Journal of Geodesy

lournal of Geodesy (1995) 70:127-130

© Springer-Verlag 1995

lAG Newsletter Ole Baltazar Andersen, Assistant Secretary General IAG Central Bureau, Department of Geophysics, Juliane Mariesvej 30, DK-2100 Copenhagen Oe, Denmark Fax: +45 35 82 25 65, E-mail: [email protected], URL:http://www.gfy.ku.dk/~iag/

The IAG Newsletter is under the editorial responsibility of the lAG Central Bureau. In each issue of Journal of Geodesy the newsletter includes the following topics: Infomaations. Reports of IAG symposia. Reports by National Correspondents. Reports from IAG Special Study Groups. Symposia announcements. Book reviews. Fast bibliography. An up-to-date information medium is one of the key elements. The IAG Newsletter, included as appendix of the Journal of Geodesy, should play this role, and therefore be considered as an open forum. Contributors are welcomed to send any information or document (preferably in electronic form) which may be of interest for this purpose. This should complement the informations already send by the IAG officials or the IAG symposia organizers (reports and announcements). Books to be reviewed are under the responsability of : Herman van Gysen Department of Surveying and Mapping University of Natal, King George V Avenue Durban 4001, South Africa, E-mail: [email protected] and Prof. Martin Vermeer, Finnish Geodetic Institute, ilmalankatu 1A, SF-00240 Helsinki, Finland, E-mail: [email protected]

Information In M e m o r i a m . Dr. Attallah M. Wassef died on October 19th 1995 in his 74th year. The IAG Central Bureau expresses its deepest sympathy to his family and colleagues. His orbituary will be published in a future Newsletter.

I A G new Information Service on World W i d e W e b . The lAG Central Bureau is presently setting up a home page on World Wide Web as an open and up-todate information medium. On this home page it is possible to access information for general use relevant to the IAG community. Structure of the IUGG and IAG IAG address list Educational centers Information about the Special Study Groups lAG and IUGG resolutions in English and French Links to other World Wide Web servers related to Geodesy. Much more ........... The IAG home page can be accessed by using any World Wide Web browser like Mosaic, Netscape or Cello at the following address: URL: http://www.gfy.ku.dk/Mag/ As we are keen on improving the services provided on the lAG home page please provide corrections, updates, suggestions and proposals to the Central Bureau by email to [email protected]

128 Below is shown the IAG home page as per October 28th. 1995.

this school which is therefore intended to provide the basic mathematical theory of boundary value problems and, on the same time, their application to many different items, in geodesy, having the knowledge of the geoid as common point. As we know, on the same subject, there are a number of different approaches, based on different kinds of deterministic or stochastic approximation theories; yet these items are so important that they will deserve a school on their own; so we stress again that this school is concentrated on the B.V.P. approach arriving at all its practical applications. The program of the lectures is divided in the following parts: MATHEMATICAL FOUNDATIONS Potential theory E. Martensen - S. Ritter (Mathematical Inst., Univ. Karlsruhe): Harmonic functions - basic properties; mean values, Harnack theorem; Gauss-Green theorems fundamental solutions; regularity at the boundary of a harmonic function; measures and layers; numerical solution of BVP's by integral equations; boundary elements.

Symposia announcements International Summer School of Theoretical Geodesy. "BOUNDARY VALUE PROBLEMS AND THE MODELING OF THE EARTH'S GRAVITY FIELD iN VIEW OF THE ONE CENTIMETER GEOID" (Como, May 26 - June 7, 1996) Sponsored by the International Association of Geodesy 1st Circular letter This is the 3rd Course of a series devoted to form young scientists in specific fields of Geodesy. Thereby it is tried to give a complete picture of their conceptual basis as well as of their implementation and applications to the chosen subject. This time the particular object of our interest is the determination of the geoid with very high accuracy, namely the 1 cm level, which is possible today, or it will soon be. There is little doubt that the determination of the geoid has become in recent years a very popular item, because of its practical importance in connecting orthometric to ellipsoidal heights; yet the determination of the geoid has a very deep theoretical root in the formulation, the analysis and the solution of boundary value problems. This is in fact the particular road followed by

Free BVP's analysis and their numerical solution M. Biroli (Mathematical Dept., Politecnico Milano): Free BVP's in mathematical physics (examples); formulation by variational inequalities, regularity of the solution; formulation by Legendre transforms or partial Legendre transforms; control-theoretical approaches. Random harmonic fields Y. Rozanov (Steklov Mathematical Inst., Moscow): Basic definitions and properties of generalized stochastic processes; harmonic random fields (stochastic Green's identities); regularity and trace theorems; stochastic BVP's. BASIC GEODETIC THEORY The hierarchy of geodetic BVP F. Sanso' (D.I.I.A.R., Politecnico di Milano): Data and formulation of BVP's; the main BVP's of interest in Geodesy; vector/scalar Molodensky - Stokes fixed-boundary gravimetric altimetry/gavimetry problems; conditions for existence uniqueness and regularity of the solutions; overdetermined BVP's. -

Formulation and linearization of BVP: from observables to a mathematical model. B. Heck (Geodetic Inst., Univ. Karlsruhe): Linearization and various approximations of geodetic BVP's; conditions of validity of the approximations.

129 Classical solutions of GBVP and their implementation. H. Suenkel (Dept. Mathematical Geodesy, Tech. Univ. Graz): Classical numerical methods for the solution of geodetic BVP's; Stokes integral on the sphere and its Fourier approximation; ellipsoidal corrections; Molodensky's series. APPLICATIONS Topographic effects in gravity field modeling for BVP. C.C. Tscherning (Geophysical Dept., Univ. Copenhagen): Topographic effects for the manipulation of geodetic BVP's; potential and various functionals of elementary mass elements (prisms, cylindrical sectors, etc.); calculation strategies (exact formulas, approximate integrals, Fourier methods). Global models for the 1 cm geoid: present status and prospects R.H. Rapp (Dept. Geodetic Science, Ohio State Univ.): The new global model; the data; steps leading to computation of the solution; validation and tests of the new model. Spaceborne gradiometry; the BVP approach. R. Rummel (Inst. Astronomical and Physical Geodesy, Univ. Munich): The observables of spaceborne gradiometry and their transformation to complete or uncomplete BVP's; orthogonality rela-tions for scalar vector and tensor spherical harmonics; methods for non-diagonal boundary operators (least squares, biorthogonal sequences, etc.); noise propagation. Airborne gravimetry; the BVP approach. K.P. Schwarz (Dept. Geom. Engineering, Univ. Calgary): Observables in airborne gravimetry; the time filtering of the signal; the basic BVP for the vector g; numerical solutions and their stabilization by ground data. Does the 1 cm marine geoid exist? E.J.O. Schrama (Faculty of Geodesy, Tech. Univ. Delft): The geoid on the sea, the time variability problem; altimetry and geostrophic flow; marine gravimetry; computing the marine geoid. Beyond the main program a number of seminars, as traditional in our schools, are foreseen; they will be included in the final program. The venue of the school will be Villa Olmo - Como (Italy), which is also a traditional place for Geodesy because we had there the VIII Hotine Symposium in 1981. The period is May 26 - June 7, 1996.

As always the Lecture Notes will be published and distributed to participants; the cost will be included in the registration fee according to IAG bylaws. The registration fee is fixed in 500 USD.As organizers of the school we are also applying to get some support from international organizations in order to help those attendants who might need it: if you intend to ask for such a support please specify it immediately in answering to this first circular, since even in this case the requests will be taken into account in order of arrival. In case you intend to participate, reply as soon as possible, filling in the enclosed form: send us back the form not later then October 15(1995); you will receive the second Circular around Christmas. The accomodation and social program will be as usual organized by us and will be advertized in the 2nd Circular too. Yours sincerely, R. Rummel, F. Sans6

For any further information, please contact: Fernando Sanso' or Elena Raguzzoni, Dipartimento di lngegneria Idraulica, Ambientale e del Rilevamento, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano - Italy, Telefax: +39-2-23996530, E-mail: [email protected] or [email protected], Tel.: +39-2-2399.6504 or .6506

Forthcoming Symposia related to Geodesy 1996 January 19-22 International Conference on Disasters and Mitigation (INCODIM) Madras, India 1996 March 25-29 26th Intl. Syrup. On Remote sensing of Environment and 18th Annual Symp of the Canadian Remote sensing society, Vancouver, Canada. 1996 May 6-10 European Geophysical Society, XXI General Assembly, The Hague, Netherlands 1996 May 20-24 AGU spring Meeting Baltimore, Maryland, USA

130 1996 May 26-June 7 International Summer School of Theoretical Geodesy Como, Italy 1996 June 17-22 PACON 96. The seventh pacific congress on Marine science and technology, Honolulu, Hawaii 1996 June 25-28 Eighth FIG Inter. Symp. on Deformation Measurel~qents, HongKong, I996 July 1-4 Second International Conference GALOS Denpasar, Bali, Indonesia 1996 July 14-21 31 st COSPAR scientific Assembly B irmingham, United Kingdom. 1996 July 23-27 Western Pacific Geophysics Meeting Brisbane, Australia lAG Sponsored 1996 Sept. 7-16 XII International Course in Engineering Geodesy Graz, Austria 1996 Nov ? Joint Symposium of IGC and IgeC, Tokyo, Japan 1996 December 15-19 AGU Fall Meeting, San Francisco, California, USA

Reports of lAG symposia. Airborne Gravimetry Symposium, IUGG XXI General Assembly, Boulder, Colorado, July 13, 1995 The IAG Symposium G4 on 'Airborne Gravity Field Determination' was held during the XXI IUGG General Assembly in Boulder, Colorado, July 2-14, 1995. It was the first lAG Symposium dedicated to this topic, although previous symposia in Vienna (From Mars to Greenland), Graz (Gravity and Geoid), and Calgary (KIS 1994) had sessions devoted to airborne gravimetry, thus underlining the importance of this emerging field.

The papers were presented in three sessions, namely System Concepts and Critical Design Features, Modelling and Algorithms, Application Areas, System Tests, and Results. Each session was introduced by a review paper, addressing the scope of the session or presenting one major topic related to its theme. The contributions covered theoretical as well as practical aspects, and provided information on both the status of and emerging trends in airborne gravimetry. The current status is characterized by the fact that there are a number of operational scalar airborne gravimeter systems which achieve accuracies between 2 and 5 reGal (RMS) and wavelength resolutions between five and several hundred kilometres. Results achieved with these systems have shown their value in prospecting and in identifying regional tectonic structures. In geodetic work, they should be useful in supplying geoid undulations in areas without gravity coverage. On the other hand, there are a number of experimental systems of both scalar and vector type, which have the promise of reaching higher accuracy and resolution. Recent results indicate that a level of 1 regal (RMS) is achievable and that wavelength resolution to 2 or 3 km might be possible. The refinement of the dynamic error model, more sophisticated estimation procedures, downward continuation of gravity, and dedicated hardware developments are some of the emerging trends. Results of commercial and experimental systems strongly support the view that more attention has to be given to the influence of aircraft dynamics on sensor sensitivity. There is also a need to more clearly define which accuracy measures should be used to characterize a system. Simple accuracy figures, like the ones given above, tell only part of the sto W and should be replaced by an agreed-upon set of performance parameters. Comparative testing of different systems over a well-established test range might be a good way to come to grips with some of these problems. Since there is considerable room for further research in this area, the IAG has decided to continue SSG 3.164 which will establish a research program to address some of these problems. The proceedings of the symposium have been pubIished. They contain all but one of the papers presented. Thanks are due to the authors who arranged their busy schedules to comply with the strict publication deadlines, to John Brozena and Gunter Hein who, together with the undersigned, organized the symposium, and to Rene Forsberg who chaired the poster session. The proceedings can be ordered from: The Department of Geomatics Engineering The University of Calgary Calgary, Alberta Canada T2N 1N4 Fax: 001-403-284-1980 E-mail: [email protected]