Gnss Technologies

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GNSS Technologies Next Generation GNSS 18.1.2016 Dr. Zahidul Bhuiyan Finnish Geospatial Research Institute, National Land Survey Content Global Navigation Satellite Systems GNSS Evolution Multi-GNSS Advantages GNSS receiver basics GNSS Modulations Signal Characteristics Galileo Services Multi-GNSS Challenges A practical example of multi-GNSS Summary           2 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Accuracy around 5 m with consumer-grade devices (code) and centimeter-level with professional devices and reference networks (phase) Satellite locations are known Signal travel time or number of carrier phase cycles => range 3 GNSS Technologies • GNSS signal consists of multiple components • Carrier phase, code, data Position, Velocity, Time • Low-cost consumer receivers use only code-based range for positioning • Carrier phase observations and reference networks enable higher accuracy 18.1.2016 [email protected], [email protected], [email protected] Global Navigation Satellite Systems Existing and future GNSS:  Global Constellations      4 GPS GLONASS Galileo* BeiDou*  Satellite-Based Augmentations     WAAS EGNOS MSAS* GAGAN* Regional Constellations  QZSS*  IRNSS* GNSS Technologies *Future 18.1.2016 [email protected], [email protected], [email protected] Current Status of Multi-GNSS GPS GALILEO GLONASS BeiDou First launch 1978 2011 1982 2007 Full Operational Capability (FOC) 1995 2018~2020 2011 2020 Number of planned satellites 30 30 24 35 Current Status 30 operational, 1 under maintenance, 1 under commissioning 8 operational, 2 under maintenance 23 operational, 2 in preparation, 2 in flight tests phase 14 operational satellites, 4 under commissioning Orbital planes 6 3 3 3 Access Scheme CDMA CDMA FDMA/CDMA CDMA  SBAS: 3 WAAS, 3 EGNOS, 3 SDCM, 4 IRNSS (7 planned), 1 QZSS (7 planned) 5 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Next generation GNSS (1/2) GPS F r e q u e n c i e s GLONASS Galileo Compass/ BeiDou Japanese QZSS Source: Stefan Wallner Indian IRNSS 6 GNSS Technologies E5/L5 band L2 band E6 band E1/L1 band 18.1.2016 [email protected], [email protected], [email protected] Next generation GNSS (2/2)  Position Dilution of Precision (DOP) with multi-GNSS Multi-GNSS leads to improved availability and accuracy Source: Manuel Toledo Lopéz, GMV 7 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] The US GPS (1/3) GPS      8 The American GPS consists of a nominal constellation of 24 BLOCK ll satellites and three active spares and their ground base stations The GPS BLOCK ll satellites orbit the Earth once every 12 hours on six orbital planes angled 55° from the equatorial plane Life expectancy of these satellites is 7.5 years Ground station locations are: Hawaii, Ascension Island, Diego Garcia, Kwajalein, and Colorado Springs GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] The US GPS (2/3) GPS had its full operational constellation declared in 1995 Intentional signal degradation SA (selective availability) was turned off in 2000 Only L1 and L2 frequencies until 2009 when L5 was added The GPS signals are generated in the satellites by utilizing a common atomically stabilized clock operating at 10.23 MHz      L1 154*10.23 MHz   L2 120*10.23 MHz   9 P and C/A codes P code and C/A in the future L5 115*10.23 MHz GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] The US GPS (3/3)  The GPS constellation is very robust   30 space vehicles currently in operation Projected future: 30 BLOCK III satellites with modernized signals 10 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] The Russian GLONASS  GLONASS  The Russian GLONASS FDMA system consists of a nominal constellation of 24 (21 active and 3 spares) KOSMOS satellites and their ground base stations  The KOSMOS satellites orbit the Earth once every 11 hours and 15 minutes on three orbital planes separated by 120° and with orbits inclined 65 degrees  Life expectancy of these satellites is 3-5 years  Next generation satellites are being developed with an expected service life of 10 years and CDMA technology  All ground base stations are located within former Soviet Union territory  GLONASS uses a different geocentric datum (PZ-90)  GLONASS time and GPS time are not the same  Projected future: 24 CDMA satellites by 2020 11 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] The European Galileo  Galileo     The European Union Galileo will consist of a constellation of 30 GSTB-V2 satellites (27 active and 3 spares) and their ground base stations The GSTB-V2 satellites orbit the Earth once every 14 hours on three orbital planes angled 56° from the equatorial plane Life expectancy of the satellites is yet to be determined Ground base stations will be located throughout Europe   12 two Galileo Ground Control Centres in Oberpfaffenhofen (GER) and Fucino (IT) have been inaugurated Full FOC-1 infrastructure in orbit, comprising 8 operational satellites GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] The Chinese BeiDou  Compass/BeiDou  Second generation of a regional Chinese experimental satellite navigation system  The Chinese GNSS will be a global satellite navigation system consisting of 35 satellites   13 It became operational with coverage in Asia pacific region in December 2011 with 10 satellites in use Frequencies for Compass are allocated in three bands: B1, B2, and B3 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Evolution (1) GPS Evolution: 14 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Evolution (2) 15 GPS GLONASS Galileo Compass Operational 30 MEO 24 MEO 8 MEO 4 MEO, 5 GEO, 5 IGSO Nominal 24 MEO 24 MEO 30 MEO 27 MEO, 5 GEO, 3 IGSO In Full operation 1995- 2011 2018-2020 2018-2020 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Evolution (3)  GLONASS Modernization 16 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Evolution (5)   GNSS evolution has included changes in spreading code modulations that affect spectral shapes and spectrum occupancy CDMA signals in the crowded L1 spectrum: 17 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Evolution (6)  GPS Evolution:  Second civil signal “L2C”  Designed to meet commercial needs •   Higher accuracy through ionospheric correction Began with GPS Block IIR-M in Sep 2005; 24 satellites: ~2014 Third civil signal “L5” Designed to meet demanding requirements for transportation safety-of-life • Uses highly protected Aeronautical Radio Navigation Service (ARNS) band  Begins with GPS Block IIF  1st launch: ~2008 (GPS IIR-M Demo); ~2009 (GPS IIF); 24 satellites: ~2016   Fourth civil signal “L1C”    18 Designed with international partners for GNSS interoperability Begins with GPS Block III First launch: ~2017; 24 satellites: ~2021 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Multi-GNSS Advantages (1/2)   Ideal interoperability provides users a position solution using signals from different GNSS systems:  No additional receiver cost or complexity  No degradation in performance Interoperable = Better Together Than Separate 19 GNSS Technologies GALILEO COMPASS GLONASS GPS Source: M. Shaw, The U.S. Space-Based PNT Current Program and Future Trends, April 2008 18.1.2016 [email protected], [email protected], [email protected] Multi-GNSS Advantages (2/2)  GNSS offers reliable positioning performance in open outdoor environments  Positioning accuracy from even a few millimeters to tens of meters depending on the environment, weather, and technology used     one or two frequency usage code or phase measurements one or multiple receivers GPS Galileo 18 68 9 79 86 26 71 GNSS = GPS, GLONASS, GALILEO, and BeiDou, etc.  GNSS broadens the use of navigations applications even further  Availability and accuracy improves – more satellites and frequencies available 20 GNSS Technologies GNSS: more satellites in e.g. urban canyons 18.1.2016 [email protected], [email protected], [email protected] GNSS Receiver Block Diagram RF front-end Code tracking A/D converter Carrier Tracking Acquisition Bit synchronization Receiver Receiver channel Receiver channel Receiver channel Receiver channel Receiver channel Receiver channel Receiver channel channel Decode nav. data Calculate satellite position Position calculation Calculate pseudorange Basic Block Diagram of GNSS Receiver 21 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Receiver  A GPS/Galileo receiver has three primary tasks:     Acquisition: a three-dimensional search for the satellite's time (code phase), frequency (uncertainty due to Doppler effects and local oscillator errors) and specific PRN code  coarse alignment. Tracking: fine estimation of time, frequency and phases. A Delay Lock Loop (DLL) is typically used to track the code phase. A Phase Locked Loop (PLL) or a Frequency Locked Loop (FLL) is used to track the carrier phase or frequency. Data decoding and position solution. The basic process in acquisition and tracking is correlating the received signal (at baseband) with the assumed code sequence.    22 If there is no prior knowledge, different codes have to be tried to find the first satellite signal. The Doppler effect has to be compensated before correlation. The basic task is to find the correct combination of code phase and Doppler, which match with the received GNSS signal. GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Signal Acquisition & Tracking   Code shift and Doppler frequency acquisition are needed for reliable performance of any CDMA system The code synchronization task is typically split into:        coarse synchronization (or acquisition stage) and fine synchronization (or tracking stage). Acquisition is used to get a rough timing estimate, say within +/- 0.5 chips in case of GPS L1 C/A signal Tracking means finding and maintaining fine synchronization Signal tracking is much easier given the initial acquisition Signal acquisition, however, is usually considered as one of the most challenging tasks in any spread spectrum system Signal acquisition is usually a one-shot estimate. On the contrary, signal tracking is performed in a continuous fashion 23 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] How is the satellite acquired?   In order to determine the user position, delay estimates of the Line-OfSight (LOS) signals from 4 or more satellites are typically needed (alternatively, there is also possible to use carrier phase acquisition, not discussed here). The goal of the acquisition process is: Determine which satellites are on the sky  Determine the Doppler shift  Determine the time delay introduced by the radiowave propagation.  Timing and frequency shift estimation is necessary in order to be able to despread the received signal and obtain the original data   For example, for GPS C/A codes, a full time search of 1023 chips is needed, while the Doppler uncertainty ranges are of the order of ±6 kHz. These ranges can be reduced if some a-priori knowledge of visible satellites and related pseudoranges is available, such as in AssistedGPS concept. 24 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Signal Modulations (1)  The CDMA transmissions from GPS have a rectangular spreading codes (C/A and P) and they are induced by BPSK modulation  The waveform transmitted by the satellite is constructed from a number of components and processes    25 Spreading code generator used to uniquely identify the satellite Data modulation by carrier phase inversion (not in ‘pilot’ signals) For GPS C/A code there is a repetition every 1 ms for the code and ~30 s for the data content, with a ‘super’ frame repeating every 12.5 min GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Signal Modulations (2)   BOC modulation can be described through the introduction of a synchronous subcarrier modulation by a binary square waveform after the code and data modulation stages BOC modulation is defined by two integers (m, n) defining the code chipping rate and the frequency of the binary subcarrier relative to 1.023 MHz   BOC(n,m) refers to a binary signal with a code chipping rate of m x 1.023 MHz and a binary subcarrier with frequency n x 1.023 MHz BOC modulation provides a means to engineer frequency domain separation of signals from different satellite systems or from different services  26 Separation of open access from military e.g. GPS L1C or Galileo L1 open service from GPS M-code or Galileo PRS GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Signal Modulations (3)  Power spectral densities for three sine-phased BOC: spectral shapes to be used for modernized signals  27 BOC(1,1) and BOC(6,1) on open access L1 signals for Galileo and future GPS, and BOC(10,5) for the M-code: GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Signal Modulations (4)  BOC spreading code modulation improves autocorrelation accuracy i.e. estimating the location of the peak of the received signal which is essentially the measurement by which the range to each satellite is estimated     28 Improved multipath performance Better spectral separation with other systems The bandwidth requirement is higher than the traditional BPSK modulation Increased bandwidth however complicates the signal processing and the receiver design GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Signal Modulations (5)  The Composite BOC (CBOC) modulation uses the addition of two signals: the data and pilot signals are formed separately with a common BOC(1,1) part and BOC(6,1) parts with opposite signs   Time multiplex BOC (TMBOC) has been selected for the GPS III L1C spreading code   for Galileo L1 OS The spreading symbol transmitted is either BOC(1,1) or BOC(6,1), and different divisions of the power between the data and the pilot components are possible Alternative BOC modulation has been adopted for Galileo E5 band, AltBOC(15,10)  Similar to BOC but it uses a digital quadrature independent-sideband modulation technique   29 Four independent carriers carrying 4 spreading codes (data and pilot) Early tests from the ‘GIOVE A’ Galileo test satellite shows low susceptibility to multipath potentially providing excellent performance for land applications GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS modulations (6)  AltBOC spectrum AltBOC(15,10) for Galileo E5 30 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Signal Characteristics: GPS L1 GPS L1, 1575.42 MHz Service C/A P(Y) M L1C L1C Component Data Data N/A Data Pilot Spreading Modulation BPSK-R1 BPSK-R10 BOCsin(10,5) TMBOC(6,1,1/11) TMBOC(6,1,1/11) Subcarrier frequency (x 1.023 MHz) - - 10 1 1, 6 Code frequency (x 1.023 MHz) 1 10 5 1 1 Code family Gold m N/A Weil Weil Primary PRN length 1,023 1 week N/A 10,230 10,230 Secondary PRN length - - - - 1800 Data rate 50 bps 50 bps N/A 50 bps 100 bps - Minimum received power dBm -128.5 -131.5 N/A -127 -127 31 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Signal Characteristics: GPS L2 GPS L2, 1227.60 MHz Service CM CL P(Y) M Component Data Pilot Data N/A Spreading Modulation BPSK-R1 511.5 kHz time multiplex BPSK-R1 511.5 kHz time multiplex BPSK-R10 BOCsin(10,5) Subcarrier frequency (x 1.023 MHz) - - - 10 Code frequency (x 1.023 MHz) 0.5 0.5 10 5 Code family m m m N/A Primary PRN length 10230 (20 ms) 767250 (1.5 s) 1 week N/A Secondary PRN length - - - N/A Data rate 50 bps 25 bps 50 bps N/A Minimum received power dBm -131.5 -134.5 to -130 N/A 32 GNSS Technologies -131.5 18.1.2016 [email protected], [email protected], [email protected] Signal Characteristics: GPS L5 GPS L5, 1176.45 MHz 33 Service I Q Component Data Pilot Spreading Modulation QPSK-R10 QPSK-R10 Subcarrier frequency (x 1.023 MHz) - - Code frequency (x 1.023 MHz) 10 10 Code family m m Primary PRN length 10230 (1 ms) 10230 (1 ms) Secondary PRN length 10 20 Data rate 50 bps - Minimum received power dBm -127.9 -127.9 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Signal Characteristics: Galileo E1 Galileo E1, 1575.42 MHz Service OS OS PRS Component Data Pilot Data Spreading Modulation CBOC(6,1,1/11) CBOC(6,1,1/11) - Subcarrier frequency (x 1.023 MHz) Two carriers 1 and 6 Two carriers 1 and 6 - Code frequency (x 1.023 MHz) 1 1 2.5 Code family Random Random N/A Primary PRN length 4092 4092 N/A Secondary PRN length - 25 - Data rate 250 bps - - Minimum received power dBm -127 -127 - 34 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Signal Characteristics: Galileo E6 Galileo E6, 1278.75 MHz 35 Service CS CS PRS Component Data Pilot Data Spreading Modulation BPSK-R5 BPSK-R5 BOCcos(10,5) Subcarrier frequency (x 1.023 MHz) - - 10 Code frequency (x 1.023 MHz) 5 5 5 Code family memory memory N/A Primary PRN length 5115 5115 N/A Secondary PRN length - 100 - Data rate 1000 bps - N/A Minimum received power dBm -125 -125 - GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Signal Characteristics: Galileo E5 Galileo E5, 1191.795 MHz Service E5a E5a E5b E5b Component Data Pilot Data Pilot Spreading Modulation AltBoc(15,10) AltBoc(15,10) AltBoc(15,10) AltBoc(15,10) Subcarrier frequency (x 1.023 MHz) 15 15 15 15 Code frequency (x 1.023 MHz) 10 10 10 10 Code family m m m m Primary PRN length 10230 10230 10230 10230 Secondary PRN length 20 100 4 100 Data rate 50 sps - 250 sps - Minimum received power dBm -125 -125 -125 -125 36 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Signal Comparison  GNSS L1/B1/E1 signal comparison Signal Parameters Global Navigation Satellite Systems BeiDou B1I Galileo GPS L1 E1Ba D1 D2 Transmission chip rate (MHz) 1.023 2.046 2.046 1.023 CDMA code length (chips) 1023 2046 2046 4092 Navigation bit rate (bps) 50 50b 500 250 NH modulation No Yes No No Data bit duration (ms) 20 20 2 4 Code repetition period (ms) 1 1 1 4 a.Galileo Data channel b.1000 bps, after NH code modulation 37 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] GNSS Received Signal Strength  Satellite navigation signals are received at low power levels from the transmitters in the medium Earth orbits    The signal levels on the Earth’s surface are typically -130 dBm Such signals levels are subject to disturbance from many sources of interference Unwanted signals are disturbing the single wanted satellite source from     38 Other navigation satellites in the same constellation with the same (cross-correlation) or different signal structures Other navigation satellites from different constellations Background thermal noise Other external noise sources GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Galileo Services (1) 39 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Galileo Services (2)  Mapping of Galileo navigation signals onto Galileo navigation services 40 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Challenges of Multi-GNSS (1/2)  Perceived benefits of a stand-alone GNSS receiver in view of multi-frequency multi-system constellation - - Benefits in terms of accuracy, availability, reliability, integrity, and so on The main question to be asked here is: What can we achieve with abundant number of satellites in the sky? Implementation complexity vs. expected performance It is essential that the receiver cost will be kept reasonable while achieving the performance benefits from multi-system constellations Some complexity challenges that receiver has to address are: - 41 Radio Frequency (RF) unit requires a complicated implementation with dual/triple built-in front-ends targeted for different frequencies Some tens of channels need to be continuously tracked requiring a huge amount of processing power High bandwidth modernized signals require high sampling rates, that will drain out the receiver power much faster than legacy GNSS signals GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Challenges of Multi-GNSS (2/2)  Is it worth combining all/some systems, or is it just a waste of processing resources without any significant benefits? - Finding proof of Multi-GNSS benefits over complexity - Should have straightforward recommendations on the benefits offered by multi-constellation technologies in defined scenarios - users could have a clear picture of the perceived performance quality from different individual GNSS systems - choosing the best combination that fit their requirements. - Which combination of the constellations would be beneficial in certain region to meet application specific requirement? - GPS + Galileo + BeiDou + GLONASS + IRNSS + QZSS + … - - Effect of inter-system interference in different frequency bands - 42 Operational capabilities the spectrum is already crowded with new modernized multi-GNSS signals GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Channel Quality Index (CQI) Computation  In case of an ideal correlation function for any BPSK-modulated (Binary Phase Shift Keyed) signal, the correlation function resembles a triangle, and the normalized ideal correlation function should have an area equal to 1 square unit. Correlation function for BPSK-modulated signal 43 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] CQI based Multi-GNSS Measurement Selection  The measurement is rejected from position computation if CQI  CQIUpper or CQI  CQI Lower Indications for intelligent measurement selection Power levels of the GNSS signals Information from channel interference monitoring CQI-based rejection Residuals (i.e. actual vs. predicted) of the GNSS measurements (or filter innovations) Contribution to the geometry (dilution of precision) 44 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Simulation Profile Parameters Values Details GPS L1/Galileo E1 max2769B, Bandwidth: 4.2 MHz Configured at 1575.42 MHz BeiDou B1 Max2112, Bandwidth: 10 MHz Configured at 1561.098 MHz Sampling frequency 26 MHz Same for all signals Signal strength Between 45 to 50 dB-Hz Good signal strength No. of satellites 10 GPS, 3 Galileo and 8 BeiDou In total, 21 satellites No. of satellites with multipath 3 GPS, 1 Galileo and 2 BeiDou 6 out of 21 satellites have multipath Multipath power Varying between [-1] to [-3] dB, Step: 1 dB depending on the multipath distance Multipath distance Varying between 50 to 150 meters Step: 50 meters Environmental errors No - 45 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] FGI-GSRx Multi-Frequency Multi-GNSS softwaredefined Receiver  Analysis performed with a Matlab-based software GNSS receiver, the FGI-GSRx  Signal received using radio front-ends  GPS/Galileo/BeiDou/Glonass/IRNSS  Multi-frequency multi-system  Interference monitors  Sensor support GPS dd only Multi-GNSS 46 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] FGI-GSRx Multi-Frequency Multi-GNSS software-defined Receiver (cont.) FGI-GSRx Galileo  GPS BeiDou Glonass IRNSS FGI-GSRx is capable of offering navigation solution with:  GPS L1 signal  BeiDou B1 and B2 signal  Galileo E1 signal  GLONASS L1 signal  IRNSS signal  Dual-frequency (L1/E1/B1 & B2) code-phase based positioning  All research-specific implementation (i.e., Multi-GNSS performance analysis, Jamming detection, Tightly-coupled INS + GNSS, etc.) 47 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Performance Analysis with different GNSS Systems GNSS Constellation 48 Number of Sat. PDOP HPE (95%) [m] 3D RMS [m] Std. Dev. [m] GPS-only (CQI OFF) 10 1.8 13.3 23.0 0.18 GPS-only (CQI ON) 6 3.6 0.9 1.4 0.16 GPS+GAL (CQI OFF) 10+3=13 1.6 10.4 17.8 0.13 GPS+GAL (CQI ON) 6+2=8 3.3 1.0 2.0 0.19 BeiDou-only (CQI OFF) 8 2.1 2.1 20.5 0.07 BeiDou-only (CQI ON) 6 3.4 0.4 1.2 0.05 Multi-GNSS (CQI OFF) 10+3+8=21 1.1 4.5 12.5 0.07 Multi-GNSS (CQI ON) 6+2+6=14 2.0 0.2 0.6 0.05 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Multi-GNSS Performance with Channel Quality Index  Achieved better multi-GNSS performance with intelligent selection of satellites from different constellations Ground plot for 3 systems multi-GNSS solution: 21 GPS+Galileo+BeiDou satellites (10+3+8); CQI OFF 49 GNSS Technologies Ground plot for 3 systems multi-GNSS solution: 14 GPS+Galileo+BeiDou satellites (6+2+6); CQI ON 18.1.2016 [email protected], [email protected], [email protected] Positioning Result with BeiDou   Sky-plot for BeiDou satellites at UTC time 9:30 AM at Finnish Geodetic Institute latitude: N 60.2110°, longitude: E 24.6957° 50 GNSS Technologies  Horizontal error scatter plot  Horizontal CEP(95%): 3.76 m  Horizontal RMS: 1.94 m 18.1.2016 [email protected], [email protected], [email protected] Multi-GNSS Result Analysis BeiDou RMS [m] PDOP GPS Multi-GNSS East North Up 3D East North Up 3D East North Up 3D 0.77 1.78 8.0 8.24 1.19 1.77 1.82 2.8 1.0 1.76 1.88 2.77 2.27 2.15 1.81  Broadcast ionospheric correction models are applied for both BeiDou and GPS satellites  BeiDou PRNs are really low elevated as can be seen from the sky-plot : could be the reason for a higher 3D RMS error  In case of Multi-GNSS solution, only the best two BeiDou satellites with high elevation angles were picked along with the GPS satellites 51 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Position Fix with BeiDou in Google Earth Finnish Geospatial Research Institute, Finland 52 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Summary (1) Modernization performance benefits:      Dual and triple frequency ionospheric corrections New signal acquisition and tracking Positioning performance after modernization Benefits of increased constellation size Details of each system may be found from Interface Control Documents (ICD) publicly available 53 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected] Summary (2)    Adding new signals will improve the accuracy of a GNSS New signals by themselves or used together with the existing signals provide inherently better error performance Currently, GPS transmits only one publicly accessible signal— the coarse acquisition (C/A) code on the L-band carrier known as L1      The new civil (i.e., publicly accessible) signals will include an additional signal on the existing L2 frequency, which will be known as L2C Additionally, a new civil signal will be broadcast at L5 Galileo will include publicly available signals at three different L-band frequencies currently designated as E1 (overlapping GPS L1), E5, and E6 GLONASS will evolve into a CDMA system as well Next generation GNSS signals will provide better opportunities for weak signal acquisition 54 GNSS Technologies 18.1.2016 [email protected], [email protected], [email protected]