The book contains the papers presented at the IAG Symposium on Vertical Reference Systems held in Cartagena, Colombia, in February 2001. It covers the status report of existing height reference systems and the latest steps towards the establishment of a unified vertical reference system. Classical and modern height determination techniques are included as well as the determination of height reference surfaces like sea level and geoid. Emphasis is also given to the variations of the reference systems with time, i.e., sea level changes and geodynamic deformations.

The Symposium on Vertical Reference Systems (VeReS) was initiated on the occasion of the XXII General Assembly of the International Union of Geodesy and Geophysics (IUGG), Birmingham 1999, by Professor Dr. Wolfgang Torge, Past President of the International Association of Geodesy (lAG) and representative of lAG to the Pan-American Institute of Geography and History (PAIGH). The idea was to organise another joint symposium of lAG and PAIGH like the previous one held during the XX IUGG General Assembly at Vienna, Austria, in 1991. Good reasons for such a joint symposium were the great success and the ongoing activities of the Project on the South American Geocentric Reference System (Sistema de Referencia Geocentrico para America del Sur, SIRGAS) being sponsored by lAG and PAIGH since 1993. The SIR GAS Project (Working Group I) had presented a continental South American reference frame of 58 stations during the lAG Scientific Assembly at Rio de Janeiro, in 1997. This reference frame was already adopted by several South American countries as the basis for their new national horizontal geodetic datums (SIRGAS Working Group II). To overcome the problems of the heterogeneous vertical (height) datums between the individual countries, SIRGAS had installed its Working Group III "Vertical Datum" in 1997. As the discussion on the unification of vertical reference systems is also going on in lAG and other bodies of science and practice, it was decided to dedicate the symposium to this topic.

Geodetic reference frames are the basis for The programme of the Symposium was divided three-dimensional, time dependent positioning according to the Sub-commissions, Projects in all global, regional and national networks, in and Study Groups of Commission 1 into eight cadastre, engineering, precise navigation, geo- general themes: information systems, geodynamics, sea level studies, and other geosciences. They are 1. Combination of space techniques necessary to consistently estimate unknown 2. Global reference frames and Earth rotation parameters using geodetic observations, e. g. , 3. Regional reference frames station coordinates, Earth orientation and 4. Interaction of terrestrial and celestial frames rotation parameters. Commission 1 “Reference 5. Vertical reference frames Frames” of the International Association of 6. Ionosphere modelling and analysis Geodesy (IAG) was established within the new 7. Satellite altimetry structure of IAG in 2003 with the mission to 8. Use of GNSS for reference frames study the fundamental scientific problems for the establishment of reference frames. One day of the Symposium was dedicated to a The principal objective of the scientific work joint meeting with the International Congress of the Commission is basic research on: of Federación Internationale des Géomètres - Definition, establishment, maintenance, and (FIG) and the INTERGEO congress of the improvement of geodetic reference frames. German Association of Surveying, Geo- - Advanced development of terrestrial and information and Land Management. The space observation techniques for this contributions presented at this meeting are purpose. integrated into these proceedings.

An exciting and heart-pounding look at one of Western Canada's most adventurous individuals, known as a pioneer pilot of the heli-ski industry and as the first mountain-rescue pilot in the Canadian National Parks system. Jim Davies is an icon of competence and courage as the first heli-skiing pilot in Canada. But it is his groundbreaking work as a helicopter rescue pilot for Parks Canada that made him a legend to all who worked with him. His stellar career as a pilot overshadowed his other talents as a ski racer and artist. Jim received several awards for his work in mountain rescue, including the Helicopter Association International - Pilot Safety Award of Excellence, the Alberta Achievement Award for excellence in helicopter flying, the Summit of Excellence Award at the Banff Film and Book Festival, and the Robert E. Trimble Memorial Award for "distinguished performance in helicopter mountain flying." He is now retired and living in Banff, pursuing his love of painting and photography.

This volume includes a selection of papers presented at the IAG international symposium "Gravity, Geoid and Height Systems 2012" (GGHS2012), which was organized by IAG Commission 2 “Gravity Field” with the assistance of the International Gravity Field Service (IGFS) and GGOS Theme 1 “Unified Global Height System”. The book summarizes the latest results on gravimetry and gravity networks, global gravity field modeling and applications, future gravity field missions. It provides a detailed compilation on advances in precise local and regional high-resolution geoid modeling, the establishment and unification of vertical reference systems, contributions to gravity field and mass transport modeling as well as articles on the gravity field of planetary bodies.

This book on reference systems is the first comprehensive review of the problem of celestial and terrestrial reference systems and frames. Over 20 years, the importance of this problem emerged slowly as the accuracy of new observational techniques improved. The topic has already been approached in several symposia such as Stresa (1967), Morioka (1971), Perth (1973), Columbus (1975, 1978 and 1985), Kiev (1977) and San Fernando (1978). Two IAU colloquia held in Turin (1974) and in Warsaw (1980) were exclusively devoted to discuss reference systems. During this time, the problem of terrestrial and celestial reference systems has been discussed also in many astronomical and geodetic symposia, but always among other topics. Thus, a review devoted solely to the definition and practical realization of such systems was needed. It is hoped that this book, containing modern comprehensive reviews of important facets of this problem will contribute not only to a better and wider understanding of the mathematics and the physics that are behind the concepts and the realizations, but also to future development in a field that can only expand with the rapidly increasing accuracy of geodetic and astronomical observations. We are pleased to thank all the authors of the book who have enthusiastically agreed to contribute to the book in their field of competence and have gracefully accepted guidance from the editors in the definition of the subject and of the interfaces with other chapters. We thank Prof. Y.

Introductory technical guidance for civil engineers and land surveyors interested in geodetic reference systems for land surveys. Here is what is discussed: 1. GEODETIC REFERENCE SYSTEMS 2. HORIZONTAL COORDINATE SYSTEMS 3. VERTICAL REFERENCE SYSTEMS.