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General concept of VieVS

The VieVS software has been written by the Research Group Advanced Geodesy at the Department of Geodesy and Geoinformation (GEO), Vienna University of Technology. It includes state of the art models that coincide with the latest International Earth Rotation Service (IERS) conventions. It is written in Matlab (version 8.4-R2014b or later is required) which has the advantages of being easy to use and source code changes can be applied without much effort. Unfortunately Matlab is expensive and is not as fast as C++ or FORTRAN. Matlab is, however, widely used, hence many research facilities are already in possession of a licence. The slower speed is not a big disadvantage since today's computer hardware is fast enough for normal usage of the software.

The VieVS software is structured in different parts:

Different modules of VieVS and their relation

  • The fi rst part, VIE_INIT (INIT stands for initialising), is responsible for reading the data; currently VieVS needs session files ( files with the actual measurements) in NGS format or VGOSDB databases. Data created here is saved in the LEVEL 0 folder.
  • The second part, VIE_MOD (MOD stands for modelling), calculates the theoretical delays, and its partial derivatives, models according to the IERS conventions are implemented. Data created here is saved in the LEVEL 1 folder.
  • The third part, VIE_LSM (LSM stands for least squares matching), is responsible for the least squares estimation. Parameters such as EOPs, station coordinates and clock offsets etc. are estimated and saved in the LEVEL 3 folder for further investigation.

Apart from the main structure in VieVS there are three other modules, namely VIE_SCHED, VIE_SIM and VIE_GLOB.

  • VIE_SCHED (SCHED stands for scheduling) is the scheduling package of VieVS. With this module an observation plan for a specif ic time and network can be created. It is also possible to write a NGS format file as output which can then be simulated and analysed with the main VieVS methods.
  • VIE_SIM (SIM stands for simulating) creates simulated observations for an observation plan (could either be from a real session or scheduled). It combines the theoretical delay with simulated values for zenith wet delay, clocks and observation noise at each epoch, in order to create realistic observations. The output is saved as NGS format and can then be analysed with the main VieVS methods.
  • VIE_GLOB (GLOB stands for global) combines the normal equations of several sessions into a global solution in order to calculate reference frames and global parameters.

Parameters and models can be easily selected using the graphical user interface (GUI) of VieVS. The output is written to the command window of Matlab or, for some modules, in log files. The results are saved as Matlab files or text files.

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public/vievs_manual/general_concept_of_vievs.txt · Last modified: 2017/09/05 11:30 by mschartn