have settled disputes
between land owners• GPS data has revealed that Mt. Everest
is getting taller!
Thank You