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IGS Terms of Reference (v. 02/2017)



Adopted February 2017

This article is available for download in .pdf format at the bottom of this page.


A proof of concept for the International Global Positioning System (GPS) Service for Geodynamics (IGS) was conducted with a three-month campaign during June through September 1992, and continued until December 1993 as a Pilot Service until the establishment of the IGS as a service of the International Association of Geodesy (IAG). The IGS formally began on 1 January 1994. IGS operates in close cooperation with the International Earth Rotation and Reference Systems Service (IERS). As a result of the review of IGS objectives, the name of the service was changed to International GPS Service (IGS) on 1 January 1999. Following further expansion of IGS, integrating data from the Russian GLONASS system and from future Global Navigation Satellite Systems, the name was changed to "International Global Navigation Satellite Systems (GNSS) Service" on 14 March 2005, in the scope of an update of the Terms of the Service. The organization retains the acronym "IGS". Developments in the intervening period necessitated a further update of these Terms of Reference in 2010[i], 2014[ii] and in 2017[iii].


The International GNSS Service provides, on an openly available basis, the highest-quality GNSS data, products, and services in support of the terrestrial reference frame; Earth observation and research; Positioning, Navigation and Timing (PNT); and other applications that benefit the scientific community and society.


The IGS goals and objectives are articulated within its Strategic Plan, which is reviewed and updated by the Governing Board nominally every 4 years. Generally, the IGS strives to:

  • Serve as the premier source of the highest-quality GNSS related standards and conventions, data and products, openly available to all user communities.

  • Attract leading-edge expertise to pursue challenging, innovative projects in a collegial, collaborative and creative culture.

  • Incorporate and integrate new systems, technologies, applications and changing user needs into IGS products and services.

  • Facilitate the integration of IGS into GGOS and other more broadly based Earth observing and global navigation systems and services.

  • Maintain an international federation with committed contributions from its members, and with effective leadership, management and governance.

  • Promote the value and benefits of IGS to society, the broader scientific community, and in particular to policy makers and funding entities.


The IGS collects, archives and distributes GNSS observational data sets of sufficient accuracy to satisfy the objectives of a wide range of applications and experimentation. These data sets are used by the IGS to generate the following data products:

  • High accuracy GNSS satellite ephemerides and related information

  • Earth rotation parameters

  • Coordinates and velocities of the IGS tracking stations

  • GNSS satellite and tracking station clock information, timescale products

  • Ionospheric information

  • Tropospheric information

The accuracies of these products are sufficient to support scientific objectives including:

  • Realization of global accessibility to, and the improvement of, the International Terrestrial Reference Frame (ITRF)

  • Monitoring deformation of the solid Earth

  • Monitoring Earth rotation

  • Monitoring variations in the hydrosphere (sea level, ice sheets, etc.)

  • Scientific satellite orbit determination

  • Ionosphere monitoring

  • Climatological research, and eventually weather prediction models

  • Time and frequency transfer


The IGS accomplishes its mission through the following components:

  • Networks of tracking stations

  • Data Centers (DCs)

  • Analysis and Associate Analysis Centers (ACs, AACs)

  • Analysis Center Coordinator (ACC)

  • Working Groups, Pilot Projects (WG, PP) and Committees

  • Coordinators for products or components, e.g., Reference Frame, Network, Real-time, Timing, etc.

  • Central Bureau (CB)

  • Governing Board (GB) and Committees (Executive Committee (EC), Infrastructure Committee (IC), Elections Committee, Associates Committee)

  • Associate Members


IGS stations provide continuous tracking using high accuracy receivers and have data transmission facilities allowing for rapid (minimally: daily) data transmission to the data centers (see below). The stations must meet physical and operational requirements as defined in the "IGS Site Guidelines" document available from the CB and published on the IGS website ( The ensemble of the IGS stations is the IGS network.


IGS data centers fall into three categories: Operational, Regional, and Global Data Centers (DCs). Each has varied duties which must be carried out continually and with a minimum of delay or downtime, although the multiplicity of DCs provides a measure of redundancy. The description and responsibilities of each type of DC are detailed in the separate policy document "Charter for IGS Data Centers" and include duties such as collecting data from GNSS tracking stations and ancillary equipment, data validation, permanent archival, providing online availability, and transmittal to and equalization with other DCs. The set of DCs provides for open access to IGS data and products by IGS participants and all external users. DCs are approved by the IGS GB following demonstration of qualifications and commitment.


The analysis centers fall into two categories: Analysis Centers (ACs) and Associate Analysis Centers (AACs). The analysis centers receive and process tracking data from one or more data centers for the purpose of producing IGS products. The ACs are committed to submit products for combination into IGS products, without interruption, using designated standards and conventions, and within a specified time delay to meet IGS requirements. The ACs generally provide the core products of ephemerides, Earth rotation parameters, station coordinates, and clock information, as well as other recommended products, such as rapid, predicted or real-time orbit and Earth rotation solutions. AACs produce specialized products recognized by the GB, e.g., ionospheric information, tropospheric parameters, or station coordinates and velocities for a global or regional sub-network.

The "Charter for IGS Analysis Centers and Associate Analysis Centers" is a policy statement of the GB and is available from the CB and from the IGS website (


The Analysis Center Coordinator assists the ACs and monitors their activities to ensure that the IGS objectives are carried out. Specific expectations include quality control, performance evaluation, and continued development of appropriate analysis standards. The Analysis Center Coordinator is also responsible for the appropriate combination of the ACs’ products into a single set of orbit and clock products, which are official IGS products delivered to the Global Data Centers.

The Analysis Center Coordinator is a voting member of the IGS GB (see below) and interacts regularly with the CB and the IERS. The Analysis Center Coordinator (or designee as approved by the GB) is one of the two IGS representatives to the IERS Directing Board.

Generally the responsibilities for the Analysis Center Coordinator shall rotate among the ACs with appointments and terms specified by the GB.


A Working Group works on a particular topic related to the IGS mission according to goals and schedule specified in the Working Group’s charter. A Pilot Project aims at the development of new IGS product(s) relying on the IGS infrastructure. A Product Coordinator is responsible for a specialized product related to the IGS missions and components, as set out in its charter. Each Product Coordinator is supported by a Working Group, whose members take responsibility for providing routine contributions to a combined product, and/or make expertise available to the Working Group.

The GB establishes and terminates Working Groups and Pilot Projects, and appoints the Working Group and Pilot Project Chairs and Product Coordinators. A minimum initial commitment for any Product Coordinator is four years. The document "Policy for the Establishment of IGS Working Groups, Pilot Projects and New Operational Products" is a policy statement of the GB and is available from the CB and the IGS website (

Chairs of Committees, Special Projects, Working Groups, and Pilot Projects are non-voting members of the IGS GB (see below). The Coordinators of the core products shall be voting members of the Board (Analysis Center Coordinator, Reference Frame Coordinator, Real-Time Analysis Coordinator, Timing Coordinator).

In the case of products requiring significant joint expertise, the GB may approve GB membership of a representative of a partner organization, in order to ensure appropriate representation and communication. Such a representative is designated by the partner organization and is a non-voting member of the GB. It will normally be expected that the GB will in turn be invited to appoint an IGS representative to the Directing Board, or equivalent body, of the partner organization.


The Central Bureau (CB) is the executive arm of the IGS GB, responsible for the general management, coordination and day-to-day operations of the IGS consistent with the directives, policies and priorities set by the GB. In this role the CB, within available resources, coordinates IGS activities, facilitates communications, coordinates general aspects of the IGS network operations, promotes compliance to IGS standards, monitors network operations and quality assurance of data, maintains documentation, organizes meetings and workshops, and coordinates and publishes reports.

The CB actively coordinates with the IGS Pilot Projects, Working Groups, Product Coordinators, and committees and ensures the compatibility of IGS and IERS by interfacing with the IERS. The CB acts as the outreach office and promotes use of IGS data and products, maintaining and expanding the visibility of the IGS.

The CB operates the information system for the IGS and produces the IGS Annual Reports and Directory. The CB coordinates the publication of other documents required for the satisfactory planning and day-to-day operation of the Service, including standards and specifications regarding the performance, functionality and configuration requirements of all elements of the Service.

Although the Chair of the GB is the official representative of the IGS to external organizations, the CB, consonant with the directives established by the Governing Board, is responsible for the day-to-day liaison with such organizations.

Through the existing reciprocity agreement between IGS and IERS, the CB represents the IGS as the GNSS Technique Center for IERS; as such, its designated representative (subject to Governing Board approval) is a voting member of the IERS Directing Board (together with the Analysis Center Coordinator or designee). This representative is to be selected from the membership of the IGS Governing Board. In turn, the IERS Directing Board designates a representative to the IGS Governing Board. This arrangement is to assure full cooperation between the two services.

The long term functioning of IGS is assured through redundancy of most of its components, though this does not apply to the CB. For this reason the performance of the Central Bureau is to be formally reviewed by the GB at least every five years. On these occasions the CB will either reconfirm its commitment to the IGS for the next period of five years or announce that it will terminate operations after a transition phase of at least one year. The GB will formally approve the CB’s proposal, or, alternatively issue a Call-for-Proposal for a new IGS CB to take over responsibilities after the transition phase.

In summary, the CB performs primarily a long-term coordination role to ensure that IGS participants contribute to the Service in a consistent and continuous manner and adhere to IGS standards.


The IGS Infrastructure Committee (IC) is a permanent body established to ensure that the data requirements for the highest quality GNSS products are fully satisfied while also anticipating future needs and evolving circumstances. Its principal objective is to assure that the IGS infrastructure components that collect and distribute the IGS tracking data and information are sustained to meet the needs of principal users, in particular the IGS Analysis Centers, core Product Coordinators, Pilot Projects, and Working Groups. The IC reports directly to the GB. The Chair of the IC is a non-voting member of the GB.


The principal roles of the Governing Board (GB) are to set policy and to exercise broad oversight of all IGS functions and components. It also controls general activities of the Service, including restructuring, as appropriate to maintain efficiency and reliability, while taking full advantage of the advances in technology and theory. The GB membership should be balanced with regard to supporting organizations, as well as geographically.

The GB consists of up to twenty-one voting members and a number of non-voting members. They are distributed as follows:





Nominated by/Elected by

Chair and Vice Chair



4 yr.

yes     (in case of tie)

Must be current GB member/Governing Board

Vice Chairman


2 yr.


Central Bureau/Governing Board

Associates representatives

Analysis Center representatives


4 yr.


Nominating Committee/IGS Associates

Data Center representative


4 yr.


Network representatives


4 yr.


Appointed members      

Central Bureau/Governing Board

Representatives of Analysis, Data Centers or Networks


2 yr.


Members at large (up to)


2 yr.


Ex Officio Members

Director of the Central Bureau




Approved by Governing Board

Analysis Center Coordinator




Reference Frame Coordinator




Real-Time Analysis Coordinator




Timing Coordinator




IERS and IAG representatives

Representative of the IERS




Approved by Governing Board

IAG representatives




Non-voting members

Working Group/Project Chairs, Infrastructure Committee Chair, Network Coordinator, Secretariat




Approved by Governing Board

BIPM/CCTF representative




Chairman: The Chairman is one of the members of the GB elected by the Board for a term of four years with the possibility of re-election for one additional term. The Chairman does not vote, except in case of a tie. He/she is the official representative of IGS to external organizations. The immediate past Chairperson, if no longer a voting member of the Board, will be invited to continue as a non-voting member of the GB for a period of one year after completion of the term(s) as Chair.

Vice Chairman: The Vice Chairman may be appointed to assist the Chairman in carrying out his or her responsibilities, including standing-in as Chairman when needed. This position is nominated by the CB and does not need to be an existing GB member. The Vice Chairman is appointed by the GB.

Associates Representatives: For the Associates Representatives, which represent components of the IGS that are elected by the IGS Associate Members, a Nominating Committee conducts the elections. The Nominating Committee consists of three members, the chair of which is appointed by the Chairman of the GB and who is a member of the GB holding a position not currently up for re-election. For elections, the Nominating Committee presents to the Associate Members a list of at least two candidates for each position to be filled. The election will be determined by the number of votes received from the Associate Members. In the case of a tie, the election is by the members of the GB.

Appointed Members: There are an additional up to five voting members who are nominated by the Central Bureau and appointed by the Governing Board to two year terms. These include up to two members who represent the IGS Analysis Centers, Data Centers or Networks, and up to three additional members at large.

Ex Officio Members: By virtue of their positions within IGS, the IGS product coordinators and the director of the Central Bureau are considered ex officio members of the Governing Board with full voting rights. The Ex Officio members are approved by the GB every 4 years.

IERS and IAG Representatives: To assure coordination between the services, the IGS and IERS shares reciprocal board positions: the IERS nominates a representative to the IGS GB to be approved by the IGS GB. In turn, the IGS GB nominates two IGS representatives (voting) to the IERS Directing Board to be approved by the IERS DB. The Analysis Center Coordinator and the ICB Director (or designees) fulfill this duty for IGS. Similarly, to assure alignment between IAG and IGS, two ex officio board seats are open, subject to Governing Board approval, to the IAG President and an additional IAG representative designated by the IAG Bureau.

Non-Voting Members: The Network Coordinator, the Chairperson of the Infrastructure Committee, Working Group and Pilot Project Chairpersons and the Governing Board Secretariat are Governing Board members with voice but without vote. A representative of the BIPM, appointed by the BIPM/CCTF[iv] with agreement of the IGS GB, is a non-voting member of the GB. In turn, the IGS appoints a representative point of contact to the BIPM/CCTF.

Except for the Vice Chair who may be strategically selected from any organization, the elected and appointed members must be from different organizations. The ex officio members are not subject to such restrictions. All elected persons have staggered four-year terms, which are renewable once. All ex officio positions shall be confirmed by the Governing Board and reviewed every four years. Appointed members will have two year terms, which may be renewed without limit. The Governing Board membership should remain balanced with regard to supporting organizations, as well as geographically.

In case of a resignation from the Board, after consulting with the appropriate IGS components, the CB will nominate replacement candidates for election by the GB. The replacement will serve until the end of the term of the resigned Board member.

Members of the GB are eligible to be considered for IAG Fellowship with the appropriate rights and privileges after an initial two-year period.

Most GB decisions are to be made by consensus or by a simple majority vote of the members present, provided that there is a quorum consisting of a simple majority of voting members of the GB. In case of lack of a quorum the voting may be by mail. Voting by e-mail, fax, or mail on any issue is permitted by these Terms of Reference, and the number of mail or e-mail responses must be sufficient to constitute a quorum. Changes in Terms of Reference can be made by a 2/3 majority of all voting members of the GB. At any time the GB can ask for the resignation of the Chair, or any member of the Board, if a majority vote of all voting members of the GB so requests.

The Board shall meet at least annually and at such other times as shall be considered appropriate by the Chairperson or at the request of five members. The CB provides the secretariat of the GB.

For the GB to effectively assess the value of IGS Services to the user communities, and to ensure that the service remains up to date and responsive to changing user needs, the GB will organize reviews of the IGS components at appropriate intervals. The GB will select, on an annual basis, those groups (Analysis Centers, Data Centers, Network Stations, and the Central Bureau) that are to be reviewed and from time to time may select other activities for review as it deems appropriate.

Strategic planning and implementation is a major and continuous task of the GB. A four-year Strategic Plan shall be developed, approved and published by the GB. Annual Implementation Plans shall be drawn up and presented for approval by the GB at its last meeting prior to the year concerned.


The Executive Committee (EC) of the IGS Governing Board is established as a committee that has specific responsibilities allowing it to act on behalf of the GB for the following purposes: 1) to formulate and organize issues that are to be brought to the GB for action, 2) to act for the GB when a quorum of the Board is not present, 3) to act for the GB when a full Board meeting is not possible or necessary. The EC is responsible for exercising the powers of the GB in the management of the business and affairs only to the extent set forth in these Terms of Reference. Any actions are communicated to the GB as soon as possible and reported and validated at the next Board meeting. The EC shall consist of six voting members, and one non-voting member of the GB:

  • Chair of the GB (voting)

  • Vice-Chair of the GB (voting)

  • Immediate Past Chair (non-voting)

  • Director of the CB (voting) and

  • Three additional voting members of the GB proposed by the Chair of the GB and approved annually by the GB.

Except for the power to amend these Terms of Reference, the EC shall have all of the powers and authority of the Board in the intervals between meetings of the GB, and subject to the direction and control of the GB. Three votes of EC members are needed for any decision. EC meetings are open to any GB member.


Associate Members are persons representing organizations that participate in any of the IGS components. The membership is balanced with respect to IGS components, organizational representation and geography, and is meant to represent institutions which contribute significantly to the IGS on a continuous basis. There shall be a maximum of ten Associates from any single organization. Members of the Central Bureau shall be counted separately from those of their parent organization.

The list of IGS Associate members is maintained by the IGS Associates Committee. The document “Charter of IGS Associates Committee" is a policy statement of the GB and is available from the CB and the IGS website (

Associate Members elect the six members of the GB representing Analysis Centers, Data Centers and Networks (except for those nominated by the CB). The list of Associate Members eligible to vote in elections must be approved by the GB prior to the election process. Current and former GB members are considered Associate Members.


IGS Workshops provide a forum for presentation and discussion of all aspects of IGS activities (strategy, analysis, network, data centers, current and future projects, working groups, products, user applications, and others). Workshops are to be held at least every two years, and are open to all interested persons. A Scientific Organizing Committee appointed by the GB shall be responsible for the organization of the technical sessions and shall ensure, in collaboration with the CB, that the workshop is appropriately documented through online proceedings and a “Recommendations” document. The GB shall approve the Recommendations document, which will be made available to the community via the IGS website (

The GB may organize ad hoc workshops or meetings as necessary, including “mini-workshops”, with a more limited scope and duration. These will focus on a few topics considered to merit particular attention and may be used as the mechanism for reviews of specific IGS elements, as mentioned above.


“Correspondents” are persons on a mailing list maintained by the CB, who do not actively participate in the IGS but express interest in receiving IGS publications, wish to participate in workshops or scientific meetings organized by the IGS, or generally are interested in IGS activities. Ex officio IGS Correspondents are the following persons:

  • IAG President and Vice-President

  • IAG Secretary General

  • President of IAG Commission 1: Reference Frames

  • President of IAG Commission 2: Gravity Field

  • President of IAG Commission 3: Earth Rotation and Geodynamics

  • President of IAG Commission 4: Positioning and Applications

  • Chairs and Directors of affiliated IAG Services

  • International VLBI Service for Geodesy and Astrometry (IVS)

  • International Laser Ranging Service (ILRS)

  • International Earth Rotation and Reference Systems Service (IERS)

  • International Doris Service (IDS), etc.

  • Chair of the Global Geodetic Observing System (GGOS)

  • IUGG Secretary General

  • Former Governing Board Members

The rules contained in the current edition of ‘Robert’s Rules of Order Newly Revised’ shall govern the IGS in cases to which they are applicable and in which they are not inconsistent with these Terms of Reference and any special rules that the IGS GB may adopt.


[i] The 2010 update includes inter alia the mission statement and goals and objectives from the IGS Strategic Plan 2008-2012 (see the IGS website under “Resources -> Knowledge Base”); sections on the newly established Infrastructure Committee and on IGS Workshops; new versions of the Charters on Analysis Centers, Data Centers and the Policy for Establishment of IGS Working Groups, Pilot Projects and New Operational Products; and a new Charter of the IGS Associates Committee.

[ii] The 2014 update adds a provision for a Governing Board “Chairman-Elect,“ elevates the Real-time Analysis Coordinator to a voting member of the Governing Board.

[iii] The 2017 update removes the Chairman-Elect position and replaces it with a the Vice Chairman position that more appropriately satisfies the need for continuity in IGS leadership. Terms of the appointed members are clarified to be two years, renewable indefinitely.

[iv] Comité Consultatif du Temps et des Fréquences (Consultative Committee for Time and Frequency), a committee of the Bureau International des Poids et Mesures (International Bureau of Weights and Measures), see