GPS World, September 2018

mail services are hosted www igs org The CB also represents the outward face of IGS to a diverse global user community as well as the general public The CB office is hosted at the California Institute of Technology Jet Propulsion Laboratory in Pasadena California It is funded principally by the U S National Aeronautics and Space Administration NASA which generously contributes significant resources to advance the IGS The IGS Network The foundation of the IGS is a global network of more than 500 permanent and continuously operating stations of geodetic quality These stations track signals from GPS and increasingly also track signals from GLONASS Galileo BeiDou the Quasi Zenith Satellite System QZSS the Indian Regional Navigation Satellite System IRNSS also known as NavIC Navigation with Indian Constellation as well as space based augmentation systems SBAS FIGURE 1 shows the recent state of the IGS network indicating which stations are GPS only GPS GLONASS and multi GNSS FIGURE 2 is a photo of the IGS station ARHT at McMurdo Station Antarctica The IGS is a critical component of the IAGs Global Geodetic Observing System GGOS where it encourages and advocates for geometrical linkages of GNSS with other precise geodetic observing techniques including satellite and lunar laser ranging very long baseline interferometry and Doppler Orbitography and Radio Positioning Integrated by Satellite DORIS These linkages are fundamental to generating and accessing the ITRF Data and Analysis Centers Lots of hard work and dedication from IGS contributing organizations goes into the fabrication of IGS products which start at the tracking network then are collected by data centers and sent to analysis centers At these centers the data are compared and combined by the analysis center coordinator and finally made available as IGS products The IGS ensures high reliability by building redundancy into all of its components In 1994 the IGS started with a network of about 40 stations today more than 500 receivers are included in the network Critical to this activity are three categories of data center operational regional and global At the ground level are operational data centers which are in direct contact with IGS tracking sites and are responsible for such efforts as station monitoring and local archiving of GNSS tracking data Operational data centers also validate format exchange and compress data Regional data centers then collect tracking data from multiple operational data centers or stations maintaining a local archive and providing online access to their data The six global data centers www igs org about datacenters receive retrieve archive and provide online access to tracking data from operational and regional data centers These global data centers are also responsible for archiving and backing up IGS data and products and maintaining a SEPTEMBER 2018 WWW GPSWORLD COM GPS WORLD 51 A QUARTER OF A CENTURY That is how old the International GNSS Service IGS will be on Jan 1 2019 Conceived in the early 1990s as the International GPS Service for Geodynamics the IGS continues to be the global standard bearer in providing receiver data satellite orbit and clock products and other resources with the highest possible precision and accuracy I remember the discussions that took place at international conferences about the need for such a service to provide the necessary data to advance our understanding of plate tectonics and other Earth related phenomena And this was well before GPS was officially declared fully operational in 1995 Remember surveyors and geodesists were early adopters of GPS making use of the technology even when only a partial GPS constellation was in place The initial ideas for the IGS were laid out in an article published in GPS World in February 1993 entitled Geodynamics Tracking Satellites to Monitor Global Change But the services provided by the IGS extended well beyond the needs of the geodynamics research community and so its name was shortened to just the International GPS Service When GLONASS data and products became available the name was further changed to its current moniker One of the IGSs notable achievements has been in advancing GNSS standards such as the Receiver Independent Exchange format for receiver data and other information The need for such a standard was clear even before the formation of the IGS and it was documented in this column in the July 1994 issue of GPS World RINEX The Receiver Independent Exchange Format We continued to cover the evolution of the IGS over the years with for example the article The International GNSS Service Any Questions in the January 2007 issue of the magazine And now as Galileo BeiDou the Quasi Zenith Satellite System the Indian Regional Navigation Satellite System and a variety of satellitebased augmentation systems join GPS and GLONASS we help celebrate the coming 25th anniversary of the IGS as a truly multi GNSS service INNOVATION INSIGHTS BY RICHARD B LANGLEY