Global Positioning System Reference
In-Depth Information
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and security at the same time. There are eight analysis centers. These centers are the
scientific backbone of the IGS that use the global data sets to produce products of
the highest quality. The analysis centers cooperate with an analysis center coordina-
tor, whose main task is to combine the products of the centers into single product,
which becomes the official IGS product. The global data centers and central bureau
make it available. The analysis centers are: (1) Astronomical Institute University of
Bern, Center for Orbit Determination in Europe, Switzerland; (2) European Space
Agency/European Space Operations Center, Germany; (3) GeoForschungsZentrum,
Potsdam, Germany; (4) NASA Jet Propulsion Laboratory, California Institute of
Technology, United States; (5) National Geodetic Survey, National Oceanic and At-
mospheric Administration, United States; (6) Natural Resource, Canada; (7) Scripps
Orbit and Permanent Array Center, Scripps Institution of Oceanography, United
States; and (8) U.S. Naval Observatory, United States.
Detailed information about the IGS is available at the website (IGS, 2002). A
strategic plan for the years 2002-2007 found at that website lists the long-term goals
and objectives of the IGS:
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Provide the highest-quality, reliable global navigation satellite system (GNSS)
data and products openly and readily available to all user communities.
Promote universal acceptance of IGS products and conventions as the world
standard.
Continuously innovate by attracting leading-edge expertise and pursuing chal-
lenging projects and ideas.
Seek to implement new growth opportunities while responding to changing user
needs.
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Sustain and nurture the IGS culture of collegiality, openness, inclusiveness, and
cooperation.
Maintain a voluntary organization with effective leadership, governance, and
management.
The various IGS products are summarized in Table 7.1. These products have become a
de facto world standard for many GPS applications. Examples of universally accepted
formats include receiver independent exchange format (RINEX), standard product
#3 for ECEF (earth centered earth fixed) orbital files (SP3), and solution independent
exchange format (SINEX).
7.2 ANTENNA CORRECTIONS
It is important that the GPS signals are treated/modeled correctly at the satellite and at
the receiver. We discuss the phase windup correction and how to deal with the separa-
tion of satellite antenna phase and satellite center of mass. The receiver phase center
offset and variation is generally dealt with in terms of relative and absolute antenna
calibration. Several examples are given to shed light on the nature of signal multipath.
 
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