GPS Receivers University of Manitoba University of Manitoba Recreation Services GPS Workshop. Recreation Services GPS Workshop.

What is GPS? GPS is the acronym for Global Positioning System. GPS consists of a series of satellites (24+) that transmit data that allow receivers on Earth to determine their location with great accuracy. Also included in this system are ground stations (5) that are used for detecting and updating errors. Generally we only think about the receivers and call those a GPS or GPS units.

The Short Story! GPS Receiver (Hand Held Unit) GPS Receiver (Hand Held Unit) Triangulation with at least 3 satellites & a good view of the sky (4 satellites needed for X, Y and Z coordinates) Triangulation with at least 3 satellites & a good view of the sky (4 satellites needed for X, Y and Z coordinates) How accurate? How accurate? –±10-20m (elevation ~ ±2x horizontal error) –0.5cm with additional equipment

Where You Are - Triangulation 1 satellite 1 satellite 2 satellites 2 satellites 3 satellites (Lat/Long 2D) 3 satellites (Lat/Long 2D) 4 satellites gives altitude 4 satellites gives altitude

Enhancements to Accuracy (WAAS) Wide Area Augmentation System Wide Area Augmentation System –Geo-stationary Satellites –~25 ground stations of known location (North America) –corrects for GPS signal errors caused by ionospheric disturbances, timing and satellite orbit errors –Improves accuracy to 3-5m –Limits Must have good view of sky Must have good view of sky Antenna/receiver must be powered all of the time. Antenna/receiver must be powered all of the time.

Enhancements to Accuracy (DGPS) Differential GPS involves the cooperation of two receivers, one that's stationary and another that's roving around making position measurements. The stationary receiver is the key. It ties all the satellite measurements into a true known position. Differential GPS involves the cooperation of two receivers, one that's stationary and another that's roving around making position measurements. The stationary receiver is the key. It ties all the satellite measurements into a true known position.

DGPS Accuracy 1-3 meter with U.S. Coast Guard signal 1-3 meter with U.S. Coast Guard signal 0.5 cm with local base station (used extensively in Westside farming) 0.5 cm with local base station (used extensively in Westside farming)

Limitations for Hiking Need to see the sky! Need to see the sky! –Trees, buildings, mountains, some car windshields, etc... Only indicates place not movement or direction Only indicates place not movement or direction –So how does it measure speed and direction? –Minimum speed ~1.5km/hour (some up to 4km/hour) Power Power –Bring extra batteries Cold/Winter Temperatures Cold/Winter Temperatures –Power –LCD Screen

Sources of Error (~10m) Measures (some receivers display) Measures (some receivers display) –DOP (dilution of precision) –EPE (Estimate Position Error) Minimize Error Minimize Error –Averaging –Better Satellite Config –Move to get better sky view –Re-orient receiver (patch/helix) –Wait –Wait ErrorValue Ionosphere4.0 meters Clock2.1 meters Ephemeris2.1 meters Troposphere0.7 meters Receiver0.5 meters Multipath1.0 meter Total10.4 meters

Of Datums and Coordinates Datum Datum –NAD27 (Canada), NAD83, WGS84 Co-ordinate Co-ordinate –Lat/Long (dd.dddd, dd°hh’mm.ss”) N49°52'10.11" W097°13'45.95" –UTM/UPS (Zone Easting Northing) 14U –MGRS (Zone GridRef Easting Northing) 14UPA

Some Terms WayPoint WayPoint Bearing Bearing Track (log) Track (log) Route Route

Cost: $100-50,000 Based mostly on the need for accuracy Based mostly on the need for accuracy

GPS Applications in Agriculture Determine field boundaries Determine field boundaries Crop scouting (maturation, weeds, pests) Crop scouting (maturation, weeds, pests) Soil testing Soil testing Tillage Tillage Spraying (pesticides, herbicides, fertilizers) Spraying (pesticides, herbicides, fertilizers) Yield monitoring Yield monitoring