Precise Orbit and Clock Products

Orbit and clock products that become available as part of the MGEX data analysis are made available at the CDDIS MGEX product archive as well as mirror sites hosted by IGN and ENSG. The products are stored in weekly directories (identified by the 4-digit GPS week) and identified by a three letter analysis center ID identifying the contributing agency. Six MGEX analysis centers are presently contributing dedicated multi-GNSS products for MGEX on a routine basis:

  • Centre National d'Etudes Spatiales (CNES), Collecte Localisation Satellites (CLS), Groupe de Recherche de Géodésie Spatiale (GRGS)
  • Center for Orbit Determination in Europe (CODE)
  • GeoForschungsZentrum Potsdam (GFZ)
  • Shanghai Observatory (SHAO)
  • Technische Universität München (TUM)
  • Wuhan University

In addition, a copy of the QZSS final orbit and clock products generated by the Japan Aerospace Exploration Agency (JAXA) is made available to MGEX users on a courtesy basis.

First orbit and clock products for selected new constellations were provided by the MGEX Analysis Centers (ACs) in mid 2012 (GPS week 1680). Since then an increasing number of multi-constellation products covering up to five global or regional navigation satellite systems has become available. In addition to precise ephemerides, clock products with sampling intervals down to 30 s, Earth orientation parameters (EOPs), and biases are generated by individual ACs. Selected ACs also provide station coordinates and EOPs in the Solution INdependent EXchange (SINEX) format. An overview of products available as of March 2019 is provided in the following table.

CNES/CLS GRG0MGXFIN GPS+GLO+GAL Satellite orbits and clocks (15 min; *.SP3)
Satellite and station clocks (30 s; *.CLK)
Site coordinates and EOPs (*.SNX)
Loyer et al. (2018)
CODE COD0MGXFIN GPS+GLO+GAL+BDS+QZS Satellite orbits and clocks (5 min; *.SP3)
Satellite and station clocks (30 s/5 min; *.CLK)
Earth orientation parameters (12 h; *.ERP)
Biases (1 d; *.BIA)
Dach et al. (2018),
Prange et al. (2018)
GFZ GFZ0MGXRAP GPS+GLO+GAL+BDS+QZS Satellite orbits and clocks (15 min; *.SP3)
Satellite and station clocks (30 s/5 min; *.CLK)
Earth orientation parameters (1 d; *.ERP)
Biases (1 d; *.BIA)
GFZ MGEX website
JAXA JAX0MGXFIN GPS+GLO+QZS Satellite orbits and clocks (5 min; *.SP3)
Satellite and station clocks (30 s; *.CLK)
Site coordinates and ERPs (*.SNX)
SHAO SHA0MGXRAP GPS+GLO+GAL+BDS Satellite orbits and clocks (15 min; *.SP3)
Satellite and station clocks (5 min; *.CLK)
TUM tum GAL+BDS+QZS Satellite orbits and clocks (5 min; *.SP3) Selmke et al. (2018)
Wuhan Univ. WUM0MGXFIN GPS+GLO+GAL+BDS+QZS Satellite orbits and clocks (15 min; *.SP3)
Satellite and station clocks (5 min; *.CLK)
Earth orientation parameters (1 d; *.ERP)

Discontinued and former products with legacy file naming are listed below:

CNES/CLS grm until week 2024 Loyer et al. (2016)
CODE com until week 1961 Prange et al. (2015), Prange et al. (2016)
GFZ gfm until week 1789 Uhlemann and Fritsche (2014)
GFZ gbm until week 2037 Deng et al. (2014), Uhlemann et al. (2015)
JAXA qzf until week 1938
Wuhan Univ. wum until week 2033 Guo et al. (2016)

Different satellite antenna PCOs and PCVs are used by the MGEX analysis centers processing BeiDou:

Analysis center BDS PCOs/PCVs
CODE MGEX conventional as included in igs14.atx
GFZ ESA estimates, Dilssner et al. (2014)
SHAO unknown
Wuhan Univ. WU estimates, Guo et al. (2016)

Orbit and clock analyses as well as SLR residuals based on the aforementioned MGEX products are posted on the MGEX Analysis web page. The analyses are updated on a weekly basis.

File naming

File names for most MGEX products as well as the DCB proucts of CAS and DLR are based on a new naming scheme proposed for IGS products, which is inherited from the RINEX3 file naming convenion and comprises five fields separated by underscores ("_"). The initial 10-char field specifies the analysis center (3-char), a version number (1-digit), the campaign/project (3-char) and a product type (3-char). The remaining fields provide the start epoch (11-digit year, day-of-year, hour, minute), the nominal product period (2-digit number and unit designator such as D (days), L (months), or Y (years), the sampling interval (2-digit number and unit designator), and, finally, the product type (3 chars.).

  • Currently, only the version identifier 0 is used within MGEX
  • The project specification for MGEX is MGX.
  • Product types:
    • FIN: final analysis
    • RAP: rapid analysis
  • Content types:
    • CLK: receiver and/or satellite clock parameters
    • ERP: Earth rotation parameters
    • ORB: satellite orbits
    • OSB: observable-specific signal bias
    • SOL: variance/covariance information or normal equations
  • File formats:
  • Compression methods:
    • gz: gzip
    • Z: UNIX compress

Broadcast Ephemerides

In addition to the aforementioned precise orbit and clock products, combined multi-GNSS broadcast ephemeris files are made available by BKG, IGS, and TUM/DLR.

Institution File name Constellations Notes
BKG BRDC00WRD_S_yyyydddhhmm_01D_MN.rnx.gz GPS+GLO+GAL+BDS Converted from stream RTCM3EPH on
IGS BRDC00IGS_R_yyyydddhhmm_01D_MN.rnx.gz GPS+GLO+GAL+BDS
Merged from receiver-generated RINEX navigation files
TUM/DLR brdmdddn.yyp GPS+GLO+GAL+BDS
Merged from streams of about 35 stations

The various broadcast ephemerides are provided in the form of RINEX3 navigation files:

  • The brdm product is available in the annual MGEX BRDM archives of the Crustal Dynamics Data Information System (CDDIS) and the daily MGEX RINEX archives of the Institut Géographique National (IGN).
  • The IGS BRDC product is available in the annunal data archives of CDDIS and the daily data archives at IGN.
  • BKG's product can independently be obtained from the BKG BRDC archive, which also provides near-real-time version updated at 15 min intervals in a sliding window mode.
As a special product, MGEX offers daily sets of GPS CNAV data recorded from a global subset of MGEX stations. Details of the contents and format are provided in the CNAV section of the MGEX GPS status page.

Differential Code Biases

Proper knowledge of differential code biases (DCBs) is essential in many navigation applications but also non-navigation aplciations such as ionospheric analysis and time transfer. With the plethora of new signals offered by modernized and new GNSSs, the need for a comprehensive multi-GNSS DCB product arises.

As part of the IGS Multi-GNSS Experiment (MGEX) two different DCB products are presently provided by the Institute of Geodesy and Geophysics (IGG) of the Chinese Academy of Sciences (CAS) in Wuhan and the German Aerospace Center (DLR) at the CDDIS and IGN product archives:

Institution Products Constellations and Signals Notes
CAS CAS0MGXRAP_yyyyddd0000_01D_01D_DCB.BSX.gz GPS(C1C,C1W,C2L/S/X,C2W,C5Q/X)
Wang et al. 2015
DLR DLR0MGXFIN_yyyy0010000_nnu_07D_DCB.BSX.gz
GAL(C6C) since Q2/2017
BDS(C5X) since Q1/2019
QZS(C1C/X,C2L/S/X C5Q/X) since Q3/2017
Montenbruck et al. 2014

The CAS DCBs are provided in a preliminary version of the Bias SINEX (BSX) format whereas DLR used the Version 1.00 of February 2016 until I/2017 and the Version 1.00 of December 2016 starting with II/2017. The December 2016 version of the Bias SINEX format uses a 4-digit year number whereas the version of February 2016 uses a 2-digit year number for specifying the validity intervals.

The DCBs are derived from ionosphere-corrected pseudorange differences and cover all available signals of GPS, GLONASS, Galileo, and BeiDou. No DCBs are presently provided for QZSS, since the availability of only one spacecraft and the lack of a calibrated reference station do not allow a separation of satellite and station-specific DCBs.

Both DCB products offer continuous data since Jan. 1, 2013 but differ in the coverage and update rate. The satellite and station biases computed by the CAS are generated on a daily basis with a latency of 2-3 days and made available in daily BSX files. The DLR product is updated on a 3-monthly basis and comprises weekly averages of the satellite biases. In addition a full set of daily satellite AND station biases is provided for reference purposes and trend analyses. Note that station DCBs are not required in common positioning applications where they will typically be absorbed in clock offsets or inter-system biases.

Real-Time Products

Complementary to the multi-GNSS observation data provided in the real-time streams of individual MGEX stations, a distinct broadcast ephemeris stream (RTCM3EPH) is made available at the IGS-IP products caster. The stream is combined from a broadcast ephemerides delivered by a globally distributed set of stations and covers the complete GPS, GLONASS and Galileo constellation. For further information and alternative broadcast ephemeris streams users are referred to the BKG web page on Broadcast Ephemeris from EUREF & IGS Real-time GNSS Resources.

Last Updated: 2019/03/13 15:24:49
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