[IGSMAIL-5008]: Some information on the error codes given in the sp3-c

[Gerd Gendt]

******************************************************************************
IGS Electronic Mail      07 Sep 07:29:24 PDT 2004      Message Number 5008
******************************************************************************

Author: IGSACC

Dear IGS Community,

We would like to give some explanation how the error codes
inserted into the sp3-c are computed.

1. The summary error-codes given in the header for x,y,z are
   identical with those in the sp3-a

2. The epoch error codes for the clocks are taken directly 
   from the *.clk file for Rapid and Final products.
   For Ultra Rapid products they are taken from the computation
   of the weighted mean of the n AC values at each epoch: 
      standard deviation of AC epoch values / sqrt(n)
      or more specific
      sqrt[ sum(Wi*(Xi - weightedMean)**2 )/((n-1)*sum Wi )]

3. The epoch error codes for x,y,z are also taken from the 
   computation of the weighted mean of the n AC values at each epoch: 
      standard deviation of AC epoch values / sqrt(n) 
   
The epoch-wise error codes will provide a time dependent assessment
of the product quality. By them you can easily see the growing error
of the predictions with time, and the larger errors for the orbits
at the day boundaries. 


Best regards

Gerd Gendt 
Thomas Nischan

******************************************************************************
*                         Gerd Gendt                                         *
*  _/_/_/  _/_/_/_/_/_/   GeoForschungsZentrum                               *
* _/       _/       _/    Department Geodesy and Remote Sensing              *
* _/ _/_/  _/_/    _/     Telegrafenberg A17                                 *
* _/    _/ _/     _/      D-14473 Potsdam ,  GERMANY                         *
*  _/_/_/  _/    _/_/_/   Phone : ++49 331 288 1114   Fax :++49 331 288 1759 *
*                         E-Mail: gendt at gfz-potsdam.de                       *
* IGS GFZ AC         :    AFTP://ftp.gfz-potsdam.de/pub/igsprod              *
*                         http://www.gfz-potsdam.de/igs                      *
* IGS Analysis Coord.:    AFTP://ftp.gfz-potsdam.de/pub/igsacc               *
*                         http://www.gfz-potsdam.de/igsacc                   *
******************************************************************************