they 
994]. 
. that 
tation 
to the 
define 
nation 
ange. 
1 and 
as of 
d as 
. that 
ervice 
)pliers 
ad of 
olithic 
comes 
lea is 
jy the 
6]. It 
razor: 
re). A 
tation 
Je: An 
Part 1 
cation 
C, 35 
1778. 
iption: 
Data 
ational 
iences 
ational 
de 
Vienna, 
phone: 
email: 
Establishing Global and Regional Geodetic Reference Frames: 
The International GPS Service for Geodynamics 
Ivan I. Mueller (The Ohio State University, Columbus), 
James F. Zumberge, Ruth. E. Neilan (Jet Propulsion Laboratory, California Institute of Technology), Gerhard Beutler, 
Werner Gurtner (University of Berne) 
KEYWORDS: International Service, GPS, Reference Frames, Orbits 
ABSTRACT 
The International GPS Service for Geodynamics is an international scientific service which began formal operation at the 
beginning of 1994, following several years of planning [1] and a 11/5-year pilot service. The IGS collects, archives, and 
distributes GPS observation data sets, and uses these to generate high accuracy GPS satellite ephemerides, earth rotation 
parameters, coordinates and velocities of the IGS tracking stations, GPS satellite and tracking station clock information, and 
atmospheric information. 
To accomplish its mission, the IGS consists of a network of GPS tracking stations, Data Centers, Analysis Centers, an 
Analysis Coordinator, a Central Bureau, and a Governing Board. The accuracies of IGS products are sufficient to support 
current scientific objectives, including the realization of the International Terrestrial Reference Frame (ITRF), monitoring of 
the earth's rotation and deformation of its liquid and solid components, ionsopheric monitoring, and scientific satellite orbit 
determination. A Central Bureau Information System (CBIS) allows public access to IGS products, which include precise 
GPS ephemerides within 2-3 weeks of real time. IGS contributors and customers communicate through electronic mail, and 
exchanges are archived for future reference. 
INTRODUCTION 
The primary objective of the International GPS Service coordinates and velocities of the IGS tracking stations, 
for Geodynamics is to provide a service to support, GPS satellite and tracking station clock information, and 
through GPS data products, geodetic and geophysical ionospheric information. 
activities. Cognizant of the immense growth in GPS 
applications the secondary objective of the IGS is to In particular the accuracies of these products are sufficient 
support a broad spectrum of operational activities for the improvement and extension of the International 
performed by governmental or commercial Terrestrial Reference Frame (ITRF) maintained by the 
organizations. The service also develops the necessary IERS, the monitoring of solid earth deformations, the 
standards and specifications and encourages international monitoring of earth rotation and variations in the liquid 
adherence to it's conventions. earth (sea level, ice-sheets, etc.), for scientific satellite 
orbit determinations, and ionosphere monitoring. 
À proof of concept for the International GPS Service for 
Geodynamics was conducted with a three-month To accomplish its mission, the IGS consists of a network 
campaign during June-September 1992 [2], and was of GPS tracking stations, several Data Centers, Analysis 
continued through a pilot service until the formal Centers, an Analysis Coordinator, a Central Bureau, and a 
establishment of the IGS in 1993 by the International Governing Board. 
Association of Geodesy (IAG). The routine IGS started on 
January 1, 1994. IGS operates in close cooperation with OPERATION OF THE IGS 
the International Earth Rotation Service (IERS). The IGS 
Terms of Reference [3] describes in broad terms the goals The IGS global network today comrises of about 100 
and organization of the IGS. stations with GPS tracking receivers. Within the next few 
years, expansion of the global network will address the 
The IGS collects, archives, and distributes GPS paucity of sites near longitude 90°E, with planned 
observation data sets of sufficient accuracy to satisfy the coverage in Central Asia and islands in the Indian Ocean. 
objectives of a wide range of applications and Regional densification networks are also being tied to the 
experimentation. These data sets are used by the IGS to ITRF system, especially in the Arctic, Australia, Europe, 
generate data products, including high accuracy GPS East Asia, Japan, South America and the U.S. 
satellite ephemerides, earth rotation parameters, 
63 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996