[IGSMAIL-2086] Summary of the IGS Network Workshop, 2-5 November 98

Ruth Ruth
Sat Nov 28 15:08:13 PST 1998

IGS Electronic Mail      Sat Nov 28 15:08:13 PST 1998      Message Number 2086

Author: Ruth E. Neilan
Subject: Summary of the IGS Network Workshop, 2-5 November 98

                        Summary Notes
              The 1998 IGS Network System Workshop
                      November 2-5, 1998,
                      Annapolis, Md, USA

Dear colleagues,

Nearly 100 IGS colleagues gathered November 2 - 5 to attend a workshop
dedicated to the infrastructure of our collaborative international
organization. The IGS has been an operational service for nearly five
years, providing GPS data and products from a globally distributed network
of high precision GPS receivers to our internal users, especially the
Analysis Centers, as well as to numerous external users. Since the
inception of the IGS, we have not sponsored a  workshop of this type,
focusing on the network issues and how future planning of the IGS affect
and are critically dependent on the foundation of the network. This
workshop provided a great opportunity for people working within the various
components of the IGS to meet and discuss current configurations, problems
and resolutions. A good deal of time was devoted to understanding the many
future requirements and how to begin incorporating these into our existing
infrastructure. One of the key shifts in the IGS network is the realization
of emerging application networks, e.g., a subset of the IGS network is used
for ITRF, a different subset has the characteristics to support precise
time transfer, yet another may meet the requirements defined for support to
the LEO missions, etc.  This is a theme that was raised in nearly each
position paper.

The final day of the workshop, Nov. 6 was a summary session for the program
committee to pull together the summary recommendations of the workshop.
These will be reviewed by the Governing Board at its December meeting and
approval sought for the appropriate recommendations. A proceedings of the
workshop is in progress and will be available on the CBIS website as well
as in limited hardcopy publications. The final result of the workshop is
intended to become a Network Operations Plan for the IGS Network System.

In brief, the workshop was considered to be productive and engaging, both
in the workshop meetings as well as during the discussions, breaks, social
receptions and dinners. Carey Noll put a tremendous amount of effort into
the local organization of the workshop and it was a total success. We are
all indebted to her for her dedication and positive attitude in everything
she does. Thanks are also due to her staff for making the whole event

Acknowledgments and thanks to those contributing to this summary message:
Jan Kouba, Carey Noll, and Angelyn Moore.

A more detailed day by day summary follows below:

Day 1

The first day was devoted to bringing the attendees together to focus on
the status of the IGS, current performance issues and future requirements.
The welcome was given by Dr. Clark Wilson from NASA headquarters, the
funding sponsor of the workshop, and followed by Dr. Vince Salmonson,
Director of the Earth Sciences Division at GSFC, which includes local
organizing institution of the workshop, the CDDIS.

Prof. Gerhard Beutler provided an excellent keynote summary of the 'State
of the IGS', stressing the important contribution of the improving and
expanding IGS network, as well as the wealth of information in past IGS
data. He pointed out that the IGS Network is the combining element of all
space geodetic networks. He also showed the importance of complete and
correct station information for daily analyses as well as for historical
data in the very likely event of future reprocessing of the datasets.

The workshop was fortunate to have many representatives present from the
Analysis Centers, and it was exceptional that the Analysis Center
Coordinator, Jan Kouba could personally attend and participate in the whole
workshop.  The link between the network and the ACs must be strengthen and
this workshop was a good attempt in promoting stronger connections. The
second key talk, 'Current Network Performance', was given by Dr. James
Zumberge, with co-authors Kouba, Springer and Gurtner was therefore
extremely relevant. Some of the key points and recommendations that stem
form this position paper were to highlight previous AC discussions and
conclusions in regards to discrepancy resolution, improved and consistent
naming conventions and the need for clear guidelines at all levels of IGS
operations. The need for instructions on how to make and document hardware
changes to ensure the continuity of station solutions by the ACs was
emphasized. The usefulness of network monitoring tools, e.g., the IGS.net
analysis, was acknowledged and more detail metrics on data noise was
suggested both here and again in subsequent discussions as a future

After a break, presentations on the future of GPS and Future Requirements
followed. We were fortunate to have David Minkel, Deputy Director of the
NGS, to speak to us on 'GPS Modernization', the future GPS space systems.
Minkel is very involved in civilian side of planning the dual-use
enhancements to the future GPS space systems.  He noted that the third
frequency is converging on the region of 1181 MHz, that Block II's are
lasting longer than expected, which in fact may delay the implementation of
the new satellites with the third frequencies by a few years. Also that the
US military is now considering a new and improved signal structure and
possibly leaving the original (less precise/robust P/Y code) to civilians.

The future requirements session was comprised of an excellent panel
speaking for the future needs, requirements and optimization of the IGS.
Overviews were given by the IGS projects for tropospheric, ionospheric,
timing, and Low Earth Orbiter applications. Additional presentations
included an overview of the IGEX (International GLONASS EXperiment) and its
current status by Jim Slater. Seth Stein, the newly appointed Scientific
Director of UNAVCO, gave an update on plate tectonics and noted that the
IGS is responsible for providing the global framework that so much of the
science depends on.  A subsequent presentation by Frank Webb, Chair of the
SCIGN GPS Board underscored the rapid densification of regional arrays and
began to address how the IGS can develop an interface with these regional
networks. Real time application perspectives and communication issues were
pointed out by Mike Whitehead of Satlock Corporation.

Day 2

On Tuesday morning, the Physical Site specification and Communication and
Data Links were scheduled. In the first session, chaired by W. Gurtner,
presentations were made on monumentation, site selection, multipath
detection, status/updates of Hatanaka compression and two antenna related
presentations. It was noted physical monumentation and its' description in
the site log could be improved. A number of global IGS stations are roof
top installations, and even for properly (geodetically) monumented points,
the monument related site log entries are often rather sparse and
inadequate. The site specification session ended with a consensus that a
unique and consistent file naming must be developed and adhered to for site
logs, station data files (RINEX), and station solutions files (SINEX). All
should be based on a unique (and officially adopted) 4 character station
name identifier. There was some discussion of the proposal forwarded by the
ACs and it was recommended that the data centers and interested network
people respond to this scheme to resolve any remaining issues, by proposing
alternative approaches. Werner Gurtner agreed to handle the discussion on
this issues by email and compile the suggestions with the goal to reach
some resolution by the end of the year.

The next session was devoted to 'Benchmarking' the IGS Network. It has been
noted that the IGS communication paths are not as efficient as they could
be. It was pointed out that ACs have to shop frequently at many DCs to
retrieve data fast enough for the rapid products.  To this end the Central
Bureau and the Infrastructure Committee, with technical assistance by
UNAVCO, have been working on a questionnaire to map the communications and
data flow of the IGS network.  By understanding the characteristics of the
current network configuration, we can work to develop more efficient paths
and methods to support the ACs. The consensus seems to be developing that
data 'pushes', from the lowest levels all the way up to Dcs and ACs may be
a more efficient approach to data distribution.

In the afternoon the newly designed and expanded IGS CBIS WWW site was
demonstrated. It was agreed that it is a very useful improvement over the
original stie. A few minor improvements were suggested and everyone is
encouraged to explore the site and provide comments and suggestions.

A long poster session was held in the afternoon with lots of time for
people to discuss on an individual basis. A reception with great food and
drink was hosted by the people at Ashtech, many thanks to Robert Snow.

Day 3

Data center issues began the day and a number of issues were raised: SIO's
concentrated effort to clean up past records, site information, etc.; the
Seamless Archive approach. However, there was considerable discussion on
the list of recommendations from the ACs on how to deal with inconsistent,
non-compliant, or 'bad', poor quality data. The ACs want to exclude such
data from their analyses, as it corrupts the solution and is difficult for
them to deal with.  The DCs, with Carey Noll and Jeff Dean in the lead,
agreed to investigate the situation and develop an approach that would help
to ease the ACs processing. The ACs have proposed separate data
directories, and the DCs did not agree with this concept and would like to
devise different solution.

The network monitoring session was chaired by Neilan and Moore, and most
time was devoted to discussion. The CB is committed to resolving the data
discrepancies and consistency problems and plan to improve quality
monitoring in conjunction with regional network managers. It was noted that
each IGS agency must be responsible for the validity of their information,
and that the CB could monitor and respond, but that each agency has the
ultimate control. Updating of site logs and where the logs should reside in
order to minimize future problems was also discussed. Consensus was that
appropriate software tools (such as an automatic site log generation and
editing program) should be developed and used at the lowest level possible,
closely monitored and assisted by the Network Coordinator at the CB. The
challenge to eliminate the data discrepancies and incomplete information by
the end of 1998 was issued by Ruth Neilan. (Errors & inconsistencies files
were posted and individual stations were challenged to come forward with
corrections as soon as possible).

In the late afternoon, the Network Upgrade Panel addressed network
enhancement issues and GPS instrumentation. Bock presented a compelling
case demonstrating that even mundane changes, such as antenna
reinstallation/antenna replacements (of the same type) can create
significant (mm) changes. It was argued that a significant subset of the
IGS stations (e.g. the 47 ITRF stations) should receive special care. It
was emphasized repeatedly that IGS needs clear guidelines how to manage
past, present and future hardware changes so that solution step functions
are mitigated.

The last session was devoted to the GLONASS and GPS manufacturers (3S,
Trimble, AOA, Javad, Ashtech and Leica). All assured that Y2K and Wk 1024
problems will be tested and by early next year firmware upgrades (if
necessary) will be distributed to users (free of charge). The newest
receiver and antenna demonstrated to the IGS was the Javad which seems to
include a few innovations, such as a new choke ring design, with separately
tuned for L1 & L2 (somehow electronically), a newly design, 40 Channel
GPS/GLONASS receiver with tracking aiding -- a high elevation SV aids the
low elevation SV tracking, purportedly increasing the low elevation SNR by
10 Db!

Jan Kouba has pointed out that while he was listening to the receiver
people, showing how every one is nowadays supplying 6 pairs of observables
(code and phase on C/A, P1 and P2) it occurred to him that the IGS
currently has a problem. Namely that the Turbo Rogues (the vast majority of
receivers in the IGS network) under AS give C/A and (C/A + P2-P1) instead
of P2, and that, we cannot match this pair with any of the above 3 pairs.
The implications are inconsistencies/incompatibility (at 1-2 ns level) in
the satellite clock solutions and L1_L2 satellite calibration biases.
Clearly this needs to be thought through and IGS should make some decision
for current and future hardware updates. This was discussed with some
hardware people and clarification/confirmation on what specific receivers
exactly output should be forthcoming, and hopefully soon.

On Wednesday night the group was graciously hosted by Leica for a guided
one-hour historical candlelight tour of Annapolis, led by several Annapolis
women in authentic 17th century dresses, and with the full moon rising.
This was followed by a banquet dinner at the authentic Price House of
Annapolis. Many thanks to the folks at Leica for providing such an
enjoyable social event, Tom Stansell and James Stowell.

Day 4

On Thursday, the new communication technology of next generation Internet
and the STARTAP network were presented by Steve Goldstein, Director at the
National Science Foundation of the Networking and Communications Division.
Currently some fast connections devoted to research and education are
already globally available. It was suggested to talk to your ISP to explore
the possibility of being connected. Steve's slides will be included in the
proceedings. In the second presentation, a private communication
consultant, Greg Peisinger, concentrated mainly on getting data from
stations via various communication techniques, as well as the real time

The workshop ended by working group discussions: Physical sites, Data
Centers, Network Upgrades (including communications and future
requirements) & Network Monitoring. After lunch, the leaders of each of the
above 4 groups presented group recommendations & conclusions for the forum

The Physical Site groups recommendations included the outstanding issue of
the unique 4 character ID, and as noted above, it was taken upon by the
group leader, Werner Gurtner. Also recommended was rigorous standardization
of site log formats and time stamping of site logs, with incorporation into
the SINEX files.

The Data Center group presented a list which included the need for
developing DC guidelines, immediate site log updates (hours not days),
planning for handling and use of hourly data, a commitment to look into the
flagging of data considered non-compliant or 'bad' by ACS, and to work with
the CB to develop the station functional characteristic matrix (identifying
what IGS stations may meet requirements for various applications).

Network Monitoring also presented a set of recommendations, including team
& community building, noting that most problems stem from lack of
communication thus focusing on the need for improving communications
amongst DC/AC and IGS station managers. 'Accreditation' or re-registering
of IGS stations should be considered. The group also supported the
'challenge' by CB to eliminate station discrepancies.

The Network Upgrade group suggested that a selected subset of important
stations be systematically updated with 'homogenous' hardware and that
these sites have two 'hot' installations which are established and
analyzed. This created a great deal of discussion that was impossible to
resolve in the short time remaining, it was recommended that the
Infrastructure Committee should perhaps prepare a proposed plan on how to
approach this issue.

Day 5
Friday morning was a summary session for the program committee and the
session chairs. Neilan encouraged Kouba to begin by presenting the 'AC
shopping list' (i.e., the recommendations of the Zumberge et al. position
paper presented on Monday). It was not completely included in the context
of the established panels and discussion groups and it is important for the
AC considerations and suggestions to be addressed.

Each panel moderator again presented the final recommendations of each
group and these will be widely distributed after the Governing Board
meeting on December 6.

At this time, it is most appropriate to thank the program committee,
session chairs and panel members for a job well done. Many thanks to all
the contributors and participants.  A very special and heartfelt thanks
goes to Carey Noll and her staff for their outstanding local organization
and attention to detail.  The workshop was a wonderful experience for all
who attended and has produced many sound recommendations for the inevitable
improvement of the future IGS network.


Ruth Neilan

Ruth E. Neilan                    Telephone:     (818)-354-8330
Director, IGS Central Bureau      FAX:           (818)-393-6686
Jet Propulsion Laboratory         E-mail (IGS):  igscb at igscb.jpl.nasa.gov
MS 238-540                        E-mail:        ruth.neilan at jpl.nasa.gov
4800 Oak Grove Drive              E-mail (alternate):
Pasadena, CA 91109                          rneilan at tonga.unavco.ucar.edu

               World Wide Web:  http://igscb.jpl.nasa.gov/

                      Secretary: Carol Lorre
         tel: 818-354-2077   email: <carol.lorre @jpl.nasa.gov>

[Mailed From: "Ruth E. Neilan" <rneilan at mail1.jpl.nasa.gov>]

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