From GPS to GNSS Developments in Satellite Positioning Dr. Audrey Martin FSCS FRICS Lecturer Dept. of Spatial Information Sciences
1. Systems Developments GPS, Glonass, Galileo,... 2. Survey Methods Developments Static, Kinematic 3. Network Developments NRTK networks in Ireland 4. Hardware Developments & Future Trends
1. Systems Developments
GPS Modernisation 1978 Block I 1989 Block II (IIA IIR IIR-M IIF) 1995 Full Operational Capability 2000 Selective Availability discontinued 2005 2009 2014 Modernized GPS with a second civilian signal (L2C) 3 rd civil frequency with two codes (L5) Block III (GPSIII) New civilian signal (L1C)
L2C L5 SA Turned off http://adn.agi.com/satelliteoutagecalendar/sofcalendar.aspx
Frequencies GPS Signal Status More signals + more SV s = reduced measurement times
Glonass Developments 1992 2005 First Generation Block I SV prototypes. Block IIa 6 SV s launched. Block IIb 12 SV s launched Block IIV 25 Sv s launched. Second Generation 2007 14 Glonass-M SV s launched Total current SV s 23 2009 2010 Third Generation Glonass-K SV s 3 rd civil signal (L3) Operational 18 In commissioning phase 3 In maintenance 2
Current Glonass PDOP
Galileo Developments European Civilian GNSS 28 spacecraft orbital altitude: 23,222 km 3 orbital planes, 56 inclination, 2009 Two test t SV s GIOVE-A & GIOVE-B in orbit 2010 Surrey Satellite technology Ltd to build 14 SV s. 2014 Expected launch date of first 2 Galileo SV s
Average number of visible satellites (15 elevation cutoff angle) GPS WAAS Galileo EGNOS Glonass SDCM China Beidou RNSS - 2013 Compass GNSS 2015-2020 India RNSS GAGAN Japan: QZSS - 2010 MTSAT Satellite Space and Navigation Ground Systems Based Augmentation Systems In 2015 there will be up to 3 times the number of visible SVs and 4-6 times the number of individual signals
2. Survey Methods Developments
GNSS Accuracies Differential Autonomous Code Autonomous GNSS Carrier Phase Survey Grade GNSS DGNSS 10 mm 1 m 10 m 20 m
Carrier Phase Measurement Carrier Phase = Sinusoidal waves Number of wave-lengths measured ρ = nλ + θ + errors where: λ = known signal wavelength n = number of whole wavelengths θ = measured phase difference Ambiguity
Static Control Surveying The classical l method measurement To establish national & regional control Scientific studies Very high accuracy work - ±5mm over 100km. Rapid/Fast Static Densification of control points Measurement times 5mins + 1 min/km High accuracy work - ±5mm over 15km
Static Baselines Baselines B1 Cycle Slip Cycle B3 Slip B2 B4 B8 B5 4 Multipath Solution Type 15
Detail Surveying Stop and Go Feature points coded Post Processed for quality control Accuracy ±1-2 cm relative to the base. Kinematic (PPK) Surface Modelling Data collected at predefined intervals ` Accuracy ±1-2 2 cm relative to the base
Real Time Kinematic RTK Single Reference Station Advantages Straightforward principle Simple algorithm Traceability maintained Disadvantages Cost Time Short baseline length
RTK RTK Real Time Measurement OTF Initialisation Coordinate system of choice 2000 s 1990 s: radios, cables, power issues
3. Network Developments
Irish Network Developments 1995 IRENET95 National Passive Network 2001 ITM New GPS compatible Coordinate System 2002 OSi National Active Network (IRENET02) Continually Operating Reference Stations (CORS) RINEX data RTK Active Network for Dublin Irish Geoid Model OSGM02 2006 2007 Smartnet t Leica (OSi Active Network) VRSnow Ireland - Trimble 2010 TopNet Topcon (OSi Active Network) NRT K Additional service providers and services
Network (Modelled) NRTK NRTK correctional methods Virtual Reference Stations (VRS) Network Area Corrections (FKP) Master Auxiliary Concept (MAC) GNSS NRTK solutions require All ambiguities fixed Mixed mode fixing Correct data dissemination format
GB NRTK Accuracies No significant difference between commercial services (Leica & Trimble data streamed from OSGB) Accuracies attainable 10 20 mm in plan 15 35 mm in height Apply filters in real time greatly improves accuracy in challenging environments standard DOP filter is 6 below 3 is optimal Height differences greater than 250 m, between the rover and the base stations, may require additional measurements. www.tsa-uk.org.uk/
NRTK Accuracies in Ireland Smartnet Leica (OSI streamed data corrections) VRSnow Trimble (Trimble Infrastructure) 10 representative Passive IRENET stations selected Absolute & Relative NRTK accuracies compared IRENET Control
D137 Drogheda EASTING OSi SmartNet + Hiper Pro 776222.300 Service: OSi SmartNet Receiver: Hiper Pro D137 Drogheda OSi SmartNet + Hiper Pro 40 mm radius 776222.200 708560.100 708560.200 708560.300 708560.270 708560.220 708560.170 708560.120 1 100 199 298 397 496 595 694 793 892 991 1090 NORTHING OSi SmartNet t + Hiper Pro 776222.400 776222.350 776222.300 776222.250 776222.200 776222.150 776222.100 1 100 199 298 397 496 595 694 793 892 991 1090 35.850 ELEV. OSi SmartNet + Hiper Pro 35.800 35.750 35.700 35.650 35.600 1 78 155 232 309 386 463 540 617 694 771 848 925 100 107
D137 Drogheda Service: Trimble VRS Now Receiver: Trimble R8 708560.360 708560.340 708560.320 708560.300 708560.280 EASTING Trimble VRS + Trimble R8 D137 Drogheda VRS + Trimble R8 708560.260 708560.240 708560.220 1 149 297 445 593 741 889 1037 1185 1333 1481 1629 1777 1925 2073 2221 2369 2517 776221.900 40 mm radius 776221.900 NORTHING Trimble VRS + Trimble R8 776221.880 776221.880 776221.860 776221.840 776221.860 776221.820 776221.800 776221.840 776221.780 1 149 297 445 593 741 889 1037 1185 1333 1481 1629 1777 1925 2073 2221 2369 2517 776221.820 35.800 ELEV Trimble VRS + Trimble R8 35.780 776221.800 35.760 35.740 35.720 776221.780 35.700 35.680 708560.270 708560.290 708560.310 708560.330 35.660 1 136 271 406 541 676 811 946 1081 1216 1351 1486 1621 1756 1891 2026 2161 2296 2431 2566
Additional Developments
Hardware Firmware Software Receivers Integrated GNSS receivers. Improvements in atmospheric modelling techniques Antenna Design Multipath mitigation Increased sensitivity (Signal Noise Ratio) Bluetooth & Battery improvements Software/Firmware GNSS mixed mode processing New algorithms for atmospheric effects Use of narrow and wide lane signal processing 27
Multiband Receivers Future Trends Increased signal strength & robustness GNSS growth 200 100 0 Billion$ 2001 1 2020 2 New mass markets in person navigation and telematics Indoor GNSS Inertial systems coupled with high sensitivity GNSS receivers New buisness models - Client-server architecture Rovers receiver corrected coordinates in the field. Computational effort on the side of the server Data service brokers similar to mobile phone services