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         WELCOME TO THE IfG FTP PRODUCT SERVER
           ftp.tugraz.at/outgoing/ITSG/tvgogo/
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            IfG - gravity field solutions (SST-HL only)

                    18. July 2017

             Graz University of Technology
               Institute of Geodesy (IfG)
                      (former ITSG)

                   Norbert Zehentner
                   zehentner@tugraz.at
                   +43 316 873 6344
or:
                   Torsten Mayer-Guerr
                   mayer-guerr@tugraz.at
                   +43 316 873 6359

Adress:            Steyrergasse 30/III
                   8010 Graz, Austria

Introduction:
-------------

We provide different gravity field solutions produced at the Institute of Geodesy. Access is granted without any
registration and free of charge. All provided solutions can be used for scientific research or any other
application. Nevertheless, if you publish any results based on our products please add an acknowledgement
and one of the following references:
Zehentner, N. and Mayer-Gürr, T. (2015). “Precise orbit determination based on raw GPS measurements.”
In: Journal of Geodesy. issn: 0949-7714. doi: 10.1007/s00190-015-0872-7

or

Zehentner, N. (2017). "Kinematic orbit positioning applying the raw observation approach to observe time variable gravity"
PhD Thesis, Graz University of Technology, DOI:10.13140/RG.2.2.33916.33927

Currently solutions are stored in the following directory:
  /gravityFieldModels                    a static gravity field model based on GRACE and GOCE orbits
  /gravityFieldModels/"satellite name"   monthly gravity field solutions based on orbits from a single satellite
  /gravityFieldModels/Grace              combined monthly gravity field solutions based on orbits of Grace 1 and Grace 2
  /gravityFieldModels/Swarm              combined monthly gravity field solutions based on orbits of all three Swarm satellites
  /gravityFieldModels/Combined           combined monthly gravity field solutions based on orbits from all available satellites

The static gravity field is based on orbit positions from GRACE A and B (01.02.2003 - 28.02.2013) and GOCE(01.11.2009 -
31.01.2013).

For Version 3 of combined solutions the included satellites are listed in a file (usedSatellites.txt) contained in the folder.
No such file in case of single satellite solutions. :)

For versions 1 and 2 the involved satellites are indicated in the file names by a 2 digit identifier:
CHAMP        ... Ch
GRACE A      ... Ga
GRACE B      ... Gb
GOCE         ... Go
MetOpA       ... Ma
MetOpB       ... Mb
SAC-C        ... SA
Jason 1      ... J1
Jason 2      ... J2
TerraSAR-X   ... Te
TanDEM-X     ... Ta
Swarm A      ... Sa
Swarm B      ... Sb
Swarm C      ... Sc
C/NOFS       ... CN
COSMIC FM1-6 ... C1-6

Every solution is independent of any other solution.

!!! All solutons are only based on orbit positions (SST-hl) !!!

Please keep in mind: The quality of single satellite solutions can be quite different, depending on orbital height,
inclination, and data quality in general.

|-------------------------------------------------------------------------------------------------------------------|
|                          Processing strategy                                                                      |
|------------------------------------|------------------------------------------------------------------------------|
|Software:                           |  GROOPS (Gravity Recovery Object Oriented Programming System) developed at   |
|                                    |  the ITSG                                                                    |
|Observations:                       |  kinematic orbits (orbits are also accessible on the ftp archive)            |
|Estimation method                   |  Short arc integral approach (Mayer-Guerr T, 2006, Gravitationsfeldbestimmung|
|                                    |  aus der Analyse kurzer Bahnbögen am Beispiel der Satellitenmissionen        |
|                                    |  CHAMP und GRACE)                                                            |
|Permanent tide                      |  Solutions are tide free                                                     |
|-------------------------------------------------------------------------------------------------------------------|

All solutions are given as spherical harmonics coefficients and are saved in a gfc-file. In addition to the
coefficients also their standard deviations are given in the file.

No strict file naming convention anymore!