New IAG Structure: Status September 2002

G. Beutler, on behalf of the

IAG Committee for the Realization of the New IAG Structure

Members of the

IAG Committee for the Realization of the New IAG Structure:

"Alan Dodson" <>

"Bernhard Heck" <>

"Klaus Peter Schwarz" <>

"C.K. Shum" <>

"Michael G. Sideris" <>

"Clark Wilson" <>

"C.C.Tscherning" <>

"Ruth E. Neilan" <>

"Manning John" <>

"Fernando Sanso" <>

  1. Introduction and Overview 1
  2. The New Structure in Overview 3
  3. Commission 1 (Task Leader: C.K. Shum) 4
  4. Commission 2: Gravity Field (Task leader: Michael G. Sideris) 5
  5. Commission 3 Earth Rotation and Geodynamics (Task Leader: Clark Wilson) 6
  6. Commission 4 Positioning and Applications (Task leader Alan Dodson) 7
  7. Intercommission Committee on Theory (Task leaders: Bernhard Heck and Peiliang Xu) 7
  8. Intercommission Committee on Geodetic Standards 8
  9. Outreach Branch 8
  10. IAG Project IGGOS (Integrated Global Geodetic Observing System) 9
  11. Summary and Action Items 10

  1. Introduction and Overview

The new IAG structure was developed after the IUGG General Assembly in Birmingham in summer 1999. Between summer 1999 and summer 2001 a thorough review of the IAG work and structure was performed by the so-called IAG Review Committee, the work of which is documented in (Beutler et al., 2001), a report presented at the IAG Scientific Assembly in Budapest in September 2001 in Budapest. At the same meeting, the proposed new structure was accepted by the IAG Executive Committee and later on by the IAG Council, which held an extraordinary meeting on September 8, 2001 in Budapest.

At the same meeting (Rummel et al., 2001) proposed to create the IGGOS, the Integrated Global Geodetic Observing System as IAG’s first project.

It is worthwhile to cite a few lines from the new IAG Satatutes and IAG By-Laws, which were accepted by the IAG Council at the September 8, 2001 meeting. According to these Statutes the Mission of the Association is defined as:

The MISSION of the Association is the advancement of geodesy, an earth science that includes the study of the planets and their satellites. The IAG implements its mission by advancing geodetic theory through research and teaching, by collecting, analyzing, and modeling observational data, by stimulating technological development and by providing a consistent representation of the figure, rotation, and gravity field of the earth and planets and their temporal variations.

The Association’s objestives are subsequently stated in the IAG Statutes. The future scientific work of the Association is further specified in the new IAG By-Laws:

The scientific work of the Association is performed within a component-structure consisting of Commissions, Services, the Communication and Outreach Branch, and IAG Projects, hereafter called the Association-components or components.

The new ByLaws allow it furthermore to establish Inter-Commission Committees, where the following rules shall be observed according to the IAG ByLaws:

Inter-commission Committees shall handle important and permanent tasks involving all commissions. Each Inter-commission Committee shall have a steering committee consisting of the following membership:

    1. President appointed by the IAG Executive Committee.
    2. Vice-president appointed by the IAG Executive Committee.
    3. One representative from each Commission

The terms of reference for each Inter-commission Committee shall be developed by a planning group appointed by the IAG Executive Committee. The Inter-commission Committees report to the IAG Executive Committee. The Inter-Commission Committee will be reviewed every eight years.

The following specific tasks were identified in Budapest to be achieved between the IAG Scientific Assembly 1999 and the IUGG General Assembly 2003 in Sapporo

The work of mapping the old structure into the new one, of creating the planning group for the ICC on Theory, and of issuing the call for the outreach branch was given to the IAG Committee for the realization of the new IAG structure. It was decided furthermore that the creation of a planning group for the IAG Project called IGGOS (Integrated Global Geodetic Observing System) should be left to the initiative of Reiner Rummel and Gerhard Beutler (see section 10 of this report).

The planning group for the Inter-commission Committee on Theory was set up early in 2002. The group members are:

The discussions within this group and of the group with a broader community were rather intense, but very interesting. A certain convergence was reached and summarized in an e-mail sent out by the Chairman on July 2, 2002. The outcome of the work is presented in section 7 of this report. It is in essence based on a summary by Bernhard Heck and the first report of the Planning Group comiled by Peiliang Xu.

The IAG Committee for the realization of the new IAG structure so far held three meeting (on September 6 2001 in Budapest, December 11, 2001 in San Fracisco, and on April 26, 2002 in Nice).

The five Section presidents agreed to serve as task leaders for the creation of the four new commissions and the intercommissio committee on theory. The outcome of their work will be summarized in sections 3-7. Christian Tscherning, IAG Secretary General, is the task leader for the establishment of the Communication and Outreach Branch.

At its meeting in Nice the Committee decided to support a proposal made by Proff. Erwin Groten (who was invited to attend the Nice meeting) and Erik Grafarend to create an Intercommission Committee on Geodetic Standards. It was furthermore decided that Section V should take the leadership in the planning group for this committee, and that the IAG services, in particular the IERS, IGS, IVS, ILRS, and the gravity-related services should be represented in the planning group. (The IAG EC actually asked Clark Wilson, president of Section V to chair this planning group and to create it with prominent representation from the services, in particular from the IERS, the IGS, IVS, ILRS, and the gravity-related services.)

  1. The New Structure in Overview

The services associated so far with the IAG were invited to become official IAG Services under the new structure. The following services made the decision to follow this invitation in the sense defined by the new IAG Statutes and By-Laws:

The IAG services work and act in a relatively independent way. Their decision to join the IAG as services in the sense of the new statutes and by-laws could not be „enforced" by the IAG. The Committee on the Realization of the New Structure is very much pleased by this positive response.

According to the IAG By-Laws the following four commissions shall be set up:

Commission 1 Reference Frames


    1. Establishment, maintenance, improvement of the geodetic reference frames.
    2. Advanced terrestrial and space observation technique development for the above purposes.
    3. International collaboration for the definition and deployment of networks of terrestrially-based space geodetic observatories.
    4. Theory and coordination of astrometric observation for reference frame purposes.
    5. Collaboration with space geodesy/reference frame related international services, agencies and organizations.

Commission 2 Gravity Field


    1. Terrestrial, marine, and airborne gravimetry.
    2. Satellite gravity field observations.
    3. Gravity field modeling.
    4. Time-variable gravity field.
    5. Geoid determination.
    6. Satellite orbit modeling and determination.

Commission 3 Earth Rotation and Geodynamics


    1. Earth Orientation (Earth rotation, polar motion, nutation and precession).
    2. Earth tides.
    3. Tectonics and Crustal Deformation.
    4. Sea surface topography and sea level changes.
    5. Planetary and lunar dynamics.
    6. Effects of the Earth's fluid layers (e.g., post glacial rebound, loading).

Commission 4 Positioning and Applications


    1. Terrestrial and satellite-based positioning systems development, including sensor and information fusion.
    2. Navigation and guidance of platforms.
    3. Interferometric laser and radar applications (e.g., Synthetic Aperture Radar).
    4. Applications of geodetic positioning using three dimensional geodetic networks (passive and active networks), including monitoring of deformations.
    5. Applications of geodesy to engineering.
    6. Atmospheric investigations using space geodetic techniques.

Each Commission shall have a Steering Committee, with a maximum of twelve voting members, which shall define the appropriate sub-structure of the Commission, which may consists of the following components:

    1. Sub-commissions,
    2. Study Groups.
    3. Commission Projects

A planning group for the IGGOS was set up, a first meeting was held in May 2002 in Washington. The current status will be summarized in section 10 of this report.

  1. Commission 1 (Task Leader: C.K. Shum)

This proposal emerged from discussions in Nice before, at the, and after the third meeting of the IAG Committee for the Realization of the New IAG Structure on April 26, 2002

The following Sub-commissions (SC) shall be set up:

SC1.1: Coordination of Space Techniques

Take over the coordinating role of its predecessor CSTG in a changed environment. The SC shall establish and further the contact of the space geodetic services based on space techniques, in particular IERS, IGS, ILRS, IVS and commission projects like DORIS.

SC1.2: Global Reference Frame

Address research-related and practical aspects of establishing the global reference frame. Address fundamental issues of the multi-technique global geodetic observatories. This SC must play a strong role in the new IAG project IGGOS. Its activities shall be coordinated with the IERS. SC1.3 shall in particular establish and maintain the contact with COSPAR.

SC1.3: Regional Reference Frames

SC1.3 shall offer a home for service-like regional reference frame activities AND address common aspects of these units. In order to avoid the creation of sub-sub-commissions , it is proposed to formally establish

with the understanding that these subcommissions also form the steering committee of SC3. Aspects of common interest shall be addressed, combined workshops, sessions at workshops, etc. shall be organized.

SC1.4: Satellite Dynamics

This SC shall address problems of satellite dynamics, which are outside the scope of the services. One might, e.g., think of the materialization of the celestial reference frame in satellite geodesy as a central theme, where aspects like the transfer of the Quasar-derived frame into the optical domain, but also the the value of modern high-accuracy astrometric places (based on modern telescopes, CCD-equipment) could be addressed.

The following three Commission Projects are proposed:

CP1.1: Altimetry: The project shall promote the free access to all satellite altimetry data and its use for geodetic reference frames, in particular height systems. It shall set up the basis for a unified multi-mission long-term record of altimeter data and investigate new techniques and aplication

areas of satellite altimetry (e.g., off-nadir altimetry, altimetry over land, laser altimetry etc.). The necessary steps towards the establishment of an altimetry service shall be studied.

CP1.2: GNSS: The main objective of this project is the coordination of geodetic activities with respect to the new global navigation satellite systems. The links to the international bodies involved in the establishment of new missions and systems shall be maintained and intensified. The adequate use of GNSS for geodetic applications shall be studied in cooperation with the subcommissions of Commission 1.

CP1.3: DORIS: The project shall coordinate the establishment of a DORIS service. In this task, it is cooperating closely with the other components of Commission 1 and the existing IAG services in this field (IERS, IGS, ILRS, IVS). The project will be discontinued as soon as a DORIS Service is installed.

  1. Commission 2: Gravity Field (Task leader: Michael G. Sideris)

The new Commission is derived mainly from the existing Section III (Determination of the Gravity Field), with elements of Sections II, IV and V. In fact mapping the old to the new structure, one can argue that the new Commission 2 should consist of all of existing Section III, Special Commission 7 (Satellite Gravity Field Missions) from Section II, Special Commission 1 (Physical Foundations of Geodesy) with Sub-commission 3 (Boundary Value Problems) from Section IV, and even part of Comission 5 (Earth Tides) from Section V. Of course the latter can fit as well under the new Commission 3 (Earth Rotation and Geodynamics).

Although the theoretical aspects of SC1 and its sub-commission 3 could be covered under the proposed Inter-commission Committee on Theory, it is felt that their natural place is under the new Commission 2, with full cooperation and coordination with the activities of the Inter-Commission Committee.

The five major thematic areas of the new Commission 2 will be:

Based on the above themes. there are probably only three major elements that will define the structure of Commission 2. In terms of Sub-commissions, these are:

The proposed SC2.3 might be part of SC2.1 or SC2.2 but, given the very high importance of the new satellite missions, it is felt that, at least initially, this should be a separate sub-commission to deal with the special issues and the variety of applications of these missions. Several study groups similar to the ones that exist currently would again be established to (i) investigate more specific topics and (ii) coordinate regional efforts of gravity mapping, geoid determination, vertical datums, etc.

Commission 2 has very strong links to the newly established International Gravity Field Service (IGFS). consisting of:

IGFS’s terms of reference are avilable under a separate document. It is clear that the givenning bodies of Commission 2 and IGFS should have a few common members on their Boards to ensure constant communication and proper coordination of their activities.

  1. Commission 3 Earth Rotation and Geodynamics (Task Leader: Clark Wilson)

As discussed at the IAG reorganization planning meeting on April 26, new Commission 3 Earth Rotation and Geodynamics, replaces Section V Geodynamics in the current structure. Activities not proposed to be included in the two subcommissions below are proposed to be assigned as follows:

Commission 3 is proposed to consist initially of two subcommissions:

SC3.1: Crustal Deformation

This proposed subcommission includes activities now under Commission XIV in the current IAG structure. The present Subcommission XIV contains sub-units related to particular geographical regions, including long-standing projects such as WEGENER, APSG, and the Central European Initiative, as well as Africa and Antarctica. The objectives of the current Commission XIV (described on its website are proposed to continue: First, to study 3-D motions, in active tectonic regions, post-glacial rebound and sea-level fluctuations and changes in relation to vertical tectonics along many parts of the coastlines and in relation to environmental fluctuations/changes affecting the geodetic observations; Second, to promote, develop and coordinate international programs related to observations, analysis and data interpretation for the three fields of investigation mentioned above; Third to promote the development of appropriate models.

SC3.2: Earth Orientation and Global Geophysical Fluids

This proposed subcommission includes activities within the IERS Global Geophysical Fluids Centers (GGFC). There are 7 special bureaus organized to examine the influence of the earth's mobile constituents (fluids) on the earth's orientation, defined broadly in terms of length of day, polar motion, nutations, geocenter and gravity. The 7 special bureaus are concerned with estimating influences of the core, mantle, oceans, terrestrial hydrology, atmosphere, and ocean tides. Activities under the present Special Commission 8 (Sea Level and Ice Sheets) are expected to be incorporated within the appropriate special bureaus. This proposed subcommission will follow the current goals of the GGFC (taken from the GGFC website to compute time variations of angular momenta and related torques, gravitational coefficients, and geocenter shift for all geophysical fluids based on global observational data, and/or products from state-of-the-art models, and to conduct scientific sessions at international meetings and conferences.

  1. Commission 4 Positioning and Applications (Task leader Alan Dodson)

The new Commission 4 will focus on multi-sensor applications, kinematic positioning, atmosphere propagation, monitoring of local geodynamic applications, etc.

The Commission shall have strong links to IAG-external organisations like FIG, ION, and (perhaps) to ISPRS. IAG-internally, the Commission must be linked to the IGS (implying an IGS representation on the Commission's steering committee).

Proposed Sub-commissions:

Two commission projects are proposed:

Open issues still are: the terrestrial systems, the height system.

  1. Intercommission Committee on Theory (Task leaders: Bernhard Heck and Peiliang Xu)

The proposed Terms of Reference for the Inter-commission Committee on Theory are:



Structure of the ICCT:

The working groups also might be called study groups.

  1. Intercommission Committee on Geodetic Standards

The planning group should be established as soon as possible.

  1. Outreach Branch

According to the minutes of the third meeting of the IAG Committee for the Realization of the new IAG structure the status is as follows: A Call for proposals for the IAG Outreach Branch was sent out on January 2, 2002. Only two proposals were received. For various, but different reasons both proposals did not seem suitable. Christian proposed that the search should continue. This view was shared by the Committee.



  1. IAG Project IGGOS (Integrated Global Geodetic Observing System)

The planning group for IGGOS is composed as follows:

The planning group is chaired by Gerhard Beutler till 2003, Hermann Drewes is the group’s secretary.

The planning group had a first meeting in Washington on May 27 in Washington. The meeting was intense and at times controversial. The establishmnent of IGGOS is far from trivial. A vision and a mission statement as well as objectives for IGGOS were subsequently developed by Gerhard Beutler, Jim Ray, John Manning, Hermann Drewes, and Reiner Rummel:




Two more documents were developed after this first meeting, one by Reiner Rummel and one by the Chairman:These two documents are attached to this e-mail as well (above mentioned documents (3) and (4)). Reiner tackled the problem from two points of view, namely the science point of view, where he advocates in essence few so-called IGGOS master products and asks for a strong IGGOS science plan, and the point of view of IGGOS relations to other observation systems (e.g., under UNESCO). I thought, on the other hand, that it would be useful to tackle the problem from the structural and organizational point of view. I am convinced that (a well defined set of) the existing IAG services must form the backbone of IGGOS.

IGGOS is seen as a unique opportunity for geodesy (and in particular IAG) to become a leader in interdisciplinarity in geophysics. First, the development of precise geodetic networks and the production of continuously-improving timeseries urge for a deep understanding of the interactions occurring in the Earth system that cannot be achieved by the geodetic community alone. Second, the global observation of the Earth system through its rotation and gravity field, geodesy has unique insight into the large-scale mass distribution and global or regional mass motion. Geodesists should thus work in interaction with the rest of the geophysical community in the development of global fluid modelling. IGGOS must be a motivating framework and flagship.

Comments concerning the four documents were received and implemented early in September. Comments by Veronique Dehant and Chopo Ma should be mentioned in particular.

Hermann organizes a 1.5 day workshop. The proposed coordinates on November 22-23 2002 in Munich (immediately following the IERS Workshop at DGFI in Munich). The tentative agenda will be sent out in September 2002.

  1. Summary and Action Items

Summary: The present document gives an overview of the status of the IAG Restructuring process. As one can see the process is complex and far from complete. As all (more or less) independent elements of the process are now contained in one document, it should be relatively easy to achieve a higher level of consistency and uniformity

It is assumed that the task leaders should now be in a position to remove inconsistencies and to come up with short descriptions describing the Sub-commissions, etc. they wish to create.

Specific concerns were brought forward by Bernhard Heck:

I personally to not agree with the concerns regarding commission 1, but a general consensus must be reached in this issue. The above concerns should be sorted out rapidly.

Thanks to the work of Bernhard Heck, Peiliang Xu, Véronique Dehant, and the entire ICCT planning committee we now have a concrete proposal concerning the objectives and the structure of the new Inter-commission committee on theory.

No progress was made up till now with the ICC on Geodetic Standards. We are not yet in a critical situation, but we should have concrete proposals by the end of the year. We should define a planning group working with the same dedication, as that of the ICCT.

The planning of the IGGOS project is in a critical phase. The above mentioned documents are currently under review by IGGOS the planning group. The crucial issue is (as it was for years) to come up with a concrete plan. The three documents (1) vision, mission, objectives, (2) Reiner’s ideas, after a review, (3) my attempt to identify concrete IGGOS elements will be combined into one document and serve as the basis for the second meeting of the planning group. After this second meeting we should know, wether the IGGOS or a pilot phase thereof can be launched in summer 2003.

Concrete Action Items: