INTERNATIONAL ASSOCIATION OF GEODESY - TRAVAUX TABLE OF CONTENTS Foreword O.B. Andersen p.IV SECTION I: POSITIONING Report by the President F.K. Brunner p.5 Commissions Comm. X : Global and Regional Geodetic Networks C. Boucher p.9 Special Commisions SC4: Applications of Geodesy to Engineering H. Kahmen p.14 Special Study Groups SSG 1.154: Quality Issues in Real time GPS Positioning C. Rizos p.17 SSG 1.155: Active GPS Networks H. Tsuji n.a SSG 1.156: Avanced GPS Analysis for Precise Positioning G. Blewitt n.a. SSG 1.157: GPS Ambiguity Resolution and Validation P.J. de Jonge p.39 SSG 1.158: GPS Antenna and Site Effects J. Johansson p.42 SSG 1.159: Ground-Based GPS Meteorology M. Bevis p.51 SECTION II: ADVANCED SPACE TECHNOLOGY Report by the President R. Rummel p.69 Secretaries: P. Willis Commissions Comm VIII: Int Coordination of Space Techniques for Geodesy and Geodynamics (CSTG) G. Beutler p.72 Special Commissions SC6: "Wegener Project" S. Zerbini p.77 SC7: Gravity Field Determination by Satellite K.-H. Ilk p.82 Gravity Gradiometry Special Study Groups SSG 2.160: SAR Interferometry Technology R. Klees p.89 SSG 2.161: Probing the Atmosphere by GPS C. Rocken p.112 SSG 2.162: Precise Orbits using Multiple Space Techniques Remko Scharroo n.a. Services IGS - International GPS Service for Geodynamics G. Beutler p.127 SECTION III: DETERMINATION OF THE GRAVITY FIELD Report by the President R. Forsberg p.140 Commissions Comm III: International Gravity Commission I. Marson p.144 Comm XII: International Geoid Commission H. Suenkel p.146 Services BGI - International Gravimetric Bureau G. Balmino p.151 IGeS - International Geoid Service F. Sanso p.157 Special Study Groups SSG3.163: Assessment and Refinement of Global Digital Terrain Models D. Arabelos p.160 SSG 3.164: Airborne Gravimetry Instrumentation and Methods M. Wei (Canada) p.169 SSG 3.165: Global Gravity Field Determination and Evaluation N. Pavlis p.182 SSG 3.166: Local Gravity Field Modelling and Interpretation T. Basic n.a. SSG 3.167: Regional Land and Marine Geoid Modelling I.Tziavos p.189 SSG 3.177: Synthetic modelling of the Earth's gravity field. W.Featherstone p.211 SSG 3.178: Artic Gravity Project Rene Forsberg p.222 SECTION IV: GENERAL THEORY AND METHODOLOGY Report by the president P. Holota p.226 Special Commisions SC1 Mathematical and Physical Foundations of Geodesy E.W. Grafarend p.235 Special Study groups SSG 4.168: Inversion of Satellite Altimetry P. Knudsen p.236 SSG 4.169: Wavelets in Geodesy B. Benciolini p.239 SSG 4.170: Integrated Inverse Gravity Modelling L. Ballani p.242 SSG 4.171: Dynamic Isostasy L.E. Sjoeberg n.a. SSG 4.176: Models of Temporal variations of the gravity field D.Wolf p.251 SECTION V: GEODYNAMICS Report by the president M.Feissel p.255 Commissions Comm V: Earth tides H.-G. Wenzel n.a. Comm VII: Recent Crustal Movements T. Tanaka p.259 Special Commissions SC3: Fundamental Constants E. Groten p.270 SC3: Ad Hoc Working Party on Refractive Indices of Light... J. M. Rueger p.282 SC8: Sea Level and Ice Sheet Variations Geoffrey Blewitt n.a. Special Study Groups SSG 5.172: Understanding Natural Hazards-The Geodetic Contribution. S. Okubo p.304 SSG 5.173: Interaction of the Atmosphere and Oceans with the Earths Rotational Dynamics C. Wilson p.307 SSG5.174: Geophysical Interpretation of Temporal Variations of the Geopotential A. Cazenave n.a. SSG5.175: Interannual Variations of the Vertical and Their Interpretation Z.X. Li p.314 Services ICET - International Center of Earth Tides B. Ducarme p.322 IERS - International Earth Rotation Service M. Feissel p.328 PSMSL - Permanent Service for Mean Sea Level Woodworth p.334 BIPM - Bureau International des Poids et Mesures, Time Section Gerard Petit p.339 IAU/IUGG WG on Non Rigid Earth Rotation T. Herring p.346 OUT OF SECTION Committees reporting to the Bureau Cassinis Commitee W. Torge p.350 Committee for Geodetic Aspects of the Law of the Sea (GALOS)P. Vanicek p.362 COSPAR/IAU/IAG WG on cartographic coordinates, and for elements of the planets and sattellites. M Bursa p.363 SCAR Scientific Committee on Antarctic Research. D. Manning p.364 WGAS - IAU working Group on Astronomical Standards E Groten p.373 ISO TC 211 J. Ihde p.374 IUGG Inter Association Committee for mathematical Geophysics. M. Vermeer p.376 IUSM- Interational Union for Surveys and Mapping I.I. Mueller p.377 SIRGAS H. Drewes p.381 PAIGH - Panamerican Insitute for Geography and History W.Torge p.384 IAG Schools F. Sanso p.386 IAG Internet Home Page O.B. Andersen p.393 Foreword Every four year the International Association of Geodesy (IAG) publishes its reports for the past four year period, called the ”Travaux de l’Association Internationale de Geodesie”. The “Travaux “ is published shortly after the General Assembly of the International association of Geodesy held as a part of the General Assembly of the International Union of Geodesy and Geophysics (IUGG) which took place in Birmingham, United Kingdom between the 19th and the 30th of July, 1999. The Travaux is the complete collection of all the reports of all the bodies constituting the Association. This version of the Travaux contains a total of 25 reports. Each of the 5 sections within the IAG reports on their commissions, services, special commissions, special study groups and working groups. Finally a number out of sections reports are found. It is an instantaneous picture of the work performed the last four years by a large number of individuals and groups through international corporation under the auspices of the International Association of Geodesy. The ”Travaux” is published in a short timetable after the General Assembly, so that scientific information can be disseminated rapidly throughout the geodetic community. I would like to thank all the contributors who did their best to provide their report at the Birmingham IUGG General Assembly (or shortly after). During the last four year period the IAG has established a homepage on the Internet (www.gfy.ku.dk/~iag) as an open up-to-date forum for communication. Through this electronic address, all members of the IAG are now able to have almost real time access to all information related to the IAG. An electronic version of the ”Travaux” can also be found here. Ole B. Andersen Report of International Association of Geodesy Section I POSITIONING President: Fritz K. Brunner Technische Universität Graz Engineering, Surveying and Metrology Steyrergasse 30 A-8010 Graz Austria 1. Preamble The Handbook of Geodesy (1996) describes the tasks of Section I as: Section I is concerned with the scientific aspects of the measurement and analysis of regional and global geodetic networks as well as satellite, inertial, kinematic and marine positioning. The practical results of this research work should be made available through recommendations to National Survey Organisations. Applications of geodesy in engineering is a recent new task of Section I. Tremendous advances of GPS surveying have occurred, especially in precision and applicability. However, there are some remaining issues of accuracy and reliability of GPS surveying (hardware and software) which need to be addressed carefully. Recently, GPS measurements have shown the potential to be used as remote sensing tool of atmospheric parameters. Two main driving forces of the developments by Section I can be recognised: GPS technology is changing the methods and practical tasks of positioning, and the engineering applications of geodesy are a growing field with an important geodetic kernel. 2. Structure of Section I In order to achieve the above described tasks, Section I consists of the Commission X “Global and Regional Geodetic Networks” (President: C. Boucher, France) and of the Special Commission 4 “Application of Geodesy to Engineering” (President: H. Kahmen, Austria). Both commissions have established several working groups and address the longer term interests of positioning on an international basis. For the period 1995 - 1999, Section I set up several Special Study Groups (SSG) to investigate rather limited but highly relevant research topics with the goal to solve the underlying problems. One of the main activity of a SSG is the international coordination of the ongoing research in its field. In 1995 the following special study groups were established: SSG 1.153: Precise Marine Positioning: Surface and Seafloor (D. Egge, Germany) SSG 1.154: Quality Issues in Real Time GPS Positioning (C. Rizos, Australia) SSG 1.155: Active GPS Networks (H. Tsuji, Japan) SSG 1.156: Advanced GPS Analysis for Precise Positioning (G. Blewitt, UK) SSG 1.157: GPS Ambiguity Resolution and Validation (P.J. de Jonge, Netherlands) SSG 1.158: GPS Antenna and Site Effects (J. Johansson, Sweden) SSG 1.159: Use of GPS Positioning for Atmospheric Monitoring (M. Bevis, USA) In 1997, the SSG 1.153 was discontinued by the IAG Executive due to lack of communication. Most SSG worked extremely well which can be seen from their reports. The Steering Committee of Section I comprises of the Section President (F.K. Brunner, Austria), the Section Secretary (Y. Bock, USA) and the President of Commission X (C. Boucher, France). Meetings of the Steering Committee were held at IAG Executive Committee Meetings and at major international symposia. The reports by Commission X, SC4 and SSGs groups are given in the following section. The complete report of SC4 is available from the web-side-version of the Travaux. 5 3. Meetings and Highlights There were many international meetings held on topics of positioning for which IAG functioned as a sponsor. However, in my opinion three meetings had a special mission: a) Section I organised the symposium on “Advances in Positioning and Reference Frames” as a part of the Scientific Meeting of IAG in Rio de Janeiro b) SC4 organised a Symposium on “Geodesy for Geotechnical and Structural Engineering” in Eisenstadt c) Section I organised the Symposium G1 ”Positioning” at the General Assembly of IUGG in Birmingham.