rinex2.txt

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Time, Phase, and Range.

TIME:

  The time of the measurement is the receiver time of the received signals.
  It is identical for the phase and range measurements and is identical for
  all satellites observed at that epoch. It is expressed in GPS time (not
  Universal Time).

PSEUDO-RANGE:

  The pseudo-range (PR) is the distance from the receiver antenna to the
  satellite antenna including receiver and satellite clock offsets (and
  other biases, such as atmospheric delays):

    PR  =  distance +
           c * (receiver clock offset - satellite clock offset +
                other biases)

  so that the pseudo-range reflects the actual behavior of the receiver
  and satellite clocks. The pseudo-range is stored in units of meters.

  See also clarifications for pseudoranges in mixed GPS/GLONASS files in
  chapter 8.1.

PHASE:

  The phase is the carrier-phase measured in whole cycles at both L1 and
  L2. The half-cycles measured by sqaring-type receivers must be converted
  to whole cycles and flagged by the wavelength factor in the header
  section.

  The phase changes in the same sense as the range (negative doppler). The
  phase observations between epochs must be connected by including the
  integer number of cycles. The phase observations will not contain any
  systematic drifts from intentional offsets of the reference oscillators.

The observables are not corrected for external effects like atmospheric
refraction, satellite clock offsets, etc.

If the receiver or the converter software adjusts the measurements using
the real-time-derived receiver clock offsets dT(r), the consistency of the
3 quantities phase / pseudo-range / epoch must be maintained, i.e. the
receiver clock correction should be applied to all 3 observables:

  Time(corr)  = Time(r)  -  dT(r)
  PR(corr)    =  PR(r)   -  dT(r)*c
  phase(corr) = phase(r) -  dT(r)*freq

DOPPLER:

The sign of the doppler shift as additional observable is defined as usual:
Positive for approaching satellites.


4. THE EXCHANGE OF RINEX FILES:

We recommend using the following naming convention for RINEX files:

        ssssdddf.yyt      ssss:    4-character station name designator
                           ddd:    day of the year of first record
                             f:    file sequence number within day
                                   0: file contains all the existing
                                      data of the current day
                            yy:    year
                             t:    file type:
                                   O: Observation file
                                   N: Navigation file
                                   M: Meteorological data file
                                   G: GLONASS Navigation file
                                   H: Geostationary GPS payload nav mess file

When data transmission times or storage volumes are critical we recommend
compressing the files prior to storage or transmission using the UNIX
"compress" und "uncompress" programs. Compatible routines are available on
VAX/VMS and PC/DOS systems, as well.

Proposed naming conventions for the compressed files:

System                      UNIX            VMS             DOS

Obs Files                   ssssdddf.yyO.Z  ssssdddf.yyO_Z  ssssdddf.yyY
Obs Files (Hatanaka compr)  ssssdddf.yyD.Z  ssssdddf.yyD_Z  ssssdddf.yyE
GPS Nav Files               ssssdddf.yyN.Z  ssssdddf.yyN_Z  ssssdddf.yyX
GLONASS Nav File            ssssdddf.yyG.Z  ssssdddf.yyG_Z  ssssdddf.yyV
GEO Nav Files               ssssdddf.yyH.Z  ssssdddf.yyH_Z  ssssdddf.yyU
Met Data Files              ssssdddf.yyM.Z  ssssdddf.yyM_Z  ssssdddf.yyW
Clock Files (see sep.doc.)  ssssdddf.yyC.Z  ssssdddf.yyC_Z

References for the Hatanaka compression scheme: See e.g.

     ftp://igscb.jpl.nasa.gov/igscb/software/rnxcmp/docs/

     IGSMails 1525,1686,1726,1763,1785


5. RINEX VERSION 2 FEATURES
                           

The following section contains features that have been introduced for RINEX
Version 2:


5.1 Satellite Numbers:

Version 2 has been prepared to contain GLONASS or other satellite systems'
observations. Therefore we have to be able to distinguish the satellites
of the different systems:  We precede the 2-digit satellite number with a
system identifier.

        snn                  s:    satellite system identifier
                                   G or blank : GPS
                                   R          : GLONASS
                                   S          : Geostationary signal payload
                                   T          : Transit

                            nn:    - PRN (GPS), almanac number (GLONASS)
                                   - PRN-100 (GEO)
                                   - two-digit Transit satellite number

        Note: G is mandatory in mixed GPS/GLONASS files

                                   (blank default modified in April 1997)

5.2 Order of the Header Records:

As the record descriptors in columns 61-80 are mandatory, the programs
reading a RINEX Version 2 header are able to decode the header records with
formats according to the record descriptor, provided the records have been
first read into an internal buffer.

We therefore propose to allow free ordering of the header records, with the
following exceptions:

- The "RINEX VERSION / TYPE" record must be the first record in a file

- The default "WAVELENGTH FACT L1/2" record must precede all records defining
  wavelength factors for individual satellites

- The "# OF SATELLITES" record (if present) should be immediately followed
  by the corresponding number of "PRN / # OF OBS" records. (These records
  may be handy for documentary purposes. However, since they may only be
  created after having read the whole raw data file we define them to be
  optional.


5.3 Missing Items, Duration of the Validity of Values

Items that are not known at the file creation time can be set to zero or
blank or the respective record may be completely omitted. Consequently
items of missing header records will be set to zero or blank by the program
reading RINEX files. Trailing blanks may be truncated from the record.         |

Each value remains valid until changed by an additional header record.


5.4 Event Flag Records

The "number of satellites" also corresponds to the number of records of the
same epoch followed. Therefore it may be used to skip the appropriate
number of records if certain event flags are not to be evaluated in detail.


5.5 Receiver Clock Offset

A large number of users asked to optionally include a receiver-derived
clock offset into the RINEX format. In order to remove uncertainties if
the data (epoch, pseudorange, phase) have been previously corrected or not
by the reported clock offset, RINEX Version 2.10 requests a clarifying (new)
header record.

It would then be possible to reconstruct the original observations if
necessary.

As the output format for the receiver-derived clock offset is limited to
nanoseconds the offset should be rounded to the nearest nanosecond before it
is used to correct the observables in order to guarantee correct reconstruction.


6. ADDITIONAL HINTS AND TIPS

6.1 Version 1 / Version 2

Programs developed to read RINEX Version 1 files have to verify the version
number. Version 2 files may look different (version number, END OF HEADER
record, receiver and antenna serial number alphanumeric) even if they do
not use any of the new features


6.2 Leading Blanks in CHARACTER fields

We propose that routines to read RINEX Version 2 files automatically delete
leading blanks in any CHARACTER input field. Routines creating RINEX
Version 2 files should also left-justify all variables in the CHARACTER
fields.


6.3 Variable-length Records

DOS, and other, files may have variable record lengths, so we recommend to
first read each observation record into a 80-character blank string and
decode the data afterwards. In variable length records, empty data fields
at the end of a record may be missing, especially in the case of the
optional receiver clock offset.


6.4 Blank Fields

In view of future modifications we recommend to carefully skip any fields
currently defined to be blank (Format fields nX), because they may be assigned
to new contents in future versions.


6.5 2-Digit Years

RINEX version 2 stores the years of data records with two digits only. The
header of observation files contains a TIME OF FIRST OBS record with the full
four-digit year, the GPS nav messages contain the GPS week numbers. From these
two data items the unambiguous year can easily be reconstructed.

A hundred-year ambiguity occurs in the met data and GLONASS and GEO nav
messages: Instead of introducing a new TIME OF FIRST OBS header line it is safe
to stipulate that any two-digit years in RINEX Version 1 and Version 2.xx files
are understood to represent

                80-99:  1980-1999
                00-79:  2000-2079

Full 4-digit year fields could then be defined by a future RINEX version 3.


6.6 Fit Interval