Subject: [IGSMAIL-5075]: Re: [IGSMAIL-5074]: New sites CHAN, IRKM
From: Jim Ray "(NGS" 301-713-2850 "x112)" <[email-masked]>
To: [email-masked]
Cc: [email-masked]
Date: Thu, 30 Dec 2004 09:54:52 -0500 (EST)

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IGS Electronic Mail      30 Dec 06:55:42 PST 2004      Message Number 5075
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Author: Jim Ray

Angelyn W. Moore wrote:
> ******************************************************************************
> IGS Electronic Mail      29 Dec 16:36:07 PST 2004      Message Number 5074
> ******************************************************************************
> 
> Author: Angelyn Moore
> 
> IRKM is in Irkutsk, Siberia, Russia and is managed by
> RDAAC-IMVP-JPL-LDEO ... please see the site log for details :)
> Data delivery is hourly and daily.  This receiver is attached
> to the same antenna as IRKT and may be considered to eventually
> replace the IRKT receiver (perhaps years from now).

With this addition, there are now 3 IGS stations in Irkutsk: IRKT (a
Rogue SNR-8000 receiver with D/M antenna), IRKM (a uZ12 receiver sharing
the same antenna and marker), and IRKJ (a JPS system at a different
marker).  IRKT is a reference frame station.  Each station possesses its
own distinctive advantages and disadvantages.

This circumstance (which also occurs at several other locations -- the
record is 5 stations at Wettzell) poses obvious questions for data analysts
as to which data set should be included in global solutions; it is not
generally possible for any group to analyze all possible data (now
approaching 400 stations).  Since most IGS products require multiple
solutions for the official combination, it is normally not possible for all
nearby stations to be utilized effectively.  In some cases, there is a
negative impact on IGS products when different ACs make different choices.

I thought this dilemma was resolved at the La Jolla workshop in 1999 with
the understanding that station operators can run as many GPS receivers as
they like (indeed, multiple receivers are strongly encouraged at fundamental
reference stations to ensure local stability, etc) but they should report
data only for one station confirmed to provide the "best" overall data set.
When a shift of operation from one main receiver to another is anticipated,
then a reasonable overlap period is indicated.  Unfortunately, this policy
has never been enforced.

If the IGS network is unrestricted in total numbers, then this issue is of
little general concern.  In that case, the ACs should informally decide
amongst themselves which data sets to process.  On the other hand, if the
IGS network is limited in number, which seems to be the case, then such
redundant stations are a very important concern.

In any case, there should be a clear, general policy about how such
situations should be handled.  If one site can have 5 IGS stations, should
all sites have that same right?  If only reference frame stations are
allowed to be redundant, how many is permitted at each?  It should be
evident that the present procedures are glaringly inadequate and even
counter-productive.

--Jim

[Note: My comments pertain to the general problem for the IGS and not to
Irkutsk specifically.]