Worldwide Situating Frameworks (GPS).


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a satellite-based route framework comprising of a system of 24 ... the GPS satellites, check their operational wellbeing and careful position in space. ...
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Worldwide Positioning Systems (GPS)

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When GPS goes amiss Globe and Mail, Oct 7 2010 http://sheepfilms.co.uk/2009/09/15/gps/

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Satellites dispatched 1989-1994 Initially intended to pinpoint areas and diminish regular citizen losses

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What is GPS ? The Global Positioning System … a satellite-based route framework comprising of a system of 24 circling satellites that transmit radio signs to GPS recipients. The framework comprise of 3 \'portions\': Space section Control Segment User fragment

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1. Space fragment: Satellite Constellation GPS is the US framework Russia has GLONASS Europe arranges Galileo (2014) 24 satellites at 20,000 km height, at 55 degree point to equator (Glonass = 65)

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2. Control portion: ground stations These 5 stations screen the GPS satellites, check their operational wellbeing and correct position in space. The expert ground station transmits adjustments for the satellite\'s ephemeris constants and clock counterbalances back to the satellites

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3. Client portion: GPS beneficiary and radio wires Handheld diversion grade units 5-15 m Resource grade units 1-5 m Survey grade units 1 cm

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Pre-GPS: Survey triangulation

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GPS Tri lat eration Distance = Time x (Speed = 300,000 km/sec) Atomic checks measure time in seconds to 10 decimal spots Code is transmitted numerous thousand times each second and incorporates Time: Which satellite it is XYZ organizes (ephemeris)

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4 satellites are required for exact area (3 if just 2D) 4 time estimations relate with 4 \'pseudo-reaches\' (separations)

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Process: 1. Satellite conveys signal/code e.g. at midnight (with date stamp) 2. GPS units gets code at midnight in addition to travel time (decimal seconds) 3. The deferral or slack when the GPS gets it is the sign\'s travel time. 4. GPS unit increases the time by the pace of light to decide how far the sign voyaged = how far you are starting there in space 5. Programming joins the >4 readings to create a ground area (with some level of blunder)

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What are the wellsprings of mistake? Mistakes (estimated) Ionosphere 4.0 meters Clock 2.1 m Ephemeris 2.1 m Troposphere 0.7 m Receiver 0.5 m Multipath 1.0 m Total 10.4 m

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Selective Availability The irregular blunder, added to GPS signals before 2000 up to 100 meters blunder by scrambling last 3 decimals Turned off May 1, 2000 at midnight No expectation to ever utilize it again

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May 3, 2000 – Selective Availability Off May 1, 2000 – Selective Availability on

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Uncorrected GPS ~10m Corrected (DGPS) ~1m Differential Correction

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Dilution of Precision PDOP < 8.0 satisfactory PDOP < 4.0 : fantastic DOP is a pointer of the nature of the geometry of the satellites High DOP (poor) Low DOP (great)

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Dilution of Precision – 15 Degree Mask Angle

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# of satellites

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GPS vertical exactness = ~ 2x even mistake GPS units may likewise have worked in gauge for statures

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Multipath: GPS is observable pathway

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High scope, E-W valleys

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Environmental Factors Generally, GPS is unaffected by climate Heavy rain can debilitate the sign Wet foliage affects more than dry foliage Humidity and Temperature – no impact Wind may have beneficial outcome under backwoods shelter

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Wide Area Augmentation System - WAAS EGNOS (European Geostationary Navigation Overlay Service) Network of 25 area based stations that send amendment information to the satellites which thus transfer this information to our handheld GPS units In great conditions can enhance precision to 2-4 m Almost all new GPS units sold are WAAS empowered WAAS enhances exactness by redressing for mistakes in the satellite\'s clock and circle, and for ionospheric mistakes.

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WAAS Ground Stations

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POR      #47    3F3        Pacific Ocean at 178.0°E@ AOR-W   #35    3F4        Pacific Ocean at 142.0°W@ PanAm   #48  Galaxy 15   Pacific Ocean at 133.0°W* Anik     #51    F1R        Pacific Ocean at 107.3°W* WAAS Satellites - Geostationary

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Recreation Grade:  hiking, sailing, chasing $100-500 No differential adjustment No Setting of veil edge No setting of PDOP accumulation values Tracks stand out recurrence or flag No capacity to dismiss multi-way estimations Resource/Mapping Grade :  sub-meter precision $5,000 – 10,000 - Differential revision – post preparing or constant - Setting cover points PDOP esteem gathering Ability to dismiss multi-way estimations Survey Grade:   cms exactness $20,000-50,000 All of above in addition to: Tracking two frequencies Types of GPS units and mistakes

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GPS applications

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GPS untamed life collars - screen developments to minimize clashes between unsurprising bears and erratic people

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Coast Mountains, Mt. Waddington

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Measuring Glacier thickness with GPS UNBC Ph.D understudy Matt Beedle measures changes in the ice sheet\'s rise because of ice liquefy and stream A month back, a shaft in the icy mass with just a couple of millimeters appearing at the top was currently presented to almost his stature. Utilizing GPS hardware that can quantify his rise on the icy mass inside a centimeter, Beedle could affirm that the thickness of the icy mass by then had dropped more than 1.5 meters during that time of August alone. Matt additionally ski\'s down the ice sheet gathering RTK (Real-time motor) information

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Galileo Positioning System European Space Agency (ESA) elective 30 satellites on 3 orbital planes 27 nations included Major postponements tormenting framework Fully operational by 2014 Compatible with GPS (U.S.) Clocks 10 times more precise than GPS tickers Other Satellite Systems GLONASS Russia\'s partner is the US Global Positioning System (GPS) 21 satellites on 3 orbital ways Magellan and Trimble offer units that can use GLONASS signals Moving towards similarity with US and EU frameworks

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Some GPS locales: www.garmin.com Geocaching BC beacons www.gpsdrawing.com

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