2/4/2020 GNSS 101 – ERA OF INTEGRATION Wisconsin Society of Land Surveyors Conference Wisconsin Dells, 2020 1 PRESENTATION OUTLINE A general overview of GNSS today GPS USA • Physical Layer • Data Layer Global GLONASS RUSSIA Navigation • Application Layers Satellite BEIDOU • Integrations Systems CHINA • Other Interesting GNSS Applications GALILEO EU 2 BEFORE WE GET STARTED A few abbreviations to learn ANTCAL Antenna Calibration Format GDOP Geometric diluation of precision PPS Precision positioning service ANTEX Antenna Exchange Format GEO Geostationary Earth orbit PRN Pseudo-random noise ARP Antenna Reference Point GLONASS Global'naya Navigatsionnaya Sputnikova Sistema QZSS Quasi-Zenith Satellite System AS Anti-Spoofing GNSS Global Navigation Satellite System RAIM Receiver Autonomous Integrity Monitoring ATOM Adaptive Transmission of Optimized Messages GPS Global Positioning System RINEX Receiver Independent Exchange AUSPOS Australian Positioning Service GRS Geodetic Reference System RMS Root Mean Square BDS Beidou Satellite System HDOP Horizontal dilution of precision RTCA Radio Technical Commission for Aeronautics BINEX Binary Exchange Format IGS International GNSS Service RTCM Radio Technical Commission for Maritime Services BKG Bundesamt für Kartographie und Geodäsie IGSO Inclined geo-synchronous orbit RTK Real-time kinematic BPSK Binary phase-shift keying IOV In-orbit validation RTX Satellite and IP delivered corrections by Trimble CDMA Code division multiple access IRNSS Indian Regional Navigation Satellite System SA Selective Availability CEP Circular Error Probable ITRF International Terrestrial Reference Frame SAASM Selective Availability Anti-Spoofing Module CMR Compacted Measurement Record LLH Latitude Longitude Height SBAS Satellite-based augmentation system COM Center of Mass MEO Medium Earth orbit SDCM System for Differential Corrections and Monitoring CORS Continuously Operating Reference Station MGEX Multi-GNSS Experiment SINEX Solution Independent Exchange DGNSS Differential GNSS MSAS Multi-Function Satellite Augmentation System SPS Standard Positioning Service DGPS Differential GPS NAD North American Datum SSR State Space Representation DIP Direct Internet Protocol NGS National Geodetic Survey SVN Satellite vehicle number ECEF Earth-centered Earth-fixed NMEA National Marine Electronics Association TDOP Time dilution of precision EGNOS European Geostationary Navigation Overlay Service NRCAN National Resources Canada TEC Total electron count EPSG European Petroleum Survey Group NSAS Nigerian Satellite Augmentation System UHF Ultra-high frequency ESA European Space Agency NTRIP Network Transport of RTK via Internet Protocol UNAVCO University NAVSTAR Consortium ESRI Environmental Systems Research Institute OPUS Online Positioning User Service UTM Universal Transverse Mercator FDMA Frequency division multiple access PCV Phase Center Variation VDOP Vertical dilution of precision FOC Full operational capability PDOP Position dilution of precision VHF Very-high frequency GAGAN GPS-aided GEO Augmented Navigation PNT Positioning, navigation and timing WAAS Wide Area Augmentation System GATBP Geoscience Australia Test Bed Project PPP Precise point positioning WGS World Geodetic System 3 1 2/4/2020 BEFORE WE GET STARTED Abbreviations reorganized Positioning Space Messaging Systems Organizational Communications Mathematics Domain Component ANTCAL AS ATOM BDSBAS BKG BPSK CEP ANTEX SA CMR EGNOS CORS CDMA RMS ARP FOC RTX GAGAN EPSG DIP GDOP ECEF GEO DGNSS GLONASS ESA FDMA HDOP LLH IGSO DGPS GNSS ESRI NTRIP PDOP PCV MEO NMEA GPS GATBP RAIM TDOP PNT IOV PPP IRNSS IGS SAASM VDOP PRN PPS BINEX MSAS MGEX UHF COM SVN SPS RINEX NSAS NGS VHF GRS TEC SINEX QZSS NRCAN NAD SBAS OPUS UTM SDCM SSR WGS WAAS UNAVCO 4 PHYSICAL LAYER Physical properties of GNSS 5 PHYSICAL LAYER What is GNSS? • Ground Segment • Space Component •Users 6 2 2/4/2020 PHYSICAL LAYER GNSS Players • Global Services • SBAS Regional Services • GPS ~ 30 satellites • WAAS – USA ~ 3 satellites • GLONASS ~ 23 satellites • EGNOS – EU ~ 3 satellites • GALILEO ~ 22 satellites • BDSBAS – China ~ 3 satellites • BEIDOU ~ 35 satellites • MSAS – Japan ~ 2 satellites • Orbital Regional Services • GAGAN – India ~ 2 satellites • QZSS – Japan ~ 4 satellites • SDCM – Russia ~ 3 satellites • IRNSS – India ~ 8 satellites At least 138 navigation satellites in space 7 PHYSICAL LAYER GNSS Update • GPS III* • SV01 and SV02 in space • SV03, SV04 and SV05 awaiting launch • SV07, SV08 and SV09 are on the assembly line SV06 undergoing testing and validation in vacuum chamber 8 PHYSICAL LAYER GNSS Status • Beidou • 49 satellites | 24 are BDS III • Inter-satellite link capabilities • New generation rubidium and hydrogen maser clocks • 27 satellites in Medium Earth Orbit • 5 satellites in Geostationary Orbit • 3 satellites are inclined Geostationary Orbit 9 3 2/4/2020 PHYSICAL LAYER GNSS Status • Galileo designed as a 24 satellite constellation in 3 circular MEO orbits • Open Service signals currently available • Search and Rescue Service currently available • When fully operational, three additional services will be available • Public Regulated (Government) • Safety of Life • Commercial (Professional) 10 PHYSICAL LAYER GNSS Status • Glonass launched its most recent "M" class satellite December 11, 2019 from the Plesetsk cosmodrome. A January 2020 launch is also planned • Glonass and Beidou sign agreement to cooperate on the "Peaceful use of GNSS BDS and Glonass" • Glonass focuses on users by maintaining continuous services and stable performance 11 PHYSICAL LAYER Frequency Summary Frequencies in MegaHertz 1176.450 1207.140 1227.600 1246.000 1278.750 1561.098 1575.420 1602.000 GPS L5 L2 L1 GLO L2 L1 GAL E5a E5b E6 E1 BDS E5 E2 QZSS L5 L2 L1 SBAS L1 12 4 2/4/2020 PHYSICAL LAYER Radio Signal Characteristics GPS L5 GPS L2 GPS L1 13 PHYSICAL LAYER Mission Planning as a learning tool • Allows visualization of the physical layer • https://www.gnssplanningonline.com/#/maps 14 PHYSICAL LAYER Mission Planning as a learning tool • Allows visualization of the physical layer • Wisconsin Dells, Wisconsin | January 29th, 2020 @ 12:20 PM 15 5 2/4/2020 PHYSICAL LAYER Mission Planning as a learning tool • Allows visualization of the physical layer • Sentosa Island, Singapore | January 29th, 2020 @ 12:20 PM 16 PHYSICAL LAYER Expanding User Segment • GNSS assisted approaches for airplanes (LPV) is replacing the single-legged ILS landing method • Autonomy explosion – planes, trains, automobiles, drone deliveries, automated tasks, safety of life • Accurate positioning via GNSS is now an assumption worldwide – global infrastructure 17 PHYSICAL LAYER GNSS Receivers and Satellite Tracking Technology • GPS and Glonass are not perceived to be good enough - BDS and Galileo are expected • Combined signals from multiple constellations and frequencies are called X-Signals • The International GNSS Service (IGS) is conducting a pilot project called MGEX (Multi-GNSS Experiment) to study the X-Signals 18 6 2/4/2020 PHYSICAL LAYER GNSS antennas vary Magellan 111406 L1 Offset – 6.01 cm (2.37”) • PCV = Phase Center Variation • ARP = Antenna Reference Point Spectra Epoch 35 L1 Offset – 9.97 cm (3.93”) 90° 90° Phase Center Phase Center 0° 0° Spectra SP60 Antenna Reference Point Antenna Reference Point L1 Offset – 5.05 cm (1.99”) Phase Meter Phase Meter +π +π 0.f λ 0.f λ -π -π Elevation Elevation Ashtech 111661 (Imaginary) Ideal Antenna Real Antenna Pattern L1 Offset – 5.72 cm (2.25”) 19 PHYSICAL LAYER Leap Seconds – IERS • Precise Time is TAI (International Atomic Time) • GNSS uses TAI • Imprecise Time is known as UT1 • Varies due to long-term slowdown in the Earth's rotation • Normal clocks use some offset of UTC time which is referenced to TAI • Leap seconds are announced by the IERS to align UT1 and UTC • The GPS epoch began at midnight, January 6, 1980 • At that time, TAI – UTC = -19 seconds • Today, TAI – UTC = -37 seconds • Thus, GPS time is offset from UTC by 18 seconds ((TAI – UTC) + 19) 1972 1980 1990 2000 2010 2020 20 PHYSICAL LAYER GPS Week Number Roll-Over (WNRO) • The GPS epoch began at midnight on the cusp between January 5 & 6, 1980 • GPS uses a 10-binary counter to represent the week number • Every 19.7 years, this counter reaches its limit and rolls back to zero • April 6, 2019 was the second WNRO event in the GPS epoch 21 7 2/4/2020 PHYSICAL LAYER Sky Occlusion – GNSS Needs Sky • At least 4 visible satellites are required to compute a 3D position 22 PHYSICAL LAYER Clock Technologies and Timing • NASA Deep Space Clocks • The first GPS-like clock designed for deep space • Will allow spacecraft to navigate themselves versus relying on directions from Earth • The mercury-ion clock loses one second every 10 million years https://m.phys.org/news/2019-08-nasa-deep-space-atomic-clock.html 23 PHYSICAL LAYER Spoofing and Jamming • "Protect yourself from Interference with the Spirent GSS900 Series" • "U.S. officials warn of Iranian threats to commercial vessels including GPS interference" * • "Modeling jammed and spoofed signals to protect critical systems" – Orolia Defense Systems • Jamming and spoofing are becoming more prevalent, not just for the military but also for consumers – Cast Navigation, LLC • Protecting PNT | Anti-jam receivers protect data, mitigate navigation warfare threats – GPSWorld cover story, December 2019 • As the threat of jamming and spoofing increases, the receiver industry will have to develop counter measures and mitigation strategies – Cyrelle Gernot, Syntony GNSS *https://nypost.com/2019/08/07/us-officials-warn-of-iranian-threats-to-commercial-vessels-including-gps-interference/