Enabling RTK-like positioning offshore using the global VERIPOS GNSS network. Pieter Toor GNSS Technology Manager

Transcription

1 Enabling RTK-like positioning offshore using the global VERIPOS GNSS network Pieter Toor GNSS Technology Manager

2 Introduction PPP/RTK Positioning Techniques PPP-AR Technology Presentation Overview PPP-AR Service Performance PPP-AR Re-Convergence Example Applications

3 Introduction Surface positioning technology has evolved providing Positioning on a global basis Improved accuracy and reliability Precise Point Positioning (PPP) has been used since 2000 GPS, then added GLONASS Signals from BEIDOU, GALILEO, QZSS offer further benefits PPP with Ambiguity Resolution Better position accuracy Rapid Re-convergence

4 What do we do? Provide Augmentation services for GNSS globally delivered via Satellite and Internet Using a network of GNSS tracking stations Diverse Control centres 7 Global Satellite beams on Inmarsat Satellites Veripos Brand in Marine market segments TerraStar Brand in Land market segment Provide hardware and software and full turnkey service in the Marine market Partner with GNSS Manufacturers in the Land market

5 VERIPOS Infrastructure 80+ Tracking Stations 2x Control Centres Redundant servers 7x satellite beams Internet delivery of data

6 Illustration of VERIPOS positioning solution Communication satellites Transmit correction data from the NCCS to the vessels on 7 L-band Inmarsat satellites GPS or GLONASS satellites Provide global redundant coverage NCCs Combine input data with proprietary algorithms to remove satellite-based positioning errors Comm. links Transmit data to NCCs. Minimum two separate links Onboard hardware and software GNSS reference stations Receive positioning GNSS reference stations NCCs signals and correction data, Equipped with dual redundant Receive positioning data from Fully enabling secure and systems and back up power. multiple satellites allowing for redundant accurate operations Located for maximum coverage positioning correctional facilities. measures Provide 24/7 customer support

7 VERIPOS Augmentation Services All services delivered over 7 geostationary Inmarsat beams Provides redundant delivery over the globe to approximately ±75º Latitude Configuration of primary PPP services includes redundant data sources (Apex/Ultra) Accuracies of <5 cm (2σ) horizontal and 12 cm vertical. Globally. Standard Differential GNSS services used as fall back solutions during PPP convergence Solution GPS GLONASS <5cm <10cm <1m VERIPOS Network Apex 2 JPL Network = GPS+GLONASS Ultra 2 Standard 2 Apex Ultra = GPS Standard

8 Introduction PPP/RTK Positioning Techniques PPP-AR Technology Precise Point Positioning Techniques PPP-AR Service Performance PPP-AR Re-Convergence Example Applications

9 Precise Point Positioning: PPP and RTK (1) RTK offers - Local / Regional solution: available within an RTK network or near a base station cm positioning + Initialisation <1 minute PPP offers: + Global solution: no knowledge of network required by user cm positioning - anywhere - Initialisation ~20-30 minutes - Requires full re-initialisation after loss of data

10 Precise Point Positioning: PPP and RTK (2) PPP-AR offers + Global solution: no knowledge of network required by user + RTK-like accuracies: 2-3 cm positioning - Initialisation ~20-30 minutes + Fast (~seconds) re-initialisation after short loss of data PPP-RTK offers ~ Regional / Wide Area solution: some knowledge of network required by user cm positioning + Initialisation <1 minute + Fast (~seconds) re-initialisation after short loss of data

11 Precise Point Positioning: PPP and RTK (3) Summary: Technique Area Accuracy (Horizontal) PPP-RTK delivers RTK capability but in a different way Initialisation Reinitialisation RTK Local/Regional 1-2 cm <1 minute <1 minute PPP Global 5-8 cm ~20-30 minutes ~20-30 minutes PPP-AR Global 2-3 cm ~20-30 minutes <1 minute PPP-RTK Regional/ Wide Area 1-2 cm <1 minute <1 minute

12 From PPP to PPP-RTK: layers of data required by applications Layer 1: PPP: User receives global orbit & clock information Layer 2: PPP-AR: User also receives observation specific biases Layer 3: PPP-RTK: User also receives ionospheric and tropospheric corrections Sum of PPP-RTK parameters enables RTK-like positioning Layered concept is defined by RTCM standard Orbit + Clock + Biases + Ionosphere + Troposphere = Same information as RTK

13 From PPP to PPP-RTK: layers of data required by applications PPP-RTK uses State Space Representation of GNSS error sources Message concepts designed by RTCM GNSS service providers generally adopt proprietary messages to efficiently use costly satellite bandwidth (image source: IGS workshop, June 2014, Pasadena, US)

14 PPP-AR Technology

15 PPP-AR what is it? Extension to Precise Point Positioning (PPP-AR = PPP with Ambiguity Resolution ) Ambiguity Resolution requires additional bias parameters to be computed and broadcast Use with Orbit & Clock corrections already used in regular PPP Enables horizontal accuracy of a few cm Supports rapid re-convergence, in many cases instantaneously Satellite specific ionosphere delays used as constraints in AR process VERIPOS PPP-AR service broadcast begun on 2 nd December 2014 for final validation Actively being used in land market since March 2015 Integration and testing in marine environment ongoing

16 VERIPOS Infrastructure Improvements VERIPOS offers PPP and PPP-AR services, globally High accuracy requires advanced infrastructure Entire reference station network upgraded over 18 month period New receivers = better GNSS measurement quality New geodetic antennas = better GNSS measurement quality Ability to track all GNSS constellations Developed Improved Servers To improve Orbits & Clocks To enable PPP-AR capability

17 PPP-AR Service Data Enabling ambiguity resolution requires the following Satellite orbit corrections Satellite clock corrections Satellite hardware biases of code observations Satellite hardware biases of carrier phase observations Data estimated in real-time by the VERIPOS orbit and clock determination algorithms Code biases very stable Phase biases stable but occasionally need reset Due to SV observability in tracking network

18 Server Processing & Data Dissemination

19 PPP-AR Service Performance

20 Apex 2 (PPP) Service Performance (29 th Dec 2014) Aberdeen Monitor Site

21 PPP-AR Service Performance (29 th Dec 2014) Aberdeen Monitor Site

22 PPP-AR Accuracy & Stability Example Norwich Monitor Site 2D: 2 cm (95%) Norwich Monitor Site Height: 7 cm (95%)

23 Service Performance Over Time <5 cm 3 cm <12 cm 8 cm Aberdeen Monitor Site

24 PPP-AR Position Solution Global Service Monitoring

25 PPP-AR Re-Convergence

26 PPP-AR Position Re-Convergence Cold-start or initial convergence is similar for PPP and PPP-AR Any break in GNSS observations results in loss of position On re-acquisition of GNSS observations PPP solution is typically re-set and repeat cold-start process PPP-AR solution can instantaneously re-converge to previous position accuracy Fast re-convergence is achieved if satellite specific line-of-sight ionospheric delays are estimated at all times These delays are then applied after re-acquiring satellites as a constraint to fix the carrier phase ambiguities instantly

27 PPP and PPP-AR Dynamic Performance Dynamic trials in urban setting Testing on vehicle Positions compared against a truth system Post-processed INS-GNSS Tightly-coupled PPP-AR (red) re-converges much quicker than PPP (green)

28 Re-Convergence After 5-sec Outage 15-min 30-min Apex 2 PPP (f/w 6.510) Apex 2 PPP (f/w 6.600) PPP-AR (f/w 6.600) 95% error computed over 72 re-convergences 5-second break in data (full GNSS & correction signal outage) 72 hourly gaps PPP re-converges PPP-AR bridges gaps Static data Different firmware versions with improvements to Apex 2

29 Re-Convergence After 30-sec Outage 15-min 30-min Apex 2 PPP (f/w 6.510) Apex 2 PPP (f/w 6.600) PPP-AR (f/w 6.600) 30-second break in data (full GNSS & correction signal outage) PPP-AR bridges 30-sec gaps <10cm within a few seconds 95% error computed over 72 re-convergences

30 2 minute gaps PPP-AR no gap bridging PPP-AR with gap bridging Green is Float (PPP), Red is fixed (PPP-AR) solution

31 Conclusions PPP-AR has the following main benefits for users Improved final accuracy Final accuracy is achieved faster than with PPP Immediate recovery from short (minutes) of GNSS data outage Suitable for applications with GNSS signal masking Global solution Easy to use

32 Example Applications

33 Marine Applications that benefit from PPP-AR Improved accuracy: Dredging Survey & Construction Improved stability: DP Gap recovery: Masked environments Overhead cranes

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