Practical
work of the study group (1999-2001):
a.
New members
Since
its creation in 1999 two new members joined SSG 4.188:
Spiros
Pagiatakis (Canada) joined as a full member;
Michael
Kuhn (Germany) joined as a corresponding member.
b.
Website of SSG 4.188
The
study group has its own website with the following URL:
http://research.kms.dk/~ssg4188/study_group/index.html
c.
SSG 4.188 in 1999-2001
The
work of the study group as a team suffers from problems that are not
uncommon to other study groups. The geographical spread of the members
as well as the spread research-wise makes it difficult to collaborate
closely on a daily basis. However, such collaboration exists on
individual basis between different members of the study group. Also,
for all members, it is useful to know about others with similar
research interests.
Right
from the start we knew that it would be difficult to arrange a meeting
for all members of the study group. Not all of us attend necessarily
the same conferences, and it would be unfair to arrange a meeting for
only part of the study group. Thus, in order to provide means of
communication between the members, the idea was to establish and to
use the official website of SSG 4.188. Initially we thought that such
website could be used for discussions and for exchange of ideas.
Regrettably, the website came up only few months ago, and at the
present the need for discussions seems to be rather limited. However,
this can change in the future and we keep this option open in case
somebody takes the initiative. The situation described above is
probably very typical and reflects the working conditions of many
special study groups. Firstly, it is difficult to share the ideas
prior to publishing. Secondly, it takes time to get involved in
discussions.
Fortunately,
in recent years it became more common for various research groups to
promote their work via the Internet. This is also the case for some
members of the study group. It is here that we see a realistic
possibility in the future of extending the website of SSG 4.188 and to
get a realistic picture of the research covered by the study group.
All it takes is to provide links from the website of SSG 4.188 to the
member’s URL and, possibly, to other related sites. Such procedure
will not involve the members with unnecessary additional work, and
seem to be a good way of utilizing the Internet without going into
trouble of writing special reports.
Scientific results in brief
The
website of SSG 4.188 contains a list of relevant recent publications
(not necessarily exclusively by the members of the study group)
published in 1999-2001 in Journal of Geodesy, Geophysics, Journal of
Geophysical Research (volume B), Geophysical Research Letters,
Geophysical Journal International, Pure and Applied Geophysics,
Physics and Chemistry of the Earth, Tectonophysics and others.
Furthermore, this list of publications includes references to relevant
presentations and papers at three major conferences: IAG International
Symposium on Gravity, Geoid and Geodynamics in Banff in 2000; 70th
Annual Meeting of SEG in Calgary 2000, and the 26th General Assembly
of EGS in Nice 2001.
The
overall impression is, that mass density directly/indirectly still
plays an important role in Geodesy, Solid Earth’s Geophysics and
Geology. The research activity seems to be spread over the whole
spectrum of topics ranging from e.g. the studies of the mathematical
structure of the ambiguity domain (i.e. the null-space of the inverse
gravimetric problem) to the practical modelling of the regional
geology in e.g. the Ukraine or in the United States. Even the old and
well-established concepts, e.g. such as the homogenous prism formula
for gravitational attraction or similar formulas for other elementary
bodies, is still the object of research. The goal is to modify the
formulas in order to increase the flexibility (i.e. to use them for
more complex mass density modelling) and to improve the speed of
computations.
In
Geophysics and Geology most of the papers involve mass density models,
which are fully 3D. In Geodesy the refinement of terrain corrections,
an important step in improving the geoid model, seem still to be a hot
topic. Furthermore, the goal of 1-cm geoid makes it worthwhile to
investigate the necessity of using more refined mass density models,
especially in mountainous areas. Not all countries are like e.g.
Switzerland prepared to introduce the refined mass density models into
the construction of their national geoids, but more and more countries
consider the possibility. In most countries the geoid accuracy of 1-cm
is still not achievable. Therefore, the efforts should be concentrated
on improving the fundamental data (Digital Elevation Models, gravity
information, vertical datum problems) rather than on complicating the
geoid modelling by introducing refined mass density information.
However, the use of refined mass density models for geoid modelling is
without doubt on the agenda for future high accuracy geoids.
Also,
in recent years, the launching of CHAMP and the preparations for the
new gravity missions GRACE and GOCE boosted the interest not only in
gravity and mass density, but also as a mean of studying geophysical
phenomena related to e.g. climate changes and similar (oceanography,
polar ice melting, postglacial rebound). The expected high accuracy of
the new gravity missions seems to make studies of these time-varying
phenomena a realistic possibility.
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