Hydrofest The Hydrographic Society in Scotland

Transcription

1 Hydrofest 2017 The Hydrographic Society in Scotland

2 POSITIONING SYSTEMS Eddie Milne

3 1. GNSS Positioning 2. Additional Sensors 3. Alternative Positioning 4. Bringing it altogether

4 GNSS = GPS + Glonass + Galileo + Beidou

5 Main Error Sources: Satellite Orbit ±2.5m Satellite Clock ±2m Ionosphere ±5m Troposphere ±0.5m Receiver Noise ±0.3m Multipath ±1m GNSS Horizontal Accuracies 95% Confidence (2σ): GNSS ~15 m

6 Apply calculated SV clock error correction to broadcast ephemeris value Removing the Errors - PPP Apply satellite orbit corrections to broadcast orbit position Iono error is calculated using dualfrequency mobile GPS hardware Y Dx Z Dz erroneous SV Position Tropo delays minimised using model plus residual error is estimated as part of the calculation process Measurement noise and multipath minimised using carrier phase observable

7 Main Error Sources: Satellite Orbit ±2.5m Satellite Clock ±2m Ionosphere ±5m Troposphere ±0.5m Receiver Noise ±0.3m Multipath ±1m GNSS Horizontal Accuracies 95% Confidence (2σ): PPP or IAR 5-20 cm Differential 1-4 m SBAS (e.g. EGNOS) <6 m GNSS ~15 m SBAS: Differential: PPP: IAR: Space Based Augmentation Service (Free) Pseudo Range Correction (Free and Commercial Augmentation Services) Precise Point Positioning (Commercial Augmentation Service) Integer Ambiguity Resolution (Commercial Augmentation Service)

8 Offshore Correction Service Correction Type Horizontal Accuracy (95%) Satellites Veripos Apex 5 PPP 5 cm GPS, Glonass, Galileo, Beidou, QZSS Veripos Ultra 2 PPP 10 cm GPS, Glonass Veripos Std 2 Differential 1 m GPS, Glonass CNav C 1 PPP 10 cm GPS CNav C 2 PPP 8 cm GPS, Glonass Fugro Starfix G4 PPP 10 cm GPS, Glonass, Galileo, Beidou, Fugro Starfix G2+ PPP + IAR 3 cm GPS, Glonass Fugro Starfix G2,XP2 PPP 10 cm GPS, Glonass Fugro Starfix HP IAR 10 cm GPS Others: Positioneering, Atlas, Various Land Services

9 GNSS Practical Considerations Work Location Site Conditions Antenna Placement Cable Run

10 Threats to GNSS In-Band Interference Re-radiating GNSS systems GNSS systems, Tracking Dish Systems, Doppler Speed Logs, Heading Sensors Out-Band Interference Communications, LRIT, V-SAT, Sat-C, Iridium Microwave data links Radar systems TV antenna amplifiers or transmitters Telemetry Systems (data or video) Intentional Interference Jamming Spoofing

11 QC Software

12 GNSS alone is not enough Vertical Grid North GNSS Antenna E, N Additional to GNSS you need: - Offsets measured by tape measure or total station - Heading - Usually also Pitch, Roll and Heave

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14 Spinning Mass Gyro Fibre Optic Gyro Ring Laser Gyro Hemispherical Resonator GNSS Vector Heading GNSS RTK heading Technology Accuracy 2σ Examples Remarks Gimballed spinning gyroscope 0.2 static * Laser interferometer measuring Sagnac effect in a fibre coil Laser resonance in a clockwise and anticlockwise beam Flexural resonance of dome moves with rotation 0.4 dynamic TSS Meridian Surveyor 0.2 * IXSEA Octans, CDL TOGS * CDL Mini RLG, Sonardyne Lodestar, Kearfott T16, T24 Also does Pitch, Roll, Heave Also does Pitch, Roll, Heave 0.2 * Sagem BlueNaute Also does Pitch, Relative GNSS positioning 0.6 ** Hemisphere V series Carrier Phase count between base and rover Heading Sensors 0.1 ** Trimble SPS361, Fugro, Cnav, Veripos * Depends on latitude ** Depends on baseline length Roll, Heave

15 Heading Sensors Practical Considerations Aligning the gyro with the local Y-axis (usually the vessel longitudinal axis) Alongside - Dual antenna GNSS RTK heading - Land surveying vessel bow and stern - Tape measurement to known quayside heading Offshore - Dual antenna GNSS RTK heading - Sextant measurement to known points e.g. platforms - Sunshot

16 Motion Sensors (Pitch, Roll, Heave) AHRS Attitude & Heading Reference System (~0.02 / 5 cm 2σ) Ixblue Octans Sonardyne Lodestar MEMS Pitch, Roll, Heave Sensors (~0.1 / 10 cm 2σ) TSS DMS-05 Kongsberg MRU-5 SBG Ekinox Combined GNSS and IMU Systems Applanix POS- MV Coda Octopus F180

17 GNSS / IMU Integration Deep Tracking Loop Parameters -Faster re-acquisition of satellites and convergence Tight Satellites Measurements -Can continue to provide constrained solution with only 2 satellites -Intelligent measurement selection Loose Position -Bridges outages in GNSS availability -Intelligently removes GNSS Position Jumps -Faster Output Rates

18 Relative Positioning Applications: - Rig Positioning alongside a Platform - Platform Installation - Seismic Streamer Tailbuoy Positioning - Dynamic Positioned vessel close to platform Methods: - Total Station - Relative GNSS - Fanbeam, Radascan

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21 Putting It All Together: Nav Software GNSS (PPP) Heading Pitch/Roll/Heave Geodetic Parameters X, Y, Z Offsets Calibrations (C-O) Vessel Graphics Background Files Planning Lines/Points Multi Purpose Nav Software: - EIVA NaviPac - QPS Qinsy - Fugro Starfix - Others: Hypack, NavView, legacy software Winfrog, Hydropro, 4DNav etc

22 Putting It All Together: Error Budget Example at 60 Latitude Standard Deviation (deg) * RMS error secant latitude so divided by cos(60) Offset (m) Standard Deviation (m) Variance (m 2 ) GPS position Offset measurements TSS Gyro Dynamic error 0.40* TSS Gyro Settling error 0.20* Gyro Cal error Total σ (68% conf) σ (95% conf) 0.88

23 Putting It All Together: Nav Software GNSS (PPP) Heading Pitch/Roll/Heave Geodetic Parameters X, Y, Z Offsets Calibrations (C-O) Vessel Graphics Background Files Planning Lines/Points Multi Purpose Nav Software: - EIVA NaviPac - QPS Qinsy - Fugro Starfix - Others: Hypack, NavView, legacy software Winfrog, Hydropro, etc And Other Sensors