Global Positioning Systems. OnStar Navigation System.

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Global Positioning Global Positioning Systems Systems

Transcript of Global Positioning Systems. OnStar Navigation System.

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Global Positioning SystemsGlobal Positioning Systems

                               

            

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OnStar Navigation System

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Terms to KnowTerms to Know

AntennaAntenna – Receives signal from satellites – Receives signal from satellites and differential source.and differential source.

Attribute Attribute – A characteristic that describes – A characteristic that describes a Feature. They can be thought of as a Feature. They can be thought of as questions which are asked about the questions which are asked about the Feature.Feature.

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TermsTerms

Channel Channel – Consists of the circuitry – Consists of the circuitry necessary to track the signal from a single necessary to track the signal from a single GPS satellite.GPS satellite.

Degree Degree – Unit of angular measurement – Unit of angular measurement used to measure latitude and longitude. used to measure latitude and longitude.

Department of Defense (DoD) Department of Defense (DoD) – Created – Created Global Positioning SystemGlobal Positioning System

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TermsTerms

Differential Correction (DGPS) Differential Correction (DGPS) – – Comparing GPS data collected in the field Comparing GPS data collected in the field to data at a known point. By collecting to data at a known point. By collecting data at a known point a correction factor data at a known point a correction factor can be determined and applied.can be determined and applied.

Dilution of Precision (DOP) Dilution of Precision (DOP) – Positions – Positions tagged with a higher DOP value have tagged with a higher DOP value have poorer accuracy than those with a lower poorer accuracy than those with a lower DOPDOP

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TermsTerms

Ephemeris Ephemeris – The predicted changes in – The predicted changes in the orbit of a satellite the orbit of a satellite

Ephemeris ErrorsEphemeris Errors – Errors that originate – Errors that originate in the data transmitted by a GPS satellite. in the data transmitted by a GPS satellite. Ephemeris errors are removed by Ephemeris errors are removed by differential correction.differential correction.

Feature Feature – The object which is being – The object which is being mapped for the use in a GIS system. mapped for the use in a GIS system. Features may be points, lines, or areas.Features may be points, lines, or areas.

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TermsTerms

Geographic Information System (GIS) – Geographic Information System (GIS) – A mapping system that combines A mapping system that combines positional data with descriptive information positional data with descriptive information to form a layered map.to form a layered map.

Global Positioning System (GPS) Global Positioning System (GPS) – A – A system providing precise location which is system providing precise location which is based on data transmitted from a based on data transmitted from a constellation of 24 satellites. constellation of 24 satellites.

Raw GPS signal is only accurate to 100 Raw GPS signal is only accurate to 100 meters. meters.

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TermsTermsLatitude Latitude – The angular distance north or – The angular distance north or

south of the equator measured by lines south of the equator measured by lines circling the earth parallel to the equator circling the earth parallel to the equator

Degrees from 0 to 90Degrees from 0 to 90Longitude Longitude – The angular distance east or – The angular distance east or

west of the prime meridian west of the prime meridian Measured by lines perpendicular to the Measured by lines perpendicular to the

parallels and converging at the poles parallels and converging at the poles 0 to 180 degrees0 to 180 degrees

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Lines of LatitudeLines of Latitude

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Lines of LongitudeLines of Longitude

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TermsTerms Minute Minute – Unit of angular measurement – Unit of angular measurement

subdivision of Degrees. Each degree is divided subdivision of Degrees. Each degree is divided into 60’ (minutes). into 60’ (minutes).

One minute of latitude anywhere on the earth One minute of latitude anywhere on the earth and one minute or longitude at the equator and one minute or longitude at the equator equals 1.15 miles or 1 nautical mile.equals 1.15 miles or 1 nautical mile.

Second Second – Unit of angular measurement – Unit of angular measurement subdivision of minutes. Each minute is divided subdivision of minutes. Each minute is divided into 60” (seconds). into 60” (seconds).

One second of latitude anywhere on the earth One second of latitude anywhere on the earth and one second of longitude at the equator is and one second of longitude at the equator is equal to 33.82 yards.equal to 33.82 yards.

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TermsTerms

Multi-path Multi-path – The interference to a signal that – The interference to a signal that has reached the receiver antenna by multiple has reached the receiver antenna by multiple paths. paths.

Usually caused by the signal being bounced or Usually caused by the signal being bounced or reflected. Signals from satellites low on the reflected. Signals from satellites low on the horizon will have high multi-path error.horizon will have high multi-path error.

PPrecision Farming recision Farming – Carefully tailoring soil and – Carefully tailoring soil and crop management to fit the different conditions crop management to fit the different conditions found in each field.found in each field.

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Precision Farming Yield MapPrecision Farming Yield Map

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TermsTerms

Pseudo range Pseudo range – An uncorrected – An uncorrected measurement of the distance between a measurement of the distance between a GPS satellite and a GPS receiverGPS satellite and a GPS receiver

Receiver Receiver – Hardware component needed – Hardware component needed to process signals received by antenna.to process signals received by antenna.

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Garmin GPS Handheld Garmin GPS Handheld ReceiverReceiver

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GPS receiversGPS receivers

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Satellite Constellation Satellite Constellation – The group of 24 GPS – The group of 24 GPS satellites from which data is used to determine a satellites from which data is used to determine a

position.position.

                      

                     

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TermsTerms

Select Availability (SA) Select Availability (SA) – Government-– Government-induced signal error.induced signal error.

SNR SNR – Signal to noise ratio. Measure of – Signal to noise ratio. Measure of signal quality.signal quality.

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TermsTerms

Spatial Data Spatial Data – Data pertaining to the – Data pertaining to the location, shape, and relationship among location, shape, and relationship among geographical features.geographical features.

Value Value – Descriptive information about a – Descriptive information about a Feature. Feature.

Variable Rate Technology (VRT) Variable Rate Technology (VRT) – – Instrument used for varying the rates of Instrument used for varying the rates of application of fertilizer, pesticides, and application of fertilizer, pesticides, and seed as one travels across a field.seed as one travels across a field.

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TermsTerms

Yield Monitoring Yield Monitoring – Regular intervals – Regular intervals where a harvested weight has been where a harvested weight has been obtained along with a GPS reading. A obtained along with a GPS reading. A display of the weights translated to display of the weights translated to bushels/acre or yield provides a yield map.bushels/acre or yield provides a yield map.

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Examples of Variable Rate Examples of Variable Rate TechnologyTechnology

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Harvesting with VRTHarvesting with VRT

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Variable Rate Anhydrous Variable Rate Anhydrous AmmoniaAmmonia

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Parallel TrackingParallel Tracking

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2004 Corn Yield Map2004 Corn Yield Map

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2003 Soybean Yield Map2003 Soybean Yield Map

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What is GPS?What is GPS?

GPS (Global Positioning System)GPS (Global Positioning System)Created by US Dept. of DefenseCreated by US Dept. of DefenseOperates 24 hrs/dayOperates 24 hrs/dayStarted in early 1980’sStarted in early 1980’sFully operational April 27, 1995Fully operational April 27, 199524 NAVSTAR satellites (Navigation with 24 NAVSTAR satellites (Navigation with

Satellite timing and ranging)Satellite timing and ranging)

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What is GPS?What is GPS?

Orbit 10,900 miles above earth surfaceOrbit 10,900 miles above earth surfaceEach orbits every 12 hoursEach orbits every 12 hours6 orbital paths, 4 satellites per path6 orbital paths, 4 satellites per pathAt least 4 satellites always visibleAt least 4 satellites always visibleTransmit radio waves which travel at a Transmit radio waves which travel at a

rate of 186,300 miles/sec. (speed of light)rate of 186,300 miles/sec. (speed of light)

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What are the Satellites Like?What are the Satellites Like?

Weight: 1900 lbs.Weight: 1900 lbs.Size: 17 feetSize: 17 feetPower: 80 watts – 480 wattsPower: 80 watts – 480 wattsSignal: Signal:

Send two signalsSend two signalsCivilian useCivilian useMilitary useMilitary use

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How are the Satellites Controlled?How are the Satellites Controlled?

The US Air Force controls SatellitesThe US Air Force controls SatellitesMain tracking station: Falcon Air Force BaseMain tracking station: Falcon Air Force Base

Colorado Springs, COColorado Springs, CO• 5 tracking stations around the Earth5 tracking stations around the Earth

Satellites are trackedSatellites are trackedNew orbits predictedNew orbits predictedClock errors modeledClock errors modeledThis data is uploaded to satellites to send to user’s This data is uploaded to satellites to send to user’s

receiver. This info is called the receiver. This info is called the almanacalmanac

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How do we Communicate with the How do we Communicate with the SatellitesSatellites

Basic Components RequiredBasic Components RequiredAntennaAntenna – Receives signal from satellites – Receives signal from satellites

Two required for certain differentially corrected Two required for certain differentially corrected systems (may be housed in one unit)systems (may be housed in one unit)

ReceiverReceiver – Processes information contained – Processes information contained in signalin signalThis information is refereed to as almanacThis information is refereed to as almanac

PDAPDA – Personal Decision Aid (ex. computer) – Personal Decision Aid (ex. computer)Includes software needed to visualize informationIncludes software needed to visualize information

Power SourcePower Source

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Factors Affecting GPS AccuracyFactors Affecting GPS Accuracy

Selective availabilitySelective availabilityTechnique used by the DoD to reduce Technique used by the DoD to reduce

accuracyaccuracySatellite clocksSatellite clocks

Each satellite has an atomic clock but they Each satellite has an atomic clock but they are not completely accurateare not completely accurate

An error of one millisecond would produce an An error of one millisecond would produce an error or 186 mileserror or 186 miles

Satellite orbitsSatellite orbitsOrbit changes due to gravitation from sun and Orbit changes due to gravitation from sun and

moon. Known as Ephemerismoon. Known as Ephemeris

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Continued…Continued…

Earth’s atmosphereEarth’s atmosphereSlows radio signalsSlows radio signalsOccurs mostly in ionosphereOccurs mostly in ionosphere (50 to 250 miles up) blanket of charged (50 to 250 miles up) blanket of charged

particlesparticlesAlso in troposphere – from water vaporAlso in troposphere – from water vapor

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Continued….

• Multi-path errors– Signal bounce off near objects

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Improving AccuracyImproving Accuracy

Differential CorrectionDifferential CorrectionUses a stationary station of a known locationUses a stationary station of a known locationThe base station calculates the pseudo range The base station calculates the pseudo range

and determines the amount of error of each and determines the amount of error of each measurement and then calculates the true measurement and then calculates the true distancedistance

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Applications In AgApplications In Ag

Soil samplingSoil samplingYield mapping Yield mapping Variable rate planting/fertilizer applicationVariable rate planting/fertilizer applicationWeather dataWeather dataProduction costsProduction costsVariable rate chemicalsVariable rate chemicalsField scoutingField scoutingOthers???Others???