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GPS ReceiversGPS Receivers

University of ManitobaUniversity of Manitoba

Recreation ServicesRecreation ServicesGPS Workshop.GPS Workshop.

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What is GPS?What is GPS?

GPS is the acronym forGPS is the acronym for

Global Positioning System.Global Positioning System.

GPS consists of a series ofGPS consists of a series ofsatellitessatellites (24+) that transmit data that allow(24+) that transmit data that allowreceiversreceivers on Earth to determine theiron Earth to determine theirlocation with great accuracy. Also included inlocation with great accuracy. Also included in

this system arethis system are ground stationsground stations (5) that are(5) that areused for detecting and updating errors.used for detecting and updating errors.Generally we only think about the receiversGenerally we only think about the receiversand call those a GPS or GPS units.and call those a GPS or GPS units.

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The Short Story!The Short Story!

GPS Receiver (Hand Held Unit)GPS Receiver (Hand Held Unit) Triangulation with at least 3 satellitesTriangulation with at least 3 satellites

& a good view of the sky (4 satellites& a good view of the sky (4 satellitesneeded for X, Y and Z coordinates)needed for X, Y and Z coordinates)

How accurate?How accurate? 1010--20m (elevation ~20m (elevation ~ 2x horizontal error)2x horizontal error)

0.5cm with additional equipment0.5cm with additional equipment

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Where You AreWhere You Are -- TriangulationTriangulation

1 satellite1 satellite

2 satellites2 satellites 3 satellites3 satellites(Lat/Long 2D)(Lat/Long 2D)

4 satellites4 satellitesgives altitudegives altitude

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Enhancements to Accuracy (WAAS)Enhancements to Accuracy (WAAS)

Wide Area Augmentation SystemWide Area Augmentation System GeoGeo--stationary Satellitesstationary Satellites

~25 ground stations of~25 ground stations of

known location (North America)known location (North America) corrects for GPS signal errors caused bycorrects for GPS signal errors caused by

ionospheric disturbances, timing andionospheric disturbances, timing andsatellite orbit errorssatellite orbit errors

Improves accuracy to 3Improves accuracy to 3--5m5m LimitsLimits

Must have good view of skyMust have good view of skyAntenna/receiver must be powered all of the time.Antenna/receiver must be powered all of the time.

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Enhancements to Accuracy (DGPS)Enhancements to Accuracy (DGPS)

Differential GPS involves the cooperation of two receivers,Differential GPS involves the cooperation of two receivers,one that's stationary and another that's roving aroundone that's stationary and another that's roving aroundmaking position measurements. The stationary receiver ismaking position measurements. The stationary receiver isthe key.the key. It ties all the satellite measurements into a trueIt ties all the satellite measurements into a true

known position.known position.

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DGPS AccuracyDGPS Accuracy

11--3 meter with U.S. Coast Guard signal3 meter with U.S. Coast Guard signal 0.5 cm with local base station (used0.5 cm with local base station (used

extensively in Westside farming)extensively in Westside farming)

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Limitations for HikingLimitations for Hiking Need to see the sky!Need to see the sky!

Trees, buildings, mountains, some car windshields,Trees, buildings, mountains, some car windshields,etc...etc...

Only indicates place not movement or directionOnly indicates place not movement or direction So how does it measure speed and direction?So how does it measure speed and direction? Minimum speed ~1.5km/hour (some up to 4km/hour)Minimum speed ~1.5km/hour (some up to 4km/hour)

PowerPower Bring extra batteriesBring extra batteries

Cold/Winter TemperaturesCold/Winter Temperatures PowerPower

LCD ScreenLCD Screen

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Sources of Error (~10m)Sources of Error (~10m)

MeasuresMeasures (some receivers display)(some receivers display) DOPDOP (dilution of precision)(dilution of precision)

EPEEPE (Estimate Position Error)(Estimate Position Error)

Minimize ErrorMinimize Error AveragingAveraging

Better Satellite ConfigBetter Satellite Config Move to get better skyMove to get better sky

viewview

ReRe--orient receiverorient receiver (patch/helix)(patch/helix)

WaitWait

Error Value

Ionosphere 4.0 meters

Clock 2.1 meters

Ephemeris 2.1 meters

Troposphere 0.7 meters

Receiver 0.5 metersMultipath 1.0 meter

Total 10.4 meters

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Of Datums and CoordinatesOf Datums and Coordinates

DatumDatum NAD27 (Canada), NAD83,NAD27 (Canada), NAD83, WGS84WGS84

CoCo--ordinateordinate Lat/Long (dd.dddd, ddLat/Long (dd.dddd, ddhhmm.ss)hhmm.ss)

N49N4952'10.11" W09752'10.11" W09713'45.95"13'45.95"

UTM/UPS (Zone Easting Northing)UTM/UPS (Zone Easting Northing)14U14U 627231627231 55256225525622

MGRS (Zone GridRef Easting Northing)MGRS (Zone GridRef Easting Northing)14U14U PAPA 2723127231 2562225622

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Some TermsSome Terms WayPointWayPoint

BearingBearing

Track (log)Track (log)

RouteRoute

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Cost: $100Cost: $100--50,00050,000

Based mostly on the need for accuracyBased mostly on the need for accuracy

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GPS Applications in AgricultureGPS Applications in Agriculture

Determine field boundariesDetermine field boundaries Crop scouting (maturation, weeds, pests)Crop scouting (maturation, weeds, pests) Soil testingSoil testing TillageTillage Spraying (pesticides, herbicides, fertilizers)Spraying (pesticides, herbicides, fertilizers)Yield monitoringYield monitoring