[IGSMAIL-0817] Quality Check Programs

[W.]

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IGS Electronic Mail      Wed Dec 21 13:24:48 PST 1994      Message Number 0817
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Author: W. Gurtner
Subject: Quality Check Programs

IGS Data Quality Checks
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Dear colleagues,

at various IGS meetings and workshops the importance of a certain routine
quality check (qc) of the observational data was pointed out.

The general agreement was that such a quality check should be performed by
those agencies responsible for the stations, i.e. the Operational Centers or,
if there is no explicit OC, the stations themselves. 

Preferably such a quality check could be done immediately after conversion
of the raw data into RINEX.

Although there are several agencies that have developed and are routinely using
some sort of qc program it was felt that a standardized qc was highly
preferable, so that the results of the qc procedures could be made available
in a standard form to every user of the data.

A group at UNAVCO (Chris Rocken, Jim Johnson, John Braun) has developed
during the last years such a QC program that checks the data given in
RINEX observation and navigation message files. This program generates
some output on the standard output channel, a summary file per RINEX file,
and, optionally, a series of files for graphical visualization. At least for
PCs a graphics display program is available, too.

During the last few months Jim Johnson and myself have ported this QC program
to various platforms (UNIX: Sun-OS, Solaris, HP-UX, IBM-AIX; VMS: VAX, Alpha;
DOS: Microsoft Fortran Compiler, Lahey Compiler).

This program is now available as executables for the above-mentioned
platforms, together with a Users Guide (postscript file), a README file
and various auxiliary files on the IGS Central Bureau Information System:

   Internet :      igscb.jpl.nasa.gov
   User:           anonymous
   Directory:      /igscb/software/qc
   Subrirectories: dos, vms, unix, aux

The plans for the future are as follows:

-  Every Operational Center / Station runs a quality check program that
   creates (at least) a summary file per RINEX file, identical in contents
   and format as the one created by the UNAVCO program. The summary filenames
   are identical to the RINEX filenames, except the extension being ".yyS"
   (yy: year).
   
   This qc program could be the UNAVCO QC program or any program fulfilling
   these requirements. The UNAVCO QC program could also run in addition to
   the other qc program.

-  The results of the qc program can be used to (automatically) decide if the
   data are forwarded to the IGS network or not.

-  The summary files accompany the RINEX observation and navigation message
   files on their flow through the IGS network and are thus available
   at the respective Data Centers.

-  Using the one-line summary within each summary file it is easy for everybody
   to generate ("grep") a condensed overview over all files.

Before we can install such a procedure we need a phase to come to an agreement
on the proposed summary file:

May I ask all Operational Centers, IGS Stations or other interested parties:

- to get from the IGS Central Bureau Information System the sample summary file
  (/igscb/software/qc/aux/ZIMM1700.94S), the postscript QC Users Guide
  (qc.ps) and the README.QC file, and to check if your qc program could
  be modified to generate such a summary file, too

or

- to get from the IGS CBIS the UNAVCO QC program for your platform(s) and test
  it extensively with data from your stations

and

- to send back any proposals for (hopefully moderate) modifications of the
  summary file format (mail to IGSCB at IGSCB.JPL.NASA.GOV).

We will then review the proposed modifications and try to come up with a
final summary file format.

If you have questions about the installation of the programs please do not
hesitate to contact me at GURTNER at AIUB.UNIBE.CH.


December 21st, 1994                                         Werner Gurtner


[Mailed From: Werner Gurtner <GURTNER at aiub.unibe.ch>]