September 1999 - April 2001


During this reporting period, the SSG organized its membership, created an internet web site, had one official meeting, and was represented at a number of conferences and workshops dedicated to vertical reference systems. The group is heavily interrelated with other structural entities of the International Association of Geodesy, including special study groups and commissions and special commissions of other sections. In fact many important works related to the theory of height systems have been accomplished by individuals outside the group.

Internet Web site:

This site includes several pages describing







These pages are largely self-explanatory, but it is noted that the page listing the members has several links to web pages maintained by regular and corresponding members who themselves are leading specific related areas of research or services. The bibliography is extensive, though not complete, and includes references to past works related to the theory of vertical datums and height systems. The web page for Reports includes circular letters and reports from the president of the group, as well as other relevant documents.

To provide further insight to the variety of vertical datums existing around the world, a questionnaire was distributed to national representatives of the IAG asking them to furnish information on their height system, including the availability GPS/leveling data. A compilation of this information will shortly also be accessible on the SSG web site.



On the occasion of the International Symposium on Gravity, Geoid and Geodynamics 2000, held in Banff, 31 July - 4 August 2000, the SSG met to introduce its activities and request improvements and other input from the geodetic community to make the group more productive and informative. Most of the suggestions concerned obtaining basic information such as definitions and data on height systems; these have been and are being incorporated in the web site, as exemplified by the compilation of vertical datums.

Other symposia and workshops of special interest to the SSG include the following and were (will be) attended by members of the SSG:

1. World Height System Workshop, Prague, 7-9 November, 2000; organized by the Geographic Service of the Czech Armed Forces. A partial set of contributions, titled “The way forward to come to an improved world height system,” may be obtained from Villiam Vatrt (e-mail: or Marie Vojtiskova (e-mail: The program is also available on the SSG web site.

2. IAG Symposium, Vertical Reference Systems, Cartagena, Columbia, 20-23 February 2001; organized by the Instituto Geográ fico Agustí n Codazzi. The proceedings of the symposium will be published in the Springer IAG Symposia series. The program of the symposium is also found on the SSG web site.

3. IAG Scientific Assembly, IAG-2001, Budapest, Hungary, 2-8 September 2001; organized by the IAG and the Hungarian Academy of Sciences. This Assembly features a session (A4) titled “Vertical Datums: Determination Techniques and Unification” and is chaired by the President of the SSG. The program will also be posted on the SSG web site and it is planned to produce a proceedings of the presented papers.



Besides the bibliography provided on the SSG web site, other extensive lists of relevant publications may be found in the links related to the activities of the European and South American Reference System projects.



While the work of the group has been rather inhomogeneous we have tried to provide at least a focus for activities via the internet site which is being updated periodically. Major projects in Europe and South America currently in progress to modernize the corresponding geodetic reference systems, including the vertical datums, have overshadowed work in this Study Group, and much activity is consequently seen in other relevant structures of the IAG. It is hoped that this SSG can, at least, provide a point of common interest.


Christopher Jekeli

President, SSG 4.191



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