See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/294259374 M.Sc. Presentation on Ambiguity function method. Research · February 2016 DOI: 10.13140/RG.2.1.4347.6247 CITATIONS READS 0 319 1 author: Sahan Dandeniya University of Newcastle 3 PUBLICATIONS 0 CITATIONS SEE PROFILE All content following this page was uploaded by Sahan Dandeniya on 13 February 2016. The user has requested enhancement of the downloaded file.
ADVANCED STUDIES ON AMBIGUITY FUNCTION METHOD AND IM IMPLEMENTATION IN IN THE RTKLIB Master Thesis Sahan Dandeniya Referee : Prof. Dr.-Ing. Reiner Jager Co Referee : Prof. Dr.-Ing. Tilman Müller Supervised by : Dipl.-Ing. Julia Diekert Institute of Geomatics Karlsruhe University of Applied Sciences Germany January 2015
Outline • Introduction • Theoretical Back Ground • GPSLAB/RTKLIB overview • Results and Analysis • Conclusion • Future Work • Questions 1/16/2015 Master Thesis 2
Introduction • The key to GNSS positioning is ambiguity resolution • Losses of Lock (Cycle slip) ask new ambiguity resolution • Duration of ambiguity resolution is of particular importance 1/16/2015 Master Thesis 3
Cycle Slip Phases time t i t i+1 t i+2 Graphical representation of cycle slip 1/16/2015 Master Thesis 4
INTRODUCTION Problem Identification • Bullet III is a low-cost antenna while 3G+C is a Geodetice grade antenna • Need significant time span to fix the ambiguity • Lose the fixed solution soon Suggestion: Applicability of Ambiguity Function Method Reference: Jaeger, Reiner, Andreas Hoscislawski, and Julia Diekert (2014). \Smart Phone RTK and Mobile GIS" 1/16/2015 Master Thesis 5
Objectives • Implement the AFM algorithm in RTKLIB • Analyze the behavior of AFM through observations of: • Varying baseline lengths • Single vs dual frequencies • Different number of epochs/Satellites • Compare the solution of AFM-RTKLIB with the solution of AFM-GPSLAB and MLAMBDA-RTKLIB 1/16/2015 Master Thesis 6
Carrier - Phase 1/16/2015 Master Thesis 7
RELATIVE POSITIONING Why Phase measurements? • Code observation: dm precision • Phase observation: mm precision • But receiver-satellite geometry has to be changed considerably (long observation time) to solve the position with mm-cm accuracy • If DD observations are resolved to integer within short time, position can be solved with mm-cm accuracy 1/16/2015 Master Thesis 8
RELATIVE POSITIONING Precision code vs Phase observation Code observation Phase observation Both are from relative positioning Phase: Provided that the integer ambiguity is KNOWN Reference: Sandra Verhagen,” Carrier Phase Integer Ambiguity Resolution – Recent results and open issues “, 2010, Delft University of Technology . 1/16/2015 Master Thesis 9
Integer Estimation ‚float‘ Solution Integer map ‚Fixed‘ solution Estimate Estimate Estimate position and integer position carrier ambiguity (ambiguity fixed) ambiguity Validate Validate float integer solution ambiguity 1/16/2015 Master Thesis 10
Integer Estimation Ambiguities not fixed Ambiguities fixed Reference: Sandra Verhagen,” Carrier Phase Integer Ambiguity Resolution – Recent results and open issues “, 2010, Delft University of Technology . 1/16/2015 Master Thesis 11
Pseudo-range Model Reference: Gps-Rtklib-Seminor-1 1/16/2015 Master Thesis 12
PSEUDORANGE MODEL Further Improvements Pseudorange Modeling in ECEF and GNSS-time Light time correction – - Due to celestial object motion (satellite) during signal transmission - Can be solved iteratively based on GNSS time t i and orbit O j and good position of X r Reference: Prof. Reiner Jäger (2014) , „ GNSS/MEMS/MOEMS -Multisensor-Navigation ( NAVKA)“,Riga Technical University 1/16/2015 Master Thesis 13
PSEUDORANGE MODEL Further Improvements • Additional corrections – Sagnac effect (incorporate earth rotation effect to Geo. range) Relativistic effect (GPS:Up to 13 m on horizontal position and 20 m on vertical position/ GLONASS: include in GONASS clock parameters) Geo dynamic corrections (Earth Tide Correction, Ocean Loading, Earth Orientation) Sagnac Effect Complete model No Geo dynamics corrections added Satellite time offset 1/16/2015 Master Thesis 14
Phase Measurement Model = Phase obs. Reference: Prof. Reiner Jäger (2014) , „ GNSS/MEMS/MOEMS -Multisensor-Navigation ( NAVKA)“,Riga Technical University 1/16/2015 Master Thesis 15
GPSLAB • For viewing and processing GNSS data • Development – MATLAB 5/Windows • Examination of a baseline • absolute and relative GPS positioning (SPP/DGPS/CDGPS) • Uses broadcast ephemeris • Processing of static observed data • Short baselines, especially at the carrier phase evaluation Zebhauzer (2000) Technical University of Munich (IAPG). 1/16/2015 Master Thesis 17
GPSLAB Data Structure M files/data files/text files Reference: Zebhauser, B. (2000 ). Ein MatLab-Toolkit zur Analyse von GPS-Beobachtungen mit Modulen für die Ambiguity Function Methode". 1/16/2015 18
RTKLIB - overview • An open source program package for GNSS positioning • Distributed under BSD 2-clause license • Has been developed by T. Takasu since 2006 • Latest version 2.4.2 (official) and 2.4.3 (beta) • Portable library and useful positioning APPs • GUI APPs on Windows • CUI APPS on Linux http://www.rtklib.com https://github.com/tomojitakasu/RTKLIB 1/16/2015 Master Thesis 19
RTKLIB - overview Features • standard and precise positioning algorithms with: GPS, GLONASS, Galileo, QZSS, BeiDou and SBAS • GNSS for both real-time and post-processing: Single, DGPS/DGNSS, Kinematic, Static, Moving-Baseline, PPP • supports many standard formats and protocols for GNSS: RINEX, RTCM, BINEX, NTRIP, IONEX , sp3 • It provides many library functions and APIs for GNSS data processing 1/16/2015 Master Thesis 20
RTKLIB - overview Package Structure 1/16/2015 Master Thesis 21
RTKLIB - overview GUI/CUI APs on Windows Function GUI APs CUI APs Real-Time Positioning RTKNAVI RTKRCV Communication Server STRSVR STR2STR Post-Processing Analysis RTKPOST RNX2RTKP RINEX Converter RTKCONV CONVBIN Plot Solutions and Observation Data RTKPLOT - Downloader of GNSS Data RTKGET - NTRIP Browser SRCTBLBROWS - 1/16/2015 Master Thesis 22
RTKLIB - overview GUI Aps on Windows 1/16/2015 Master Thesis 23
RTKLIB - overview RTKLIB APIs • Matrix and vector functions • Time and string functions • Coordinate functions • Input/output functions • Positioning models • Atmosphere models • Antenna models • Geoid model/Datum transformation • RINEX functions…….etc. 1/16/2015 Master Thesis 24
RTKLIB - overview Portability • Programming Language - API, CUI AP : ANSI C (C 89) - GUI AP : C++ • Underlying Libraries - TCP/IP Stack : Standard socket or WINSOCK - Thread : WIN32 thread or POSIX (pthread) - GUI Widget : Borland VCL on Windows • Build Environment - CUI AP : GCC, MS VS, Borland c, ... - GUI AP : Embarcadero C++ (VCL from c++ builder) on Windows 1/16/2015 Master Thesis 25
RELATIVE POSITIONING Double Differencing • Eliminate receiver clock errors • Eliminate initial receiver phase offsets • DD phase ambiguity is an integer number 1 2 1 - 2 3 1/16/2015 Master Thesis 26
Ambiguity Resolution Reference: Sandra Verhagen,” Carrier Phase Integer Ambiguity Resolution – Recent results and open issues “, 2010, Delft University of Technology . Integer ambiguities are derived from stochastic observations Integer ambiguities are not deterministic but stochastic Input (Stochastic) Output (Stochastic) 1/16/2015 Master Thesis 27
Ambiguity Resolution Methods LAMBDA Method (Teunissen, PJG(1995)) • Most popular / practically at top level • Cycle-slip correction required Reference: P.Joosten, C. Tiberius (2002). “LAMBDA : FAQs". 1/16/2015 Master Thesis 28
Ambiguity Resolution Methods Ambiguity Function Method (AFM) (Remondi B, 1984) • Search in the 3-dimensional position space (Currently not popular) • Cycle slip invariant 1/16/2015 Master Thesis 29
Ambiguity Function Method Euler‘s -function Single difference phase model e Phasor Diagram Reference: http://commons.wikimedia.org/wiki/File:Euler%27s_formula.svg 1/16/2015 Master Thesis 30
AMBIGUITY FUNCTION METHOD Single difference of observations Calculated range difference 1/16/2015 Master Thesis 31
THEORETICAL BACKGROUND . Ambiguity Function Method (AFM) 1/16/2015 Master Thesis 32
Data set / Measurements • Laboratory for GNSS and Navigation at Karlsruhe University of Applied Sciences (HsKA) and near by IGS station KARL (Location – Pillars on rooftop of B building ) Pillars on rooftop of B building • Data set used in GPSLAB (Zebhauser 2000) 1/16/2015 Master Thesis 33
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