Jean O. Dickey
Jet Propulsion Laboratory, California Institute of Technology Pasadena, Ca 91109 USA

February 9, 2000

According to Webster, geodesy is a "branch of applied mathematics concerned with the determination of the size and shape of the Earth and the exact position of points on its surface and with a description of variations of its gravity field" (see other positions papers, i.e. Kouba et al. and Rummel for description of Geodesy's rich history and developments). Geodesy today is much more than this! The sphere of influence of space geodesy is ever enlarging, with impressive achievements in the last few decades in many diverse areas (such as geodynamics, planetary and atmospheric sciences, oceanography, tectonics, and ice studies). Examples include positioning at the millimeter level, enabling determination of crustal deformation and strain with unprecedented accuracy at high time resolution; water vapor monitoring via GPS; and improved gravity modeling and orbit determination, permitting an unparalleled view of the 1997-1998 ENSO event. The next millennium holds even more promise, with many planned developments, such as GOCE, GRACE, and ICESAT missions, densification of GPS networks, and the development of new technologies.

Geodesy requires a broad spectrum of synergistic activities, including theory, science, engineering, technology development, observations, analysis and the development of services. It is much more than applied math or an observation system. In addition to these components, an international association promotes publications, scientific conferences and schools, links to other societies and is a facilitator in the extension of geodesy to all geographical areas. Here, we propose a new structure for the IAG (Section 2). Reflection on the IAG's role in Global Change research is presented in Section 3.

The proposed IAG Bureau would consist of the President, Vice-President(s) and Secretary General and would provide an active IAG leadership taking full advantage of the power of the Internet and coming technology innovations. Members would be on the forefront of the new geodetic developments and at the same time have the experience needed for these positions.

The Executive Committee would consist of representatives of the Bureau and three branches: Sections, Services, and Communication / Outreach Branches (see Fig. 1). The benefits would be many. Each branch would have members on the Executive Committee, thereby having a direct representation, voice and vote in the IAG. In particular, the IAG Services would have greater status in the IAG structure, as is well deserved. Also, the development of the Communication / Outreach Branch would add more emphasis on these needed activities. Note that lines of communication are shown in Fig. 1 with links between all boxes rather than just the downward pointing lines of traditional organizational charts. Each of these branches is described in following sections.

Fig 1 Under construction85 The Bureau (a square) with three circles representing the three branches (Sections, Service, & Communication / Outreach) w/ lines connecting all structures.

2.2 The Sections Branch
This branch would be similar to the current IAG sections; however, we propose some reorganization of topics to better reflect current geodetic activities. Note that the space techniques would be part of each section. The current regular and special commissions (C's & SP's) would be reviewed with a goal of a revised C's & SP's structure that would better serve the IAG community. Special Study Groups would continue under the sections as before; however, they would be cross linked to services if appropriate (e.g. IAG/IAPSO Joint Working Group, Geodetic Effects of Non-tidal Ocean Processes, linked with the IERS Special Bureau on Oceans).

Section 1: Positioning and Crustal Deformation
Crustal Deformation

Section 2: Emerging Technology and Missions (ET & M)
New techniques and their evaluation
International coordination of ET & M, when appropriate

Section 3: Gravity
Terrestrial gravity measurements, networks and control stations
Determination of gravity field and geoid from terrestrial & space-based measurements
Reduction and estimation of gravity quantities

Section 4: Theory and Methods
Mathematical Geodesy (MG)
Links to other sections on the MG applications

Section 5: Global Geophysics and Interdisciplinary Studies
Global reference frames
Earth Orientation
Earth tides and time-variable gravity
Interdisciplinary Studies (e. g. mean sea level and post-glacial rebound)

Fig. 2 Section Branch Structure

The Service Branch would have three executive members (Fig. 2) representing the following:
Technique-oriented services: IGS, ILRS and IVS,
Time and Earth Orientation services; BIPM and IERS, and
Other Services: BGI, ICET, IGES, and PSML.

The services would be asked to keep close links to the sections and participate in Special Study Groups and Working Group as would benefit both branches.

This branch (Fig.3) would have two executive members. One member would represent the publications (Journal, Proceedings, Newsletters and websites) and would provide the IAG with a public information link. The second would take the lead on outreach, addressing schools and how IAG can affiliate the extension of geodesy to all geographic areas.

Fig. 3 Service Branch Structure

Fig.4 Communication / Outreach Structure


Several of the position papers address geodesy in light of global change and in particular with respect to the International Geosphere-Biosphere Program (IGBP). Recall that an IAG Ad Hoc Working Group on Global Change was created at the General Assembly in Vienna in 1991. The goals of the Working Group were twofold: (1) Determine if the IAG should be involved in the IGBP. Would the IGBP be more successful if the IAG were involved? If so, determine the role of the IAG. (2) In addition, the IAG should examine whether global change science and issues are being properly addressed within the IAG. The group did fulfill its objective and a full report (Dickey et al., 1993) was presented at IAG Executive meeting the following year (March 1992). The full report (16 pages) is being scanned and will be distributed electronically (hard copy will be available at IAG2000). Committee members and invitees are urge to review this document to benefit from the considerable effort made and the links began by this group.

The three main recommendations were:
1. The post of IAG liaison or representative to the IGBP should be established.
A new core program, "Global Sea Level and Ice Sheet System," should be established within the IAG taking the lead to address the issues of sea level and ice sheet volume changes, which are critical to the whole global change program.
A Special Study Group on Global Sea Level and Ice Sheet Systems should be formed within Section 5 to study these issues, address the formulation of such a IGBP core program and liaison with the other IUGG associations.

The need for precise reference systems was certainly a major consideration. Later after considerable discussions with IGBP leaders, it was realized that many of the goals with common to the IGBP Program LOICZ (Land Ocean Interaction in the Coastal Zone). Dialogue was begun with Bill Carter attending one of their meetings in the Philippines.

Acknowledgement: I would like to thank Richard Gross and Ruth Neilan for their interesting discussions.

Dickey, J.O, C.C. Boucher, B.C. Douglas, B.H. Hager, T.A. Herring, H.G. Kahle, J.B. Minster, W.R. Peltier and C.R. Wilson, The International Association of Geodesy's Role in Global Change Position Paper, 16 pp, presented at the IAG Executive Meeting, Ohio State University, March 1993.