Multi-approach gravity field models from Swarm GPS data

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SINEX format

• Format description (EGSIEM)
• Complete description (IERS)
• SINEX-related utilites at Mathworks

Requirements for the contents

• Only gravity field parameters (no initial state vectors, drag coefficients, etc);
• No degree 1 coefficients;
• Normal equations must be normalized by the a priori sigma squared (which each institute must estimate themselves).

Example (IfG)

• Plain text (GROOPS format)
  • Normal Matrix (2.4Mb)
  • RHS vector (12Kb)
• SINEX (2.5Mb) Important: the extension “.txt” has been appended to this file so that it shows on browser
• tarball with all files (2Mb)
• Code:
  • fileSinex.h
  • fileSinex.cpp
  • normalsSphericalHarmonics2Sinex.cpp

Example (AIUB)

• Code:
  • write_SNX.f90
• Example header:
  • only the COMMENT block is mandatory for the EGSIEM-SINEX files, since the information of GM (earth_gravity_constant), R (radius), maximum degree (max_degree) and tide system (tide_system) is needed to correctly read and process the files.

+FILE/REFERENCE
*INFO_TYPE_________ INFO________________________________________________________
 DESCRIPTION        GRACE monthly gravity field
 CONTACT            ulrich.meyer@aiub.unibe.ch
 SOFTWARE           Bernese GNSS Software Version EGSIEM
 INPUT              monthly NEQs: MErr
-FILE/REFERENCE

+FILE/COMMENT
 modelname              EGSIEM_AIUB_RL01
 earth_gravity_constant 3.9860044150e+14
 radius                 6.3781363000e+06
 max_degree             90
 norm                   fully_normalized
 tide_system            tide_free
-FILE/COMMENT

+INPUT/ACKNOWLEDGMENTS
*AGY DESCRIPTION________________________________________________________________
 EGS EGSIEM-contribution from Astronomical Institute of the University of Berne
-INPUT/ACKNOWLEDGMENTS

Example (ASU)

• .mat files (MATLAB)
  • Normal Matrix (1.4Mb)
  • RHS vector (8Kb)
• SINEX (2.5Mb) Important: the extension “.txt” has been appended to this file so that it shows on browser
• zip archive with all files (2.4Mb)
• Code:
  • sinex_asu_01c.m. ** Important:** requires additional routines found in the “private” directory in the zip archive and the extension “.txt” has been appended to this file so that it shows on browser
• Readme:

Sample code to export the normal equation matrix related to gravity field solutions
in the SINEX for the DISC consortium according to guidelines provided by https://jgte.github.io/gswarm/SINEX/.

After running sinex_asu_01c.m, one should obtain the file 'GSWARM_NE_SABC_ASU_2014-08_01_IFG.snx'.

The code is free to use, in its entirety or in parts.

Ales Bezdek, bezdek@asu.cas.cz, 15. 3. 2018