Transcript Slide 1

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?

Trilateration: The process of determining absolute or relative locations of points by measurement of distances, using the geometry of circles or spheres

Can be accomplished using information from 3 separate satellites

How GPS Works

Okay, 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 Decatur Springfield Indianapolis

2D Trilateration Procedure

1. You know the location of 3 satellites 2. Given the distance you are from those 3 satellites 3. Draw a circle, center is the location of the satellite, radius is distance from satellite 4. Repeat for all satellites 5. 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

Receiver DGPS Site

RTK Differential Correction

Receiver Radio/Cell DGPS Site

Signal Interference

Earth’s Atmosphere Solid Structures Metal Electro-magnetic Fields

Common GNSS Uses

• • • • • •

Military (Weapons precision) Navigation (Civilian or Commercial) Surveying Drainage Design Topography Measurements Precision Agriculture

Precision Agriculture – Brief History 1983 1991 - 1999 Finding the market - (20 years) “Wandering in the Wilderness” 1999-2004 2005-2007 Guidance adoption balloons 2007-2009 Integrated Applications Reagan announces GPS will be free for civilian use Customers begin Yield Mapping Satellite based guidance show payback Guidance Prices Decline and Expand Platforms; increasing ROI GPS guidance ties location and machine controls for integrated business applications

Precision Agriculture – Brief History Autonomous applications Convergence 2010 - 2011 Autonomy 2011 - 2012 Actionable Information Focus on “on-farm” Connectivity System Worksite Assisting Operators Removing Operators Combining agronomic data and machine info to increase yields

Reasons for Adoption – NA/LA/EU Land

 More efficient and productive use of equipment

Labor

 More efficiency with lower skilled level of labor

Lewis, P., et al (1998), Issues, Indicators & Ideas, Longman, South Melbourne.

Input Costs

 Reduce in field and end field overlap

2008 Eurostat – Agriculture statistics Main Results 2006-2007

Gov’t Reg

 Manage business for better compliance

2009 USDA – NASS - August Sugar cane burning in Brazil

Reasons for Adoption Land

Map out land and soil productivity

Water

Determine optimum drainage and leveling

Point B Crop

Access to Market Information based upon Location

Point A Gov’t Policy

Real time knowledge of crop conditions and potential yield impact

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