readGLONASSNavigationRINEX: Read a RINEX navigation file for GLONASS satellites

In Rafael-Ayala/asteRisk: Computation of Satellite Position

Read a RINEX navigation file for GLONASS satellites

Description

RINEX (Receiver Independent Exchange Format) is one of the most widely used formats for providing data of satellite navigation systems. The RINEX standard defines several structured text file types, among which navigation files are used to distribute positional information of the satellites. The exact information provided in a RINEX navigation file varies for each satellite navigation system. This function reads RINEX navigation files for satellites of the GLONASS constellation, operated by Russia.

Usage

readGLONASSNavigationRINEX(filename)

Arguments

filename

Path to the GLONASS RINEX navigation file.

Value

A list with two elements. The first element, named header, is a list with the information contained in the header of the RINEX file. For files using RINEX major version 2, it contains the following elements:

rinexVersion	Version of the RINEX format used in the file
rinexFileType	Type of RINEX file
generatorProgram	Program used to generate the RINEX file
generatorEntity	Individual or organization that generated the file
fileCreationDateString	Date-time string indicating when the file was created
refYear	Reference year for system time correction
refMonth	Reference month for system time correction
refDay	Reference day for system time correction
sysTimeCorrection	Correction to system time scale to fine-tune GLONASS time to UTC in seconds. Since GLONASS time is linked to UTC, it should be a very small amount. This is the negative of the parameter typically referred to as tauC.
leapSeconds	Leap seconds introduced since 1980. Useful to convert to GPS time
comments	Miscellaneous comments found in the header of the RINEX file

For files using RINEX major version 3, it contains the following elements:

rinexVersion	Version of the RINEX format used in the file
rinexFileType	Type of RINEX file
satelliteSystem	Character indicating the satellite system. For GLONASS, it should be "R"
generatorProgram	Program used to generate the RINEX file
generatorEntity	Individual or organization that generated the file
fileCreationDateString	Date-time string indicating when the file was created
systemTimeCorrectionType	String indicating the type of system time correction, which defines the exact meaning of the system time correction parameters A0 and A1 and between what time systems these allow conversion. Possible values are (the definition of A0/A1 are given between brackets): GAUT, for GAL to UTC (a0/a1); GPUT, for GPS to UTC (a0/a1); SBUT, for SBAS to UTC (a0/a1); GLUT, for GLO to UTC (TauC/0); GAGP or GPGA, for GPS to GAL (A0G/A1G); GLGP, for GLO to GPS (TauGPS/0); QZGP, for QZS to GPS (a0/a1); QZUT, for QZS to UTC (a0/a1); BDUT, for BDS to UTC (A0UTC/A1UTC); IRUT, for IRN to UTC (A0UTC/A1UTC); IRGP, for IRN to GPS (A0/A1). Note that GLONASS RINEX navigation files will typically contain system time corrections of types either GLUT or GLGP
timeCorrectionA0	A0 parameter (bias) for system time correction in seconds. For corrections of type GLUT, this is equivalent to the field sysTimeCorrection found in headers of GLONASS RINEX navigation files of major version 2, i.e., the negative of tauC. For corrections of type GLGP, this is equivalent to the parameter tauGPS
timeCorrectionA1	A1 parameter (drift) for system time correction in seconds/seconds. Note that this is set to 0 in GLUT and GLGP correction types
timeCorrectionReferenceTime	Reference time for system time corrections, in seconds into GPS/GAL/BDS/QZS/IRN/SBAS week. The correction to be applied to the system time should be calculated as: Correction=A0 + A1*(ephemerisTime - timeCorrectionReferenceTime). Note that GLONASS time is aligned with UTC + 3 hours at a precision of 1 ms, and timeCorrectionReferenceTime is set to 0.
timeCorrectionReferenceWeekNumber	Reference week number for the system time correction reference time. For GPS/GAL/QZS/IRN/SBAS, it is a continuous week scale since 6th of January 1980. For BDS, it is a continuous week scale since 1st of January 2006. For GLONASS, it is set to 0
timeCorrectionSatelliteNumber	String indicating the GNSS satellite that is broadcasting the time system difference for system time correction
UTCType	String indicating the exact UTC type (specific UTC realization) to which system time correction parameters refers to
leapSeconds	Current number of leap seconds
deltaTimeLeapSeconds	Number of leap seconds at a reference date for leap seconds specified by the following week number and week day. Note that the date specified by said week number and day can be either in the past or future
deltaTimeLeapSecondsWeekNumber	Week number for the reference date to which deltaTimeLeapSeconds refers. Given as continuous week number from either 6th of January 1980 (GPS week number) or from 1st of January 2006 (BDS week number). Field leapSecondsTimeSystemIdentifier specifies which of the 2 systems is used.
deltaTimeLeapSecondsDayNumber	Day of week number for the reference date to which deltaTimeLeapSeconds refers. Ranges from 1-7 for reference dates in GPS, or 0-6 for reference dates in BDS. The first day of each week (1 for GPS, 0 for BDS) is considered to be Sunday
leapSecondsTimeSystemIdentifier	String indicating the time system used for the week number and day number for the future/past leap seconds reference date. Can be either "GPS" or "BDS" (BeiDou)
leapSecondsTimeSystemIdentifier	String indicating the time system used for the week number and day number for the future/past leap seconds reference date. Can be either "GPS" or "BDS" (BeiDou)
ionosphericCorrections	List where each element contains the fields required to perform a given type of ionospheric corrections. The contents of each element of this list are detailed below
comments	Miscellaneous comments found in the header of the RINEX file

As mentioned above, for RINEX files of version 3.00 and above, the header element contains a list named ionosphericCorrections. Each element of this list is in turn a list itself, with the following elements:

ionosphericCorrectionType	A string indicating the type of ionospheric correction for which this element provides coefficients. Can be GAL, GPSA, GPSB, QZSA, QZSB, BDSA, BDSB, IRNA or IRNB. The specific coefficients given in the following elements vary depending on the type of ionospheric correction. For GAL, 3 coefficients are given (a0-a2). For GPSA, QZSA, BDSA and IRNA, 4 coefficients are given (alpha0-alpha3). For GPSB, QZSB, BDSB and IRNB, 4 coefficients are given (beta0-beta1)
coefficients	3 (for GAL correction) or 4 (for all other corrections) elements providing the ionospheric correction coefficients. The names of the elements vary depending on the type of correction, as stated above
ionosphericCorrectionTimeMark	Character indicating the transmission time. The field is only mandatory for corrections of type BDSA and BDSB. It can be a letter from "A" to "X", with each letter indicating a 1-hour interval: A=00h-01h, B=01h-02hB, ..., X=23h-24h
ionosphericCorrectionTimeMark	Character indicating the transmission time. The field is only mandatory for corrections of type BDSA and BDSB. It can be a letter from "A" to "X", with each letter indicating a 1-hour interval: A=00h-01h, B=01h-02hB, ..., X=23h-24h
ionosphericCorrectionSV	String indicating the satellite that provided the ionospheric correction parameters. The field is only mandatory for BDSA and BDSB corrections. If multiple sources are available for the same type of BDSA/BDSB correction, these should be given priority according to the satellite that provided them as follows: BDS GEO satellites first, followed by BDS IGSO satellites, and finally BDS MEO satellites

The second element is named messages, and it contains one element for each navigation message found in the RINEX file. Each of these elements is a list with the following elements that provide information about the position of the GLONASS satellite:

satelliteNumber	Slot number of the satellite within the GLONASS constellation. It can be converted to a PRN code by adding 37 to it
epochYear	Epoch year in 4-digit format.
epochMonth	Epoch month
epochDay	Epoch day
epochHour	Epoch hour
epochMinute	Epoch minute
epochSecond	Epoch second
ephemerisUTCTime	A nanotime object indicating the time corresponding to the reported position (ephemeris) in the present message. The time is in UTC, obtained by applying the individual clock bias of the particular satellite (clockBias field of each message) and the latest global GLONASS time bias with respect to UTC (sysTimeCorrection field of the header) to the uncorrected ephemeris time, given by the previous time fields. Corrections are performed as described in the GLONASS system specifications (http://gauss.gge.unb.ca/GLONASS.ICD.pdf)
clockBias	Clock bias (i.e., constant offset) that should be applied to the satellite time in order to obtain an even more accurate UTC time. In seconds
relativeFreqBias	Clock drift of the satellite clock that should be applied in combination with the time difference to the reference time in order to obtain an even more accurate UTC time. In seconds per second
messageFrameTime	Second of the UTC day when the message was transmitted
positionX	X coordinate of the position of the satellite in km, in the ITRF system of coordinates
positionY	Y coordinate of the position of the satellite in km, in the ITRF system of coordinates
positionZ	Z coordinate of the position of the satellite in km, in the ITRF system of coordinates
velocityX	X component of the velocity of the satellite in km/s, in the ITRF system of coordinates
velocityY	Y component of the velocity of the satellite in km/s, in the ITRF system of coordinates
velocityZ	Z component of the velocity of the satellite in km/s, in the ITRF system of coordinates
accelX	X component of the accel of the satellite in km/s, in the ITRF system of coordinates
accelY	Y component of the accel of the satellite in km/s, in the ITRF system of coordinates
accelZ	Z component of the accel of the satellite in km/s, in the ITRF system of coordinates
satelliteHealthCode	Code indicating the health of the satellite. 0 if healthy
freqNumber	Frequency number (k) of the GLONASS satellite. The two frequencies in MHz, f1 and f2, used by the satellite to transmit data can be calculated as follows: f1 = 1602 + k*9/16 and f2 = 1246 + k*7/16
informationAge	Age in days of the observation data used to generate the provided ephemeris

For GLONASS RINEX navigation files of version 3.05 and above, each message element contains the following additional elements:

GLONASSType	String indicating the type of GLONASS satellite. Can be either "GLO" for fist-generation GLONASS satellites, or "GLO-M/K" for second or third generation satellites
updatedDataFlag	Logical indicating if the provided ephemeris data is up to date
numberSatellitesAlmanac	Number of satellites in the almanac for the current transmitted frame. Can be either 4 or 5. Note that almanac data provide coarser information about the location of multiple satellites in a GNSS constellation, and these are not actually included in RINEX navigation files.
ephemerisValidityTimeInterval	Length of the time interval for which the ephemeris is valid, in minutes. Can be 0, 30, 45 or 60.
parityEphemerisValidityTimeInterval	String indicating the evenness or oddity of the time interval for which ephemeris is valid. "Odd" for intervals of 45 minutes, and "Even" for the rest.
tauCSource	String indicating the source providing the value of the tauC parameter, given in the header in field sysTimeCorrection for RINEX navigation messages of version 2, or field timeCorrectionA0 for RINEX navigation messages of version 3 where a time system correction of type GLUT is given. Can be either "On-board" (if it was computed by the on-board satellite processor) or "Ground" (computed and uploaded to the satellite by control segment)
tauGPSSource	String indicating the source providing the value of the tauGPS parameter, given in the header in field timeCorrectionA0 for RINEX navigation messages of version 3 where a time system correction of type GLGP is given. Can be either "On-board" (if it was computed by the on-board satellite processor) or "Ground" (computed and uploaded to the satellite by control segment)
totalGroupDelay	Bias difference between codes broadcasted on L1 and the ionospheric-free combination of the codes broadcasted at L1 and L2, in seconds. This parameter, also known as timing group delay (TGD), should be considered when calculating satellite clock error.
URAI	Value of User Range Accuracy Index (URAI). This is an index giving a measurement of the accuracy of the GNSS ranging accuracy. It is an integer ranging from 0 to 15. 0 indicates the highest accuracy, corresponding to an accuracy of 1 m, while 14 indicates the lowest accuracy, of 512 m. A value of 15 indicates unknown accuracy. For a complete table of equivalence between URAI values and ranging accuracy in meters, see Table 4.4 of GLONASS Interface Control Document (http://gauss.gge.unb.ca/GLONASS.ICD.pdf)
almanacHealthStatus	String indicating the health status of the satellite provided in the almanac (as previously mentioned, full almanac data are not present in RINEX navigation files))

References

https://gage.upc.edu/gFD/ https://www.navcen.uscg.gov/pubs/gps/rinex/rinex.txt ftp://www.ngs.noaa.gov/cors/RINEX211.txt http://acc.igs.org/misc/rinex304.pdf http://gauss.gge.unb.ca/GLONASS.ICD.pdf

Examples

# The file testGLONASSRINEXv2.txt provided with the package includes 5 navigation
# messages from 4 GLONASS satellites

testGLONASSnav <- readGLONASSNavigationRINEX(paste0(path.package("asteRisk"), 
"/testGLONASSRINEXv2.txt"))
testGLONASSnav$header
testGLONASSnav$messages

Rafael-Ayala/asteRisk documentation built on May 16, 2024, 5:24 p.m.