From GPS to GNSS. Developments in. Dr. Audrey Martin FSCS FRICS Lecturer Dept. of Spatial Information Sciences

Transcription

1 From GPS to GNSS Developments in Satellite Positioning Dr. Audrey Martin FSCS FRICS Lecturer Dept. of Spatial Information Sciences

2 1. Systems Developments GPS, Glonass, Galileo, Survey Methods Developments Static, Kinematic 3. Network Developments NRTK networks in Ireland 4. Hardware Developments & Future Trends

3 1. Systems Developments

4 GPS Modernisation 1978 Block I 1989 Block II (IIA IIR IIR-M IIF) 1995 Full Operational Capability 2000 Selective Availability discontinued Modernized GPS with a second civilian signal (L2C) 3 rd civil frequency with two codes (L5) Block III (GPSIII) New civilian signal (L1C)

5 L2C L5 SA Turned off

6 Frequencies GPS Signal Status More signals + more SV s = reduced measurement times

7 Glonass Developments 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 Glonass-M SV s launched Total current SV s Third Generation Glonass-K SV s 3 rd civil signal (L3) Operational 18 In commissioning phase 3 In maintenance 2

8 Current Glonass PDOP

9 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 Expected launch date of first 2 Galileo SV s

10 Average number of visible satellites (15 elevation cutoff angle) GPS WAAS Galileo EGNOS Glonass SDCM China Beidou RNSS Compass GNSS India RNSS GAGAN Japan: QZSS 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

11 2. Survey Methods Developments

12 GNSS Accuracies Differential Autonomous Code Autonomous GNSS Carrier Phase Survey Grade GNSS DGNSS 10 mm 1 m 10 m 20 m

13 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

14 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

15 Static Baselines Baselines B1 Cycle Slip Cycle B3 Slip B2 B4 B8 B5 4 Multipath Solution Type 15

16 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

17 Real Time Kinematic RTK Single Reference Station Advantages Straightforward principle Simple algorithm Traceability maintained Disadvantages Cost Time Short baseline length

18 RTK RTK Real Time Measurement OTF Initialisation Coordinate system of choice 2000 s 1990 s: radios, cables, power issues

19 3. Network Developments

20 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 OSGM Smartnet t Leica (OSi Active Network) VRSnow Ireland - Trimble 2010 TopNet Topcon (OSi Active Network) NRT K Additional service providers and services

21 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

22 GB NRTK Accuracies No significant difference between commercial services (Leica & Trimble data streamed from OSGB) Accuracies attainable mm in plan 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.

23 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

24 D137 Drogheda EASTING OSi SmartNet + Hiper Pro Service: OSi SmartNet Receiver: Hiper Pro D137 Drogheda OSi SmartNet + Hiper Pro 40 mm radius NORTHING OSi SmartNet t + Hiper Pro ELEV. OSi SmartNet + Hiper Pro

25 D137 Drogheda Service: Trimble VRS Now Receiver: Trimble R EASTING Trimble VRS + Trimble R8 D137 Drogheda VRS + Trimble R mm radius NORTHING Trimble VRS + Trimble R ELEV Trimble VRS + Trimble R

26 Additional Developments

27 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

28 Multiband Receivers Future Trends Increased signal strength & robustness GNSS growth Billion$ 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