From jimr Tue Mar 23 11:33:34 EST 1999 Received: (from jimr@localhost) by maia.usno.navy.mil (8.8.6 (PHNE_14041)/8.8.6) id LAA19679; Tue, 23 Mar 1999 11:33:24 -0500 (EST) From: Jim Ray (USNO 202-762-1444)Message-Id: <199903231633.LAA19679@maia.usno.navy.mil> Subject: Clock combination progress report To: beutler@aiub.unibe.ch (Prof. Gerhard Beutler (U Bern)), rothacher@aiub.unibe.ch (Markus Rothacher (U Bern)), springer@aiub.unibe.ch (Tim Springer (U Bern)), schaer@aiub.unibe.ch (Stefan Schaer (U Bern)), heike.bock@aiub.unibe.ch (Heike Bock (U Bern)), jdow@esoc.esa.de (John M. Dow (ESOC/ESA)), tmur@esoc.esa.de (Tomas J. Martin Mur (ESOC/ESA)), cagarcia@esoc.esa.de (C. Garcia-Martinez (ESOC/ESA)), reigber@gfz-potsdam.de (Christoph Reigber (GFZ Potsdam)), gend@gfz-potsdam.de (Gerd Gendt (GFZ Potsdam)), dick@gfz-potsdam.de (Galina Dick (GFZ Potsdam)), soeh@gfz-potsdam.de (Wolfgang Soehne (GFZ Potsdam)), jfz@cobra.jpl.nasa.gov (James F. Zumberge (JPL)), mmw@otto.jpl.nasa.gov (Mike Watkins (JPL)), mbh@cobra.jpl.nasa.gov (Michael B. Heflin (JPL)), djeff@cobra.jpl.nasa.gov (David C. Jefferson (JPL)), yeb@cobra.jpl.nasa.gov (Yoaz E. Bar-Sever (JPL)), bock@pgga.ucsd.edu (Yehuda Bock (Scripps)), pfang@pgga.ucsd.edu (Peng Fang (Scripps)), matthijs@pgga.ucsd.edu (Matthijs van Domselaar (Scripps)), kouba@macs.geod.nrcan.gc.ca (Jan Kouba (NRCan)), pierre@geod.nrcan.gc.ca (Pierre Tetreault (NRCan)), mireault@geod.nrcan.gc.ca (Yves Mireault (NRCan)), heroux@geod.nrcan.gc.ca (Pierre Heroux (NRCan)), gerry@mozart.grdl.noaa.gov (Gerry Mader (NOAA)), mark@ness.grdl.noaa.gov (Mark Schenewerk (NOAA)), jimr@maia.usno.navy.mil (Jim Ray (USNO)), jrr@clem.usno.navy.mil (Jim Rohde (USNO)), billk@vulcan.ngs.noaa.gov (William G. Kass (NOAA/NGS)) Date: Tue, 23 Mar 1999 11:33:24 EST X-Mailer: Elm [revision: 212.4] Status: RO To: Analysis Centers Subject: Clock combination progress report Dear Colleagues, Jan reports that he is making good progress with new software to combine satellite and receiver clock values. He will soon send the new software to Tim to be integrated into the IGS Finals combination process. To make further progress, Jan has asked for your help with the following items: 1) Only 2 ACs are currently sending clk files. To validate the new combination software, participation by more ACs is urgently needed (for Final submissions only at present). 2) The clk and sp3 files should have exactly the same values for the satellite clocks (although the units differ: seconds in the clk files and microseconds in sp3). 3) Experience has shown that a few modifications to the clock RINEX format are needed: i) Clock offsets as comment -- As previously agreed, the official IGS values for the satellite antenna offsets (Z components) should be provided in a header comment record: CLK ANT Z-OFFSET(M): II/IIA 1.023; IIR 0.000 COMMENT ii) Clock ref using GPS time -- The GFZ group pointed out that while they normally use ALGO as their fixed reference, they then re-align all clocks to broadcast GPS time. This is done by several other groups too. In this case, it is misleading to indicate only that ALGO is the clk ref. So the format has been modified to allow this option to be documented in the following way: a) suitable comment records should be added to the headers to briefly describe the re-alignment method applied; b) non-zero values for the reference clock (i.e., the negatives of the alignment corrections applied to all other clocks) *must* be included in the clock data records. iii) PRN list -- To aid in reading the clk files, a list of satellites used in the analysis is needed in the file header (e.g.): 27 # OF SOLN SATS G01 G02 G03 G04 G05 G06 G07 G08 G09 G10 G13 G14 G15 G16 G17 PRN LIST G18 G19 G21 G22 G23 G24 G25 G26 G27 G29 G30 G31 PRN LIST iv) List of station clocks -- Please include the reference clock in the count of station clocks "# OF SOLN STA / TRF" and include it in the list "SOLN STA NAME / NUM". v) Multiple reference clocks -- While a linear combination of more than 1 clock can be held fixed as the analysis reference and this is allowed in the clock RINEX format, the ACs are asked *not* to use this option for their IGS submissions. Doing so would complicate the clock combination greatly. However, different clocks can be used as reference for different intervals during the same day (e.g., if the usual reference has a data gap). The header records have been modified to allow for this possibility. A copy of the updated clock RINEX format is provided below. The changes are all backwards compatible. Your assistance in these areas will greatly help with the development of the IGS combined clocks and is very much appreciated. Our special thanks to the ACs already providing clk files. Best regards, --Jim +----------------------------------------------------------------------------+ | TABLE A15 | | CLOCK DATA FILE - HEADER SECTION DESCRIPTION | +--------------------+------------------------------------------+------------+ | HEADER LABEL | DESCRIPTION | FORMAT | | (Columns 61-80) | | | +--------------------+------------------------------------------+------------+ |RINEX VERSION / TYPE| - Format version (2.00) | F9.2,11X, | | | - File type ("C" for Clock Data) | A1,39X | +--------------------+------------------------------------------+------------+ |PGM / RUN BY / DATE | - Name of program creating current file | A20, | | | - Name of agency creating current file | A20, | | | - Date of file creation | A20 | +--------------------+------------------------------------------+------------+ *|COMMENT | Comment line(s) | A60 |* | | | | | | While comments are generally optional, | | | | they must be included for the following | | | | information: | | | | | | | | SATELLITE ANTENNA PHASE CENTER OFFSETS | | | | -------------------------------------- | | | | The vector offset used in data analysis | | | | for the separation of the satellite | | | | antenna phase centers and the satellite | | | | centers of mass must be known. A change | | | | in the Z-direction will appear as a shift| | | | in the satellite clock estimates. By | | | | agreement among the IGS Analysis Centers,| | | | the IGS Z-offsets are given below and a | | | | COMMENT record of this type should always| | | | be included: | | | | | | | | CLK ANT Z-OFFSET(M): II/IIA 1.023; IIR 0.000 | | | | | | | * REQUIRED for data types "Ax" | | | | | | | | | | | | TIMESCALE RE-ALIGNMENT | | | | ---------------------- | | | | If estimated clock values have been | | | | uniformly shifted in timescale, e.g., to | | | | GPS time, the method applied should be | | | | noted here. In addition, non-zero clock | | | | values should be reported in the clock | | | | data records for the analysis reference | | | | clock, corresponding to the negative of | | | | alignment correction applied to all the | | | | receiver and satellite clocks. The | | | | analysis reference clock should still be | | | | listed as "ANALYSIS CLK REF" even though | | | | it will have non-zero values. | | | | | | | | * REQUIRED for data types "Ax", if | | | | applicable | | | | | | +--------------------+------------------------------------------+------------+ *|LEAP SECONDS | Number of leap seconds since 6-Jan-1980 | I6 |* | | Recommended as an aid to convert from | | | | GPS time to UTC | | +--------------------+------------------------------------------+------------+ |# / TYPES OF DATA | - Number of different clock data types | I6, | | | stored in the file | | | | - List of clock data types | 5(4X,A2) | | | | | | | The following clock data types are | | | | defined in RINEX Version 2: | | | | | | | | "AR": Data analysis results for receiver | | | | clocks derived from a set of | | | | network receivers and satellites | | | | wrt to a reference clock fixed in | | | | the analysis | | | | "AS": Data analysis results for satellite| | | | clocks derived from a set of | | | | network receivers and satellites | | | | wrt to a reference clock fixed in | | | | the analysis | | | | "CR": Calibration measurements for a | | | | single GPS receiver wrt an | | | | external local reference clock | | | | "DR": Discontinuity measurements for a | | | | single GPS receiver | | | | "MS": Monitor measurements for the | | | | broadcast satellite clocks wrt a | | | | standard timescale | | | | | | +--------------------+------------------------------------------+------------+ |STATION NAME / NUM | - 4-character receiver name designator | A4,1X, | | | - Unique receiver identifier, | A20,35X | | | preferably the DOMES number for | | | | fixed stations | | | | | | | | * REQUIRED for data types "CR" & "DR" | | | | | | +--------------------+------------------------------------------+------------+ |STATION CLK REF | Unique identifier for external | A60 | | | reference clock being used as the | | | | standard for calibration | | | | | | | | * REQUIRED for data type "CR" | | | | | | +--------------------+------------------------------------------+------------+ |ANALYSIS CENTER | Name of Analysis Center | | | | - 3-character IGS AC designator | A3,2X, | | | - Full name of Analysis Center | A55 | | | | | | | * REQUIRED for data types "Ax" & "MS" | | | | | | +--------------------+------------------------------------------+------------+ |# OF CLK REF | - Number of analysis clock references | I6,1X, | | | (satellite or receiver clocks) listed | | | | under "ANALYSIS CLK REF" | | | | - Start epoch (in GPS time): | | | | year (4 digits),month,day,hour,min, | I4,4I3, | | | second | F10.6, | | | [default: blank start and stop times | | | | imply single "ANALYSIS CLK REF" | | | | applies for entire file] | | | | - Stop epoch (in GPS time): | 1X, | | | year (4 digits),month,day,hour,min, | I4,4I3, | | | second | F10.6 | | | [default: blank start and stop times | | | | imply single "ANALYSIS CLK REF" | | | | applies for entire file] | | | | | | | | NOTE: Multiple groups of "# OF CLK REF" | | | | "ANALYSIS CLK REF" records can be used | | | | for changes in analysis clock reference | | | | within a single analysis file. | | | | | | | | * REQUIRED for data types "Ax" | | | | | | +--------------------+------------------------------------------+------------+ |ANALYSIS CLK REF | List of the analysis clock references | | | | (repeat for each reference clock | | | | enumerated in the previous record) | | | | - Name of the receiver or satellite | A4,1X, | | | used as the fixed reference in data | | | | analysis | | | | - Unique identifier for reference | A20,15X, | | | clock (if a receiver), preferably | | | | the DOMES number for fixed stations | | | | - Optionally a non-zero value for the | E19.12,1X | | | the apriori clock constraint can be | | | | provided (unit: seconds). | | | | | | | | NOTE: If all analysis clock estimtes are | | | | re-aligned (e.g., to broadcast GPS time) | | | | then the fixed analysis clock will have | | | | non-zero values corresponding to the | | | | negative of the alignment corrections | | | | applied to all other clocks. The non- | | | | zero clock values for the reference must | | | | be reported in the clock data records | | | | together with the other clock values, | | | | but the reference clock should still be | | | | listed here. The method of re-alignment | | | | should be described in header comment | | | | records. | | | | | | | | * REQUIRED for data types "Ax" | | | | | | +--------------------+------------------------------------------+------------+ |# OF SOLN STA / TRF | - Number of receivers included in the | I6,4X, | | | clock data records (including the | | | | analysis reference clock even if it | | | | has zero values and is not given in | | | | the data records) and listed in the | | | | following header records | | | | - Terrestrial reference frame or | A50 | | | SINEX solution for the station/ | | | | receiver coordinates which match | | | | the clock solution | | | | | | | | * REQUIRED for data types "Ax" | | | | | | +--------------------+------------------------------------------+------------+ |SOLN STA NAME / NUM | For each station/receiver included in | | | | the clock data records, as well as the | | | | analysis reference clock even if it has | | | | zero values and is not included in the | | | | data records (number given in the | | | | previous header record), include one | | | | record with the following information: | | | | - 4-character station/receiver name | A4,1X, | | | designator | | | | - Unique station/receiver identifier, | A20,35X | | | preferably the DOMES number for | | | | fixed stations | | | | | | | | * REQUIRED for data types "Ax" | | | | | | +--------------------+------------------------------------------+------------+ |# OF SOLN SATS | - Number of different satellites in the | I6,54X | | | clock data records and listed in | | | | following header records | | | | | | | | * REQUIRED for data types "Ax" | | | | | | +--------------------+------------------------------------------+------------+ |PRN LIST | List of all satellites reported in this | 15(A1,I2, | | | file. Each satellite name is a | 1X) | | | 3-character string: | | | | - "Gnn" where nn is the PRN number | | | | for GPS satellite | | | | - "Rnn" where nn is the almanac number | | | | for GLONASS satellite | | | | | | | | * REQUIRED for data types "Ax" | | | | | | +--------------------+------------------------------------------+------------+ |END OF HEADER | Last record in the header section. | 60X | +--------------------+------------------------------------------+------------+ Records marked with * are optional +----------------------------------------------------------------------------+ | TABLE A16 | | CLOCK DATA FILE - DATA RECORD DESCRIPTION | +-------------+-------------------------------------------------+------------+ | OBS. RECORD | DESCRIPTION | FORMAT | +-------------+-------------------------------------------------+------------+ |TYP/EPOCH/CLK| - Clock data type (AR, AS, CR, DR, MS) | A2,1X, | | | | | | | - Receiver or satellite name | A4,1X, | | | - Receiver name is the IGS 4-character | | | | designator | | | | - Satellite name is a 3-character string: | | | | - "Gnn" where nn is the PRN number | | | | for GPS satellite | | | | - "Rnn" where nn is the almanac number | | | | for GLONASS satellite | | | | | | | | - Epoch in GPS time (not local time!): | | | | year (4 digits),month,day,hour,min, | I4,4I3, | | | second | F10.6, | | | - Number of data values to follow | I3,3X, | | | - Clock data in the following sequence: | | | | - Clock bias (seconds) | E19.12,X | | | - Clock bias sigma [optional] (seconds) | E19.12 | +-------------+-------------------------------------------------+------------+ |TYP/EPOCH/CLK| - Clock rate [optional] (dimensionless) | E19.12,X, | | (CONT) | - Clock rate sigma [optional] (dimensionless)| E19.12,X, | | | - Clock acceleration [optional] (per second) | E19.12,X, | | | - Clock acceleration sigma [optional] | E19.12 | | | (per second) | | | | | | | | The continuation line is necessary for more | | | | than 2 data values | | | | | | | | NB: For data types "Ax", "CR", and "MS", | | | | clock data are in the sense of | | | | reported station/satellite clock | | | | *minus* reference clock value. | | | | For data type "DR", clock data are | | | | the sense of clock value after | | | | discontinuity *minus* before. | | | | | | | | Clock data apart from bias values are | | | | optional. However, if any optional values | | | | are included, then all lower order values | | | | must be supplied even if optional (although | | | | zero values may be given) | | | | | | +-------------+-------------------------------------------------+------------+ +------------------------------------------------------------------------------+ | TABLE A17 | | CLOCK DATA FILE - EXAMPLE FOR ANALYSIS DATA | +------------------------------------------------------------------------------+ ----|---1|0---|---2|0---|---3|0---|---4|0---|---5|0---|---6|0---|---7|0---|---8| 2.00 CLOCK DATA RINEX VERSION / TYPE TORINEXC V9.9 USNO 3-APR-96 00:10 PGM / RUN BY / DATE CLK ANT Z-OFFSET(M): II/IIA 1.023; IIR 0.000 COMMENT EXAMPLE OF A CLOCK DATA FILE COMMENT IN THIS CASE ANALYSIS RESULTS ARE INCLUDED COMMENT No re-alignment of the clocks has been applied. COMMENT 10 LEAP SECONDS 2 AS AR # / TYPES OF DATA USN USNO USING GIPSY/OASIS-II ANALYSIS CENTER 1 1994 07 14 0 0 0.000000 1994 07 14 20 59 0.000000# OF CLK REF USNO 40451S003 -.123456789012E+00 ANALYSIS CLK REF 1 1994 07 14 21 0 0.000000 1994 07 14 21 59 0.000000# OF CLK REF TIDB 50103M108 -0.123456789012E+00 ANALYSIS CLK REF 4 ITRF96 # OF SOLN STA / TRF GOLD 40405S031 SOLN STA NAME / NUM AREQ 42202M005 SOLN STA NAME / NUM TIDB 50103M108 SOLN STA NAME / NUM HARK 30302M007 SOLN STA NAME / NUM USNO 40451S003 SOLN STA NAME / NUM 27 # OF SOLN SATS G01 G02 G03 G04 G05 G06 G07 G08 G09 G10 G13 G14 G15 G16 G17 PRN LIST G18 G19 G21 G22 G23 G24 G25 G26 G27 G29 G30 G31 PRN LIST END OF HEADER AR AREQ 1994 07 14 20 59 0.000000 6 -0.123456789012E+00 -0.123456789012E+01 -0.123456789012E+02 -0.123456789012E+03 -0.123456789012E+04 -0.123456789012E+05 AS G16 1994 07 14 20 59 0.000000 2 -.123456789012E+00 -.123456789012E-01 AR GOLD 1994 07 14 20 59 0.000000 4 -.123456789012E-01 -.123456789012E-02 -.123456789012E-03 -.123456789012E-04 AR HARK 1994 07 14 20 59 0.000000 2 .123456789012E+00 .123456789012E+00 AR TIDB 1994 07 14 20 59 0.000000 6 .123456789012E+00 .123456789012E+00 .123456789012E+00 .123456789012E+00 .123456789012E+00 .123456789012E+00 ----|---1|0---|---2|0---|---3|0---|---4|0---|---5|0---|---6|0---|---7|0---|---8| +------------------------------------------------------------------------------+ | TABLE A18 | | CLOCK DATA FILE - EXAMPLE FOR CALIBRATION/DISCONTINUITY DATA | +------------------------------------------------------------------------------+ ----|---1|0---|---2|0---|---3|0---|---4|0---|---5|0---|---6|0---|---7|0---|---8| 2.00 CLOCK DATA RINEX VERSION / TYPE TORINEXC V9.9 USNO 3-APR-96 00:10 PGM / RUN BY / DATE EXAMPLE OF A CLOCK DATA FILE COMMENT IN THIS CASE CALIBRATION/DISCONTINUITY DATA GIVEN COMMENT 10 LEAP SECONDS 2 CR DR # / TYPES OF DATA USNO 40451S003 STATION NAME / NUM UTC(USNO) MASTER CLOCK VIA CONTINUOUS CABLE MONITOR STATION CLK REF END OF HEADER CR USNO 1994 07 14 20 59 50.000000 2 .123456789012E+00 .123456789012E-01 CR USNO 1994 07 14 22 19 30.000000 2 -.123456789012E+00 .123456789012E-02 DR USNO 1994 07 14 22 23 14.500000 2 -.123456789012E+01 .123456789012E+00 CR USNO 1994 07 14 23 44 50.000000 2 -.123456789012E+02 .123456789012E+00 ----|---1|0---|---2|0---|---3|0---|---4|0---|---5|0---|---6|0---|---7|0---|---8|