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## Report Of IAG Section IV

**-GENERAL
THEORY AND METHODOLOGY-
**

**ON
THE ACTIVITIES BETWEEN 1999 AND 2001**

**Bernhard Heck, Section
President**

University of Karlsruhe

Geodetic Institute

Englerstrasse 7

D-76128 Karlsruhe

Germany

The structure of Section IV in the period 1999 - 2003 is essentially the
same as in the former four-year period. It consists of the Special
Commission

SC1 : Mathematical and
Physical Foundations of Geodesy

Chair: P.
Holota

covering broader and long-term items of geodetic theory and methodology
in its sub-commissions and working groups, and of the five Special
Study Groups

SSG 4.187 : Wavelets in
Geodesy and Geodynamics

Chair: W.
Keller

SSG 4.188: Mass Density
from Joint Inverse Gravity Modelling

Chair: G.
Strykowski

SSG 4.189: Dynamic Theories
of Deformation and Gravity Fields

Chair: D. Wolf

SSG 4.190:
Non-Probabilistic Assessment in Geodetic Data Analysis

Chair: H.
Kutterer

SSG 4.191: Theory of
Fundamental Height Systems

Chair: C.
Jekeli

This structure has been set up on the occasion of the IUGG General
Assembly in Birmingham 1999 in order to cover the most important
aspects of contemporary geodetic theory, and has proven to be highly
efficient in the first half of the working period.

Besides the thematical work done in the various bodies of Section IV -
which is reported below in detail - the planned changes of the IAG
structure have played a central role in the past bi-annual period. In
contrast to other IAG sections, the scope of Section IV is not
confined to a specific topic in Geodesy such as positioning, or
gravity field determination, or geodynamics; the accent here is rather
on the systematic (mathematical) treatment of groups of problems.
Therefore it is quite natural that most topics treated by the bodies
in Section IV are shared in one way or another with other IAG
sections, adding sometimes a different, more general point of view,
but without just duplicating the work. Ideally, the mathematical
problems occurring in the topic-oriented sections should be reflected
upon in Section IV and solved on a general basis. Another principal
scope of Section IV is to develop mathematical tools and to take up
available approaches already developed in other fields of Science and
to adept them to Geodetic Science; a prominent historical example is
Least Squares Collocation which was developed in the seventies mainly
in Section IV and nowadays is a basic tool in many branches of
Geodesy. In recent years, e.g. spatial statistics, robust statistical
methods, fuzzy theory and the use of wavelets have been thoroughly
investigated in Section IV for applications in Geodesy; some of these
approaches seem to be rather promising and to become highly efficient
tools in geodetic data analysis. Concerning the plans for a new IAG
structure it is scheduled to abolish the present sections and to
replace them by four topic-oriented commissions, dealing with

1) Geometric Reference
Frames

2) Gravity Field

3) Earth Rotation and
Geodynamics

4) Positioning and
Applications.

The task of these new commissions is to promote the advancement of
science, technology and international cooperation in their field.
Besides the services, the commissions will form the main components of
the new IAG structure.

In the new structure an entity like the present section IV is no more
foreseen and visible at the highest level of organization below the
EC, the level of the commissions and services. But this does not mean
at all that geodetic theory and methodology will not play a
fundamental role anymore. Since one of the major tasks of the new
commissions is the promotion of science, these bodies will be
responsible for the development of theory and modelling in their
respective fields, too. Of course, this procedure cannot include the
development of general, topic-independent approaches of data analysis
and mathematical-physical foundations, methodology and
"general" theory of Geodesy. After many discussions a
solution of this problem could be found, consisting of the creation of
an inter-commission committee on general theory and methodology,
reporting directly to the EC. It is expected that the existence of
such a committee will make sure that e.g. mathematically interested
geodesists and application-oriented mathematicians and physicists
furthermore will find a home and meeting-place within IAG. The
implementation of the new structure, to be approved during the IAG
Scientific Meeting in Budapest in September 2001, is still a heavy
task and a challenge for Section IV in the next two years.

In the past bi-annual period 1999 - 2001 Section IV contributed to
different scientific meetings such as

- Seventh International Winter Seminar in Sopron/Hungary, February 19-23, 2001,

- International Symposium on Vertical Reference Systems, Cartagena/Columbia, February 20-23, 2001,

- First International Symposium on Robust Statistics and Fuzzy Techniques in Geodesy and GIS, Zurich/Switzerland, March 12-16, 2001,

and

-EGS General Assembly, Nice/France, March 25-30, 2001.

A strong input from Section IV will also be given to the IAG Scientific
Meeting in Budapest/Hungary, September 2-8, 2001. Finally it is
planned to continue the series of Hotine-Marussi Symposia on
Mathematical Geodesy in 2002; traditionally Section IV has been
strongly involved in these symposia, organized in Italy.

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