Possible Future Changes of the RINEX Format ------------------------------------------- Non-Integer Sampling Rates (Observation File) ************************** Introduction of a more general sampling interval, namely allowing for fractional parts of seconds (e.g. 0.5 second sampling) Problem brought to my attention by: Dr. David S. Coco Applied Research Laboratories The University of Texas at Austin P.O. Box 8029 Austin, Texas 78729 Email: COCO@ARLVS1.ARLUT.UTEXAS.EDU Proposal: +--------------------+------------------------------------------+------------+ *|INTERVAL | Observation interval in seconds | 14X,F14.4 |* | | (Old format for integer values only: I6) | | +--------------------+------------------------------------------+------------+ (Modification of Table A1) Such a record will still conform to RINEX version 1 and 2, since the original field (I6) will be blank and therefore be interpreted as "Interval unknown". Code Fit Interval (Navigation File) *********************************** Bit 17 in word 10 of subframe 2 is a "fit interval" flag which indicates the curve-fit interval used by the CS in determining the ephemeris parameters, as follows (see ICD-GPS-200, 20.3.3.4.3.1): 0 = 4 hours 1 = greater than 4 hours. Together with the IODC values and Table 20-XIA the actual fit interval can be determined. Rick Mach from ARL (E-Mail: RMACH@SGDMAIL1.ARLUT.UTEXAS.EDU) proposes to include the fit flag into the navigation blocks of the RINEX navigation files. Proposal: The second value in the last record of each message contains the fit interval in hours determined using IODC, fit flag, and Table 20-XIA, according to the Interface Document ICD-GPS-200. +--------------------+------------------------------------------+------------+ | BROADCAST ORBIT - 7| - Msg transmit time (sec of GPS week) | 3X,4D19.12 | | | (derived e.g. from Z-count | | | | in Hand Over Word HOW) | | | | - Fit interval (hours) | | | | (see ICD-GPS-200, 20.3.3.4.3.1) | | | | - spare | | | | - spare | | +--------------------+------------------------------------------+------------+ (Modification of Table A4) SV Health (Navigation Message File) *********************************** Proposal: Include also the health of the signal components (bits 18 to 22 of word three in subframe one) and not just the summary bit of the nav data health (bit 17). Time System (Observation File) ****************************** The RINEX Version 2 observation files have been defined in view of a possible inclusion of GLONASS pseudorange and phase observations. GLONASS observables are very similar to the GPS ones: There are also phase observations L1,L2 on the two carriers as well as a C/A code (C1) and two P-code (P1,P2) pseudoranges. RINEX Version 2 needs one supplement, the explicit definition of the time system: Glonass is running on Glonass System Time which is close to UTC(SU). In order to remove possible misunderstandings and ambiguities the header records "TIME OF FIRST OBS" and (if present) "TIME OF LAST OBS" in Glonass and GPS observation files can, in mixed Glonass/GPS observation files must contain a time system denominator defining the system all time tags in the file are referring to (pure GPS files default to GPS and pure GLONASS files default to GLO time system): Example: 1994 3 24 0 0 0.000000 GPS TIME OF FIRST OBS 1994 3 24 23 59 30.000000 GPS TIME OF LAST OBS or 1994 3 23 23 59 51.000000 GLO TIME OF FIRST OBS 1994 3 24 23 59 51.000000 GLO TIME OF LAST OBS Format: +--------------------+------------------------------------------+------------+ |TIME OF FIRST OBS | - Time of first observation record | 5I6,F12.6, | | | (4-digit-year, month,day,hour,min,sec) | | | | - Time system: GPS or GLO | 6X,A3 | | | compulsory in mixed GPS/Glonass files | | | | Defaults: GPS for pure GPS files | | | | GLO for pure Glonass files | | +--------------------+------------------------------------------+------------+ *|TIME OF LAST OBS | - Time of last observation record | 5I6,F12.6, |* | | (4-digit-year, month,day,hour,min,sec) | | | | - Time system: GPS or GLO | 6X,A3 | | | compulsory in mixed GPS/Glonass files | | | | Defaults: GPS for pure GPS files | | | | GLO for pure Glonass files | | +--------------------+------------------------------------------+------------+ (Modification of Table A1) Additional Observation Types in Met Data Files ********************************************** ZD : Dry component of zenith path delay ZT : Total zenith path delay ZT could be used to distribute the zenith path delays estimated for permanently operated GPS sites using their GPS observables. Additional Observation Type in Obs Files **************************************** Several individuals came up with the request to increase the number of significant digits for the signal strength. In the current RINEX definition the signal strength is a number between 1 and 9 to get a coarse receiver-independent indication about the actual signal strength. In order to account for the request we propose to define two new observation types S1 and S2 being the original signal strength values given by the receiver for L1 and L2 tracking. RINEX navigation message files for Glonass ****************************************** As the Glonass navigation message differs in contents from the GPS message too much, we have to define a special Glonass navigation message file. See file GLONASS.TXT! INMARSAT GPS payloads ********************* INMARSAT launched geostationary satellites called AOR-E and IOR having a navigation payload capable of GPS-like signal broadcasting (PRNs are choosen over 100 for thoses GEO satellites), in order to improve GPS performance. (Message from JEAN-MARC.J.M.G.GAUBERT@T4S.thomson.fr) Such satellites could be included into RINEX files using mixed files by using a satellite system "I" and identifying these payloads as "Inn" where nn = PRN-100.