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Reliable Time from GNSS Signals

Reliable Time from GNSS Signals

GNSS & THE LAW

Reliable from GNSS Signals

ANDREAS BAUCH PHYSIKALISCH-TECHNISCHE BUNDESANSTALT, , PETER WHIBBERLEY NATIONAL PHYSICAL LABORATORY, TEDDINGTON, UK

Precise time is crucial to a great variety of economic activities around the world. viding the required time information. Communication systems, electric power grids, and financial networks all rely on All GNSS scales are based precision timing for synchronization and operational efficiency. Here, the authors on the international reference time scale, Coordinated (UTC). will show how the time obtained from GNSS satellite signals is related to the There are two types of offsets between international time scale, UTC, and explain how GNSS receivers can be used to these system time scales and UTC. Inte- ensure that they are operating correctly, as reliable and traceable sources of time. ger offsets exist because leap sec- onds have been introduced in UTC, but recise timing is essential for users to determine the time to within 100 not in GPS time, Galileo System Time the functioning of any global billionths of a second (100 ), (GST), or BeiDou time. In addition, at satellite system without the cost of owning and operat- the level, “small” offsets (GNSS). GNSS themselves are ing atomic .” The “time” is exist. But when it comes to court, ques- Ppart of national critical infrastructures used with at least two connotations: tions may be asked such as “Who told in key sectors of the economy such as time interval and time of . In many the satellite what time-of-day it electricity distribution, telecommunica- countries, laws or decrees prescribe the is?” Or “Are the time-of-day and the tions, and all modes of transport, which use of certain units such as the second time unit provided by GNSS traceable require accurate and reliable time to of the International System of units (or to UTC?” Traceability is a key concept operate effectively. In all of these sec- SI) for time interval and its inverse, the in , and requires an unbro- tors, the time information required can hertz, for . ken chain of comparisons or calibrations be obtained from GNSS signals, under- In official use, a link to the national between a result and a pinned by the international infrastruc- time standards maintained in National reference standard, with measurement ture for time and frequency metrology. Metrology Institutes (NMIs) – such as uncertainty assigned to each step. The In this article, we will describe this the National Physical Laboratory (NPL) words in italics are close to the defini- global metrology system for timekeep- in the United Kingdom and Physika- tion of the term in the International ing, explain how it underpins the time lisch-Technische Bundesanstalt (PTB) Vocabulary of Metrology (known by its information provided by GNSS, and in Germany – is essential if measure- French abbreviation, VIM), and apply introduce the important concept of ments are being made with any claim to just as much to a measurement of time traceability in measurement. accuracy. Many countries have a “time based on received GNSS satellite signals According to the U.S. Government’s law” that prescribes adherence to a cer- as to any other measurement procedure. official GPS website: “In addition to , institute, is entrusted explicitly with its metrology system and the realization of , and altitude, the Global Posi- dissemination. In practice, the common UTC to which the national realizations tioning System (GPS) provides a critical global time scale, Coordinated Univer- and thus legal adhere. A section fourth – time. Each GPS satel- sal Time (UTC), provides the underly- on dissemination of GNSS times follows, lite contains multiple atomic clocks that ing reference in all countries, with the including some detail about the “time”- contribute very precise time data to the appropriate and summer time related quantities included. Finally, GPS signals. GPS receivers decode these offsets applied. we discuss options for the validation signals, effectively synchronizing each From a purely technical point of of GNSS time signals so that their use receiver to the atomic clocks. This enables view, GNSS signals are capable of pro- can be compliant with legal prescrip-

38 InsideGNSS MARCH/APRIL 2017 www.insidegnss.com tions and briefly touch upon the issue seen by the International Committee for formed by delegates from the 58 Mem- of liability. Weights and Measures (CIPM), made up ber States who meet every four . of 18 elected representatives from the The BIPM has the particular task to The BIPM and Time Scales NMIs. The CIPM also has a number of generate and disseminate the interna- The International Bureau of Weights Consultative Committees that provide tional reference time scale UTC, which and Measures (BIPM) is the intergov- more detailed guidance and coordi- is carried out by its Time Department. ernmental organization which organizes nation of specific areas of metrology, UTC is a post-processed time scale; it is and supports the joint work of Member including the Consultative Committee the result of worldwide cooperation of State signatories of the Conven- for Time and Frequency (CCTF). Over- 78 institutes (as of March 2017), mainly tion on matters related to metrology all supervision and strategy formulation NMIs, but also including some astro- and measurement standards. The BIPM, is provided by the General Conference nomical observatories and research which is located in Paris, France, is over- on Weights and Measures (CGPM), centers that operate high-quality atomic Tabulating Time-Related Data from Galileo and GPS Navigation Messages Here, we describe the time-related data from the navigation mes- GPS time. GNSS receivers that generate data files according to the sages of Galileo and GPS, which are almost identical in format Receiver Independent Exchange Format RINEX version 3.01 and and content. higher report these quantities. As an example, see the header of a Clock Offset from System Time navigation file (Figure 3 in the main text) retrieved from a GNSS timing receiver, operated at PTB. The file was generated on day The correction between the individual space vehicle clock and 310 of 2016, day 6 of GPS 1921 (WN), which starts with GNSS system time at a given time is calculated from the transmit- second 518400 (TOW). Quantities of interest here are shown in ted parameters, here shown for Galileo in Table 1 (European GNSS the red lines. GPGA represents GGTO as just defined, although [Galileo] Open Service Signal In Space Interface Control Docu- the wording on the sign can be a bit ambiguous. ment, OD SIS ICD, European Union (2010), listed in Additional Resources [IB1]). The corresponding definition for GPS is given in Parameter Designation Bits Units §20.3.3.3.1.8 and the associated Table 20-1 in Global Positioning t0C Clock correction data 14 Multiples of 60 s Systems Directorate Systems Engineering & Integration, Interface reference, Time of Week

Specification IS-GPS-200H, listed in Additional Resources [IB2]. –34 af0 SV clock bias correction 31 Multiples of 2 s Week Numbering and Time of Week coefficient GPS week number zero (0) started at midnight UTC(USNO) Jan. –46 af1 SV correction 21 Multiples of 2 s/s 5, 1980 /morning of Jan. 6, 1980, according to 6.2.4 adapted from coefficient

specifications described in [IB2]. The Galileo week zero corre- –59 2 af2 SV clock drift rate 6 Multiples of 2 s/s sponds to GPS week 1024, which after week roll-over was reported correction coefficient as week zero. The GST start was 00:00 UTC Sunday, Aug. Table 1. Galileo SV clock correction parameters, adapted from [IB1]. 22, 1999. At that epoch, GST was ahead of UTC by 13 . As 12 bits are reserved for the week number, roll over occurs only Parameter Designation Bits Unit after about 78 years. Table 2 lists the parameters, as reported in Table 63 of [IB1]. WN Week Number 12 TOW Time of Week 20 seconds Offset Between System Time and UTC Both GPS and Galileo provide parameters to estimate time in Table 2. GST parameters, adapted from [IB1]. UTC from the system time for a given epoch. The parameters comprise the integer seconds offset due to the leap seconds in Parameter Designation Bits Unit –30 UTC, and offset and rate coefficients for the accurate prediction A0 Constant term of polynomial 32 2 s of the difference (at ns-level). They are listed in Table 3, based on –50 A1 First order term of polynomial 24 2 s §20.3.3.5.2.4 of [IB2] and Table 69 of [IB1]. As previously stated, ΔtLS count before leap 8 s offset from UTC means from UTC(USNO) in the case of GPS and second adjustment from a prediction of UTC, based on UTCE, in the case of Galileo. t UTC data reference time of week 8 3600 s We can see from Figure 1 that – at least for the period covered – ot

the differences are marginal, but not zero and not identical. Tables WNot UTC data reference week number 8 Week 2 and 3 represent the means of accurately determining “time-of- WNLSF Week number of leap second 8 Week day” in UTC via GNSS signals. adjustment Offset Between System Times DN Day number at the end of which a 3 Day In support of interoperability, GPS and Galileo report the pre- leap second is dicted time offset between the two system times, termed GGTO, introduced in the navigation message. This is covered by §5.1.8 of [IB1] and ΔtLSF Leap second count after leap 8 S §30.3.3.8 in [IB2], respectively. In the sign convention of [IB2] the second adjustment quantity GGTO is equal to Galileo System Time (GST) minus Table 3. Parameters of the GST to UTC conversion, adapted from [IB1].

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signatories of the Mutual Recognition Arrangement (MRA) 5 established by the CIPM. The MRA provides a framework for NMIs to demonstrate the equivalence of their measurement standards and services. Thus, traceability to UTC can in theory 0 be obtained equivalently from any of the NMIs that are signa- tories of the CIPM MRA. However, there is a stumbling block: USNO is not an NMI and thus did not sign the MRA, so it is

Time di erence / ns Time di erence –5 not able to demonstrate formal traceability to UTC through its UTC(USNO) time scale based on its internal measurement capabilities. The other institutes involved are NMIs and are –10 covered by the MRA. Further measures are therefore needed 57299 57389 57479 57569 57659 to obtain traceability to UTC in the strict sense by receiving MJD GPS signals. FIGURE 1 Reference time scales for GPS (yellow), GLONASS (red) and Gali- Metrology worldwide is coordinated through the regional leo (green) in comparison with UTC during one year, ending at Modified metrology organizations (RMOs), with memberships based (MJD) 57659, September, 28 2016. on the NMIs of the countries represented. There are currently six RMOs, as shown in Figure 2. The European Association of National Metrology Institutes, known as EURAMET, is the RMO that covers Europe. It coordinates the cooperative activi- ties of NMIs in Europe in fields such as metrology research, traceability of to the SI units, international rec- ognition of national measurement standards, and certification of the Calibration and Measurement Capabilities (CMCs) of its members. The work of EURAMET is organized in 12 Technical Committees (TC), of which one deals with Time and Frequency (TC-TF). The EURAMET website lists the institutes participat- ing in TC-TF, which are the institutes responsible for time and frequency in each country, and the current contact persons FIGURE 2 Regional Metrology Organizations Worldwide, © BIPM . A study of the legal time regulations and practices across clocks and time transfer equipment, which we will collectively Europe was published by the EURAMET TC-TF in 2011, refer to as timing centers. Clock and time transfer data are and is available for download from the EURAMET website regularly reported to the BIPM, which calculates UTC early in

40 InsideGNSS MARCH/APRIL 2017 www.insidegnss.com orbit parameters, and parameters that sage to provide output data in the form Another class of instruments outputs relate the individual satellite clock time of local reference clock minus GNSS the time-of-day information, converted to the underlying GNSS system time. time. Recommendations on a common from the navigation message, either in Details of the data format are given in data file format and a standard formula a clock display, in standard electrical the sidebar “Tabulating Time-Related and parameters for data evaluation time codes such as IRIG, or by acting as Data from Galileo and GPS Navigation were developed jointly by the BIPM a (NTP) server Messages.” As explained in the context and the CCTF. For wider use, in par- for time dissemination in networks. We of Figure 1, the system times are steered ticular for positioning and navigation, will consider the use of these devices in towards realizations of UTC, except for the “Receiver Independent Exchange” the next section. the integer second offsets that result format, RINEX, was developed as part The EURAMET TC-TF has pre­ from different choices of origin and of the work of the International GNSS pared a technical guide for calibration system time scales (other than that of Service (IGS). laboratories that use GPSDOs as their GLONASS) not applying leap second For this article, the more relevant source of frequency or time traceability adjustments. receivers are those designed to dis- to UTC, which was published in 2016, cipline the frequency of their inbuilt and is available for download (see Addi- Using GNSS Signals as a Source of UTC quartz oscillator (or rubidium atomic tional Resources). The guide discusses in Two distinct types of GNSS timing frequency standard) to GNSS time and detail the requirements that a calibration receiver have been developed. The more to deliver standard frequency (typically laboratory should meet in order to claim sophisticated “scientific” receivers, 10 megahertz) and a one-pulse-per-sec- formal traceability to UTC when using a sometimes called time transfer receiv- ond (1 PPS) output signals representing GPSDO. The considerable variations in ers, determine the pseudorange of each the GNSS time. A GPS-only device like regulations across Europe created some satellite in view with respect to signals this is often called a GPS-disciplined complications, but there was agree- from a local reference clock connected oscillator (GPSDO), and is widely used ment on a range of core requirements. to the receiver, and use the informa- in calibration laboratories, industry, and In particular, calibration of the GPSDO tion contained in the navigation mes- wherever accurate frequency is required. is recommended if low uncertainties

PolaRx5 Reference Receivers

Adaptive narrow and wide band interference mitigation, multiple logging sessions and more all on low power of <2 W

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(SS-US in mechanism for the timing properties Fig u re 4) of GNSS signals. The GNSS monitor- has become ing bulletins published free of charge by a hot topic: several NMIs, including NPL and PTB, how to pro- provide a readily available means of con- tect against firming that the broadcast GNSS timing spoofing, signals were correct. The bulletins sup- a n d h o w port the demonstration of traceability to verify or between measurements made using the FIGURE 3 B1 RINEX 3.01 navigation file header from day 310 of year 2016 from a GNSS receiver operated at PTB authenti- space signals, for example when using a cate the sig- GPSDO, and the UTC(k) time scale of nals arriving at the the issuing NMI. receiver? The subject To be more specific, we can consider was recently treated the situation in PTB. Up to eight GNSS in depth in Inside receivers from four different manufac- GNSS in an article turers have been operated during recent by Gianluca Cap- years, and their observations are com- arra et alia (2016) pared daily. Standard daily observation listed in Additional files in the formats described in the Resources. paper by Pascale Defraigne and Gérard FIGURE 4 Flow of information and signals between a GNSS Ground Seg- In some GNSS Petit, (2015) and listed in Additional ment (GS) and Space Segment (SS), through the Signals in Space (SIS) to the Receiver (REC) and the final output of the application (APPL). markets, including Resources, and – as far as possible — civil aviation and the in RINEX format are publicly available are claimed (better than 1 maritime sector, certification has become for the previous day at in various folders. and a method is needed to verify correct certification covers the receiver perfor- These files provide a direct reference to operation when the GPSDO is in use, for mance, assuming well-defined proper- UTC(PTB) for the experienced user. For example by monitoring its internal con- ties of the received signal at the SS-US the public, a weekly Time Service Bulle- trol parameters or by comparing it with border (such as carrier-to-noise density tin (TSB) is published at ftp://ftp.ptb.de/ a second, independent, standard. ratio, level of multipath, and interfering pub/time/bulletin/. Users in Germany signals in neighboring frequency bands). who seek to obtain traceability to Ger- Validation of GNSS-Based Timing This topic was addressed inInside GNSS man legal time from GNSS signals are Figure 4 sketches the steps from GNSS in an article by Jules McNeff (2012) listed advised to take note of the contents of signal generation in the GNSS Ground in Additional Resources. One kind of the TSB, or are guided to perform data Segment (GS), through the Space Seg- certification employs a certified signal analysis by following standard proce- ment (SS), to the user application. Inside simulator as a source of signals to be fed dures to obtain evidence of the perfor- the perimeter of GNSS operations, there directly to the receiver. This, of course, mance of their local equipment. Near- are certainly numerous cross-checks to covers only part of the problem. A full real-time services that also verify the full verify the properties of the GNSS system certification test would have to take into data content of the navigation message time and the parameters of the naviga- account the antenna, including its envi- (see again the sidebar on page 39) are not tion message. Each of the GNSS opera- ronmental conditions and the antenna yet available, but such services are possi- tors has established a public web portal cable. ble to set up using the real-time services with information about anomalies, sig- In the timing community, such for- provided by the IGS. nal outages etc. In the case of Galileo, the mal procedures are rare. The 78 labo- European GNSS Service Centre provides “Notice GNSS timing receivers from at least five Networks Advisories to Galileo Users” (NAGUs). different, commercially independent Time distribution in Local Area Net- But these do not represent a satellite-by- manufacturers. There is therefore some works using the Network Time Proto- satellite publicly available verification of variety of both hardware (front-end, col (NTP) or the Precision Time Proto- signal content, or a means to establish signal processing etc.) and the propri- col (PTP) has become well established, traceability of measurements based on etary software to provide data outputs, and a wide variety of equipment is on GNSS signals to national or interna- enabling confidence in their perfor- the market to serve the needs. For secu- tional standards. mance to be built up through cross- rity reasons, the servers used are often The situation at the boundary line comparisons. This network of receiv- not connected to the internet. Instead between the space and user segments ers can be considered as a verification of obtaining time via NTP from public

42 InsideGNSS MARCH/APRIL 2017 www.insidegnss.com servers, the time-of-day information tor of the GNSS has done its job well. for identifying the root cause of the included in the GNSS SIS is translated Many readers will remember the , affected users would also have into the NTP or PTP messages. The line “GPS Ground System Anomaly” report- to provide proof of underlying fault. As labelled REC-APPL in Figure 4 indicates ed by the U.S. Air Force on Jan 27, 2016. users will lack the necessary insights into that the transmission of time informa- In its official press release it stated: “On the complex chain underlying GNSS tion from a receiver into an application 26 January at 12:49 a.m. MST, the 2nd time applications, provision of such is another process whose correctness Space Operations Squadron at the 50th proof may be very difficult. The detailed needs to be assessed carefully to verify Space Wing, Schriever Air Force Base, legal background was reported in an traceability. One option, implemented Colo., verified users were experiencing earlier contribution in this “GNSS & the in some equipment, is to cross-check GPS timing issues. Further investigation Law” column (see Additional Resourc- the time-of-day information from the revealed an issue in the Global Position- es). According to this analysis, no con- GNSS signals against the time signals ing System ground software which only tractual liability could be evoked if the received through a second reference, affected the time on legacy L-band sig- root cause lies in the performance of one which would typically be a dedicated nals. This change occurred when the old- of the GNSS systems. Non-contractual standard frequency and time broadcast est vehicle, SVN 23, was removed from liability is limited due to the doctrine service, such as DCF77 in Germany and the constellation. While the core navi- of sovereign immunity and applicable MSF in the U.K. gation systems were working normally, national laws on state liability. Both the Within Europe, new regulations the coordinated universal time timing U.S. and Russian governments tradition- drafted by the financial services regula- signal was off by 13 which ally deny any legal responsibility for the tor, the European Securities and Mar- exceeded the design specifications.” The performance of GPS or GLONASS sys- kets Authority (ESMA), specify that publicly available information, derived tem and signal performance, and beginning January 3, 2018, all automated from the detailed analysis of the event also has not made any commitments in trades are timestamped to UTC with an provided from the proceedings of ION this respect. uncertainty no greater than 100 micro- GNSS+ 2016 and listed in Additional Regarding Galileo, the European seconds. After consultation, ESMA has Resources, indicates that the param- Union (EU) as the owner of the system concluded that GPS and other GNSS eters A0 and WNOT (see Table 3) were and the European GNSS Agency (GSA) services can be used as the time source transmitted incorrectly by an increasing as the user services provider, theoretical- provided that measures are put in place number of satellites for several . ly bear non-contractual liability under to demonstrate traceability and that the However, the ICD states that such data Article 340 of the Treaty on the Func- receiver is working correctly. Exchanges should be regarded as invalid if WNOT is tioning of the European Union (TFEU). and trading venues must therefore mod- so different from the current epoch (here However, compensation is to be made ify or upgrade their timing infrastruc- more than two years). “in accordance with the general princi- ture to provide evidence of UTC trace- If any user application was affected ples common to the laws of the Member ability at all times when trading is taking by this anomaly – it affected only tim- States”, which leaves a significant level of place, even if they are already distribut- ing users, not positioning services – the uncertainty. Furthermore, the European ing time through their networks from a software routines evaluating the SIS Commission has recently published so- GNSS source. messages were not sufficiently following called Service Definition Documents for With such regulations in place in the underlying ICD. It therefore appears the Open Service and Search and Rescue finance, and similar timing require- unlikely that the GNSS operator could initial services. Both documents contain ments appearing in other areas such be held liable for any losses incurred in terms and conditions for the use of these as smart-grids and the efficient use of this or similar cases, although it will not services, including a rather far-reaching renewable energy, the question of the be possible to make any definitive state- disclaimer of liability. The EU and the liability of GNSS operators in the event ments until a claim has been tested in a other entities involved do not offer any of users incurring significant costs as a court of law. warranty regarding service availability, result of errors in the signals received continuity, accuracy, integrity, reliability at the SS-US interface (see Figure 3) has A Look Ahead at Liability and fitness for purpose. They shall not become quite topical. Although we are To conclude this section, we try to ana- be held liable for any damages resulting not qualified to answer legal questions, lyze the aspect of liability from our from the use of the service, other than our understanding is that the so-called (non-expert) point of view. Should a in accordance with Article 340 TFEU. Interface Control Documents (ICDs), event cause real loss or damage Even for Galileo, affected users will be cited in the sidebar for the cases of GPS to users of GNSS time applications, the faced with significant legal and factual and Galileo, are the primary references legal treatment of claims would be faced barriers to receiving compensation. in any controversy. If the signals gener- with enormous complexities. While On the international level, there are ated in the Space Segment comply with the stakeholders involved would likely no specific legal instruments governing the specifications in the ICDs, the opera- undertake all necessary investigations liability for GNSS signals and services. www.insidegnss.com MARCH/APRIL 2017 InsideGNSS 43 GNSS & THE LAW

For more than 15 years, the matter has Additional Resources Authors been discussed within the International [1] Baumann, I., “Liability for GNSS Signals and Ser- Andreas Bauch has a diploma Maritime Organisation (IMO), the vices”, Inside GNSS, Vol. 10, No. 6, Nov./Dec. 2015, in . He joined Phyika- pp. 38-45, 2015. lisch-Technische Bunde- International Civil Aviation Organiza- [2] Caparra, G., and C. Wullems, S. Ceccato, S. Stu- sanstalt, Braunschweig, Ger- tion (ICAO) and the International Insti- raro, N. Laurenti, O. Pozzobon, R.T. Ioannides, and many (PTB) as a PhD student, tute for the Unification of Private Law M. Crisci, “Design Drivers and New Trends for Navi- being initially engaged in (UNIDROIT). However, all these efforts gation Message Authentication Schemes for GNSS studies on frequency shifting have not resulted in any common posi- Systems”, InsideGNSS, Volume Sept./Oct. 2016, pp. effects in caesium atomic clocks. He got his PhD 64 – 73, 2016. (Dr. rer. nat.) from Johannes-Gutenberg Univer- tion or the development of any proposal sity, Mainz, Germany. Since then he has been [3] Defraigne, P. and G. Petit, “CGGTTS-Version 2E: for a legal instrument. Overall, users will always involved in time and frequency metrolo- an extended standard for GNSS Time Transfer,” gy, focused at first on the development and therefore have enormous difficulties in Metrologia, Volume 52, G1, 2015. operation of atomic clocks, later more and more receiving compensation for their loss or [4] Dow, J. M., and R.M. Neilan, and G. Gendt, “The damage arising from malfunctioning of on time comparison techniques (GNSS, TWSTFT). International GPS Service: celebrating the 10th He became responsible for PTB’s Time Unit Labo- GNSS time services. anniversary and looking to the next ,” Adv. ratory in 1991. Today he is Head of PTB’s Time Space Res. 36 (2005) 320. Dissemination Working Group and as such has Conclusion [5] EURAMET TC-TF, “Guidelines on the Use of GPS the management responsibility for the operation Precise time is crucial to a great variety Disciplined Oscillators for Frequency or Time Trace- of PTB’s time dissemination services. He has ability, Technical Guide No. 3, Version 1.0 (2016),” of economic activities around the world. served as delegate to the Consultative Commit- free download at http://www.euramet.org/publi- tee for Time and Frequency (CCTF) and to Study Communication systems, electric power cations-media-centre/cgs-and-tgs/. Group 7 of the International Telecommunication grids, and financial networks all rely on [6] European GNSS (Galileo) Open Service Signal Union. Between 2009 and 2013 he chaired the accurate and reliable timing for synchro- In Space Interface Control Document, OD SIS ICD, EURAMET Technical Committee for Time and Fre- nization and operational efficiency. The Issue 1, February 2010, European Union 2010; quency. Since 2009 he is member of ESA’s GNSS free availability of GPS time has enabled Listed as [IB1] in the main text. Advisory Committee which he chaired between 2012 and 2015. He has authored and cost savings for companies that depend [7] Global Positioning Systems Directorate Systems Engineering & Integration, Interface Specification co-authored more than 100 papers in refereed on precise time and has led to significant IS-GPS-200H, 24. Sept. 2013; Listed as [IB2] in the journals and conference proceedings. advances in capability. main text. Peter Whibberley is a Senior Research Scientist in the Time Companies worldwide use GPS to [8] Guinot, B. and E.F. Arias, “Atomic time-keeping and Frequency group at the time-stamp business transactions, pro- from 1955 to the ”, Metrologia, Volume 42, National Physical Laboratory pp. 20-30, 2005. viding a consistent and accurate way to (NPL), the UK’s national mea- maintain records and ensure their trace- [9] Gurtner, W., and Estey, L., “RINEX The Receiver surement institute. After gradu- ability. Major financial institutions use Independent Exchange Format Version 3.01,” ating from Oxford University, Werner Gurtner, Astronomical Institute University UK, Peter worked on far infrared and millimeter GPS to obtain precise time for setting of Bern, and Lou Estey, UNAVCO Boulder, Co., 22 the internal clocks used to timestamp wavelength measurement at NPL until moving to June 2009. Time and Frequency in 1990. For 10 years he was financial transactions. Large and small [10] ITU Study Group 7, “ITU Handbook: Satellite part of a small team that constructed a prototype businesses are turning to automated sys- Time and Frequency Transfer and Dissemination, caesium fountain primary frequency standard at tems that can track, update, and manage International Telecommunication Union,” Geneva, NPL. Since then Peter has acted as lead scientist for multiple transactions made by a global 2010. the Time activities at NPL, including operation of network of customers, and these require [11] Joint Committee for Guides in Metrology, the national time scale UTC(NPL), the satellite- “International vocabulary of metrology — Basic based time transfer links to other national timing the accurate timing information avail- and general concepts and associated terms centres, and the time dissemination services. Peter able through GPS and from other GNSS (VIM)”, Working Group 2 of the Joint Committee participates in a number of international commit- in the near future. for Guides in Metrology (JCGM/WG 2) (2008). tees, including Study Group 7 of the International We have shown in this article how [12] Kovach, K., and P.J. Mendicki, E.D. Powers, and Telecommunication Union, and has been elected the time obtained from GNSS satellite B. Renfro, “GPS Receiver Impact from the UTC Offset to take over as Chair of the Technical Committee for Time and Frequency within EURAMET, the Euro- signals is related to the international (UTCO) Anomaly of 25-26 January 2016”, Proceed- ings of the 29th International Technical Meeting of pean Association of NMIs, in May 2017. time scale, UTC, and explained how the ION Satellite Division, ION GNSS+ 2016, Portland, Ingo Baumann is co-founder GNSS receivers can be used, with some Oregon, September 12-16, 2016 and partner of BHO Legal in Cologne, Germany, a boutique care to ensure that they are operat- [13] Lapuh, R., “EURAMET Countries’ Legal Time law firm for European high tech- ing correctly, as reliable and traceable Regulations and Practices,” EURAMET e.V., 2011, nology projects mainly in the for download at http://www.euramet.org/Media/ sources of time. space sector. Ingo studied law at docs/Publications/other_publications/Booklet_ the Universities of Muenster and P1117_V20110510RL.pdf. Manufacturers Cologne. His doctoral thesis, written at the Institute The GNSS timing receiver described in [14] McNeff, J., “GPS Receiver Specifications - Com- for Air and Space Law in Cologne, examined the inter- this article and operated at PTB was a pliance and Certification”,Inside GNSS, Vol. 7, No. 3, national and European law of satellite communica- May/June 2012, pp. 50-56, 2012. MESIT model GTR51 from MESIT tions. Baumann worked several years for the German [15] Piriz, R., et alia, “The Time Validation Facility defence, s.r.o., Uherské Hradiště, Czech Aerospace Centre (DLR), including as head of the DLR (TVF): An All-New Key Element of the Galileo Oper- Galileo Project Office and CEO of the DLR operating Republic. ational Phase”, in Proc. IFCS2015_paper_5130, 2015. company for the German Galileo Control Center.

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