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GNSS & GPS III

GNSS & GPS III. - Documented initially in 2010 - Revised on April 26, 2013 (added GNSS and GPStk). L5 Safety of Life (SOL) available with first GPS IIF launch ( 28 May 2010 ) Two PRN ranging codes are transmitted on L5: the in-phase code (denoted as the I5-code);

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GNSS & GPS III

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  1. GNSS & GPS III - Documented initially in 2010 - Revised on April 26, 2013 (added GNSS and GPStk)

  2. L5 Safety of Life (SOL) available with first GPS IIF launch (28 May 2010) Two PRN ranging codes are transmitted on L5: the in-phase code (denoted as the I5-code); and the quadra-phase code (denoted as the Q5-code). Both codes are 10,230 bits long and transmitted at 10.23 Mbit/s (1mS repetition). ★ Improves signal structure for enhanced performance ★ Higher transmitted power than L1/L2 signal (~3db, or twice as powerful) ★ Wider bandwidth provides a 10x processing gain ★ Longer spreading codes (10x longer than C/A) ★ Uses the Aeronautical Radionavigation Services band L5 Navigation message The L5 CNAV data includes SV ephemerids, system time, SV clock behavior data, status messages and time information, etc.

  3. L2C • - the civilian receivers can now directly measure the ionospheric error • - transmitted by the so-called Block IIR-M (1st on 26 September 2005, SVN53, PRN17) and later design satellites (new hardware required) • - providing improving accuracy of navigation, providing an easy to track signal, and acting as a redundant signal in case of localized interference.. • -two distinct PRN code sequences : • the 'Civilian Moderate' length code (called CM): 10,230 bits long, repeating every 20 mS, 511,500 bit/s, Modulated with the CNAV Navigation Message • and the 'Civilian Long' length code (called CL): 767,250 bits, 1500 mS, No modulated data--> ~250 times stronger correlaton than L1 C/A-code. • L2C has 2.7 dB greater data recovery and 0.7 dB greater carrier-tracking, although its transmission power is 2.3 dB weaker than the L1 C/A signal. • CNAV Navigation message • upgraded version of the original NAV navigation message: higher precision representation and more accurate data • the new pseudo-packetized CNAV format, (VS. a frame / subframe architecture) for the same type of information (Time, Status, Ephemeris, and Almanac) • ★ uses Forward Error Correction (FEC) in a rate 1/2 convolution code, so while the navigation message is 25 bit/s, a 50 bit/s signal is transmitted. • ★ The GPS week number is now represented as 13-bits, or 8192 weeks, and only repeats every 157.0 years. Meaning the next return to zero won't occur until the year 2137. This is larger compared to the L1 NAV message's use of a 10-bit week number, which returns to zero every 19.6 years. • ★ There is a packet that contains a GPS to GNSS time offset. This allows for interoperability with other global time-transfer systems, such as Galileo and GLONASS, both of which are supported. • ★ The extra bandwidth enables the inclusion of a packet for differential correction, to be used in a similar manner to satellite based augmentation systems and can be used to correct the L1 NAV clock data. • ★ Every packet contains an alert flag, to be set if the satellite data can not be trusted. This means users will know within 6 seconds if a satellite is no longer usable. Such rapid notification is important for safety-of-life applications, such as aviation. • ★ Finally, the system is designed to support 63 satellites, compared with 32 in the L1 NAV message.

  4. L1C -The L1C will be available with first Block III launch, currently scheduled for 2014. -L1C was developed to serve as the baseline signal format for Japan's Quasi-Zenith Satellite System (QZSS). -The PRN codes are 10,230 bits long and transmitted at 1.023 Mbit/s. It uses both Pilot and Data carriers like L2C. -As of 2007, the modulation technique is not finalized. ★ Implementation will provide C/A code to ensure backward compatibility ★ Assured of 1.5 dB increase in minimum C/A code power to mitigate any noise floor increase ★ Data-less signal component pilot carrier improves tracking ★ Enables greater civil interoperability with Galileo L1 CNAV-2 : L1C Navigation message -it is 1800 bits (including FEC) and is transmitted at 100 bit/s: 9-bit time information, 600-bit ephemeris, and 274-bit packetized data payload .

  5. General Info • Announcements from the Vice President and the White House in 1998 • In 2000, the U.S. Congress reaffirmed the effort; referred to it as 'GPS III'. • (new GS, satellites, additional nav signal for C & M) • A goal of 2013 has been established • Lockheed Martin was awarded the GPS III Space Segment contract on May 15, 2008, the first launch is projected for 2014. • Raytheon was awarded the Next Generation GPS Control Segment (OCX) contract on Feb 25, 2010. • L5 signals will be transmitted as standard by the next generation of GPS satellites (IIF) (last generation of Block II, signed in 1996, Boeing): • -On 24 March, 2009, a GPS satellite carrying a special test payload for transmitting a new navigation signal in the L5 frequency band was launched. • - The first GPS IIF satellite was launched by a Delta IV-M+(4,2) rocket on 28 May 2010.: SVN62, PRN25, slot=B2 • The second GPS IIF satellite: on 16 July 2011, : SVN63, PRN01, slot=D2 • -The 3rd GPS IIF :on 4 October 2012, SVN65, PRN24, slot=A1

  6. Block IIF : Launch Plan as of April 2013 (Ref: Wikipedia) Block IIIA

  7. Comparison of GNSS systems (Ref: wikipedia)

  8. Ref: wikipedia

  9. * GPS signals in the code for Rinex 2.11 and Rinex 3.xx: if( type == "C1" ) type = "C1C"; else if( type == "P1" ) type = "C1P"; else if( type == "L1" ) type = "L1P"; else if( type == "D1" ) type = "D1P"; else if( type == "S1" ) type = "S1P"; else if( type == "C2" ) type = "C2C"; else if( type == "P2" ) type = "C2P"; else if( type == "L2" ) type = "L2P"; else if( type == "D2" ) type = "D2P"; else if( type == "S2" ) type = "S2P"; * RINEX HEADER SAMPLES: RINEX 2.11 VS. RINEX 3.xx : Rinex 2.11: 9 C1 P1 P2 L1 L2 D1 D2 S1 S2# / TYPES OF OBSERV Rinex 3.xx: G 16 L1C L2X L2W L5X C1C C2X C5X C2W D1C D2X D2W D5X S1C SYS / # / OBS TYPES S2X S2W S5X SYS / # / OBS TYPES R 8 L1C L2P C1C C2P D1C D2P S1C S2P SYS / # / OBS TYPES G 19 C1C L1C D1C S1C C1W L1W S1W C2X L2X D2X S2X C2W L2W SYS / # / OBS TYPES D2W S2W C5X L5X D5X S5X SYS / # / OBS TYPES R 15 C1C L1C D1C S1C C1P L1P S1P C2C L2C D2C S2C C2P L2P SYS / # / OBS TYPES D2P S2P SYS / # / OBS TYPES E 8 C1X L1X D1X S1X C5X L5X D5X S5X SYS / # / OBS TYPES

  10. ( Ref: Rinex 3.xx forrmat documentation by Werner Gurtner & Lou Estey )

  11. ( Ref: Rinex 3.xx forrmat documentation by Werner Gurtner & Lou Estey )

  12. ( Ref: http://www.rtklib.com )

  13. ( Ref : http://www.rtklib.com )

  14. ( Ref: http://www.rtklib.com )

  15. GPStk:

  16. GPStk directory structure: Ref: http://www.gpstk.org

  17. Dagoberto Salazar’s contribution:

  18. The following Rinex 3 classes have been added:

  19. Civil Navigation Message processing for GPS III signals is implemented in the following classes

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