IAG Newsletter

Ole Baltazar Andersen

IAG Central Bureau, Department of Geophysics, Juliane Maries vej 30, DK-2100 Copenhagen Ø, Denmark

e-mail: iag@gfy.ku.dk; Fax: +45 3536 5357; URL:http://www.gfy.ku.dk/~iag/

The IAG Newsletter is under the editorial responsibility of the IAG Central Bureau. It is an open forum and contributors are welcome to send material (preferably in electronic form) to the IAG Central Bureau. These contributions should complement information sent by IAG officials or by IAG symposia organizers (reports and announcements).

Each IAG Newsletter includes several of the following topics:

I general information

II. reports of IAG symposia

III. reports by commissions, special commissions or study groups

IV. symposia announcements

V. book reviews

VI. fast bibliography

Books for review are the responsibility of:

Christian Tiberius

TU Delft, Faculty of CEG,

Dept. of Mathematical geodesy and positioning

P.O.Box 5030 - NL 2600 GA Delft - The Netherlands

Fax: (+31) 15 27 83 711

E-mail: c.c.j.m.tiberius@geo.tudelft.nl

In Memoriam

Thaddeus Vincenty, the architect of much of the theoretical underpinnings for the 1983 readjustment of the North American Horizontal Datum, died on March 6, 2002 at the age of 81. Because of the tumultuous circumstances of his early life his geodetic career did not begin until almost his fiftieth decade. But from the 1960's through the 1980's his flow of publications, noted for both originality and usefulness, stamped him as one of the most outstanding geodesists of that period.

Born in rural southern Poland in 1920, Vincenty's early schooling was marked by his propensity for foreign languages. He became fluent in German and he learned English through self-teaching manuals. His formal education was interrupted by World War II and was never renewed. He underwent many hardships during the war, eventually ending in a displaced persons camp in Germany where his language versatility proved useful. Through the help of American relatives he emigrated to the U. S. in 1947, and a few months afterwards enlisted in the U. S. Air Force. His first ten years there involved mainly administrative assignments.

In 1957 he met a fellow airman who performed land surveys for the Air Force. Vincenty became fascinated and applied for assignment to this specialty. He took numerous mail correspondence courses in astronomy, surveying and mathematics, and learned how to program computers. Within 5 years he had become sufficiently adept to publish his first paper. His uniformed service in the Air Force ended in 1967. But his geodetic work continued unbroken as he retained essentially the same duties as a civilian.

During his span at the Air Force his favorite setting for publication was Survey Review (SR) which featured over a dozen articles by him. Vincenty's first paper, mentioned above, appeared in SR 129, July 1963. It compared the angle and direction methods for performing triangulation adjustments and unequivocally advocated the former. The careful and thorough numerical evidence by which he reached this conclusion was an earmark of his subsequent work which was always noted by its emphasis on precise reasoning, unambiguity, and specific computational recipes for obtaining the desired result. A uniform thread through all his research was the emphasis on efficiency, in the sense of achieving the optimal balance between precision and economy.

His special interests were geometric geodesy and adjustment procedures, and his investigations in these fields illustrated his goal of efficiency. For example, he would weigh (in the context of the 1960's and 70's) the respective advantages of desk calculators vs electronic computers, the latter being more cumbersome to program and access with perhaps no decisive edge in accuracy. Examples: (1) resection of azimuths from flare observations (SR 132, 1964); (2) transformation between geographic coordinates on different datums (SR 137, 1965); (3) computing meridional arcs (SR 161, 1971); (4) three-point resection from plane and geographic coordinates (SR 168, 1973). In a similar vein he would compare iterative and closed methods, with the aim of discerning the most efficient technique. In the case of solving the direct and inverse problems on the ellipsoid he favored the iterative approach (SR 176, 1975) and maintained his position in a critique of a closed solution many years later (Surveying and Mapping, Sept. 1985). But he was not a proponent per se of either desk calculators or iterative methods; he chose whatever means proved most efficient. The formulas he developed for the transformation of geodetic data between ellipsoids demonstrated a non-iterative technique for electronic computing (J. Geophys. Res., May 15, 1966), and in SR 189 (1978, pp.291-3) he published an elegant set of closed equations for the intersection problem on the ellipsoid. He himself became an expert programmer.

During the 1970's Vincenty undertook an exhaustive study of trilateration adjustment culminating in his article in SR 193 (1979) yielding comparative accuracies for a variety of choices for handling the data. It is probably the final word on the utilization of electronic distance measurements. A useful byproduct was an unprecedented accuracy of 1 part in 5 million gained in a trilateration adjustment at the McDonald Observatory in Texas, needed for its lunar ranging observations (SR 189, 1978, pp.295-302).

In early 1976 the National Geodetic Survey (NGS) recruited Vincenty by offering him a key role in its planned readjustment of the 1927 North American Horizontal Datum (NAD 27). After almost 30 years of uniformed and civilian service with the U. S. Air Force, Vincenty uprooted his family from Cheyenne, Wyoming, and moved to Washington Grove, Maryland, in the suburbs of Washington, D. C., where he remained for the rest of his life.

NAD 27, the official basis for horizontal positioning in North America for the past fifty years, needed replacement. NGS recognized that a critical component of the new adjustment would be the formulation of a mathematical model to meet current requirements for accuracy and adaptability. In NOAA Professional Paper NOS 2 "North American Datum of 1983", the official report of the project, it is stated " The mathematical model for the NAD readjustment was the height-controlled three-dimensional system. This formulation ... is conceptually simpler than the classical model for observation equations on the ellipsoid and is therefore easier to program for computers. Most important, it facilitates the combination of terrestrial data with space systems data (such as Doppler positions and VLBI position differences) in a straightforward way." Vincenty developed, implemented, and conceived essential features of that model.

The height-controlled three-dimensional system provided more computational flexibility than the conventional two-dimensional ellipsoidal configuration. Since this was to be an adjustment of a horizontal network, the height component was not adjusted. However, Vincenty realized that all components of space observables, like VLBI, would affect the desired solution. His most original concept was that of a "dual height" system in which the original height of a network station remained fixed, but, if three-dimensional observations were available at that point, all components of the latter (including the height component) would be utilized in adjusting the terrestrial coordinates. He later claimed (Surveying and Mapping, 1989) that "there are few problems...easier to grasp than this one". Nevertheless, the implementation involved many non-trivial details which were spelled out in a series of NGS Technical Memoranda and journal articles (e. g., Bulletin G‚od‚sique, 1980, pp. 37-43).

Vincenty's contribution to the final result, known as

NAD 83, was crucial. He was recognized by being presented the NOAA Meritorious Service Award in 1982. The official report of the project dedicated NAD 83 to William Bowie, who was responsible for NAD 27. Of course, Bowie, who had been long deceased and profusely honored otherwise, had nothing to do with NAD 83. My personal opinion is that it might have been more appropriate to dedicate it to Vincenty who had already retired by the time the report was issued in 1990.

After a ten year stint with NGS Vincenty retired in 1986. He continued his geodetic interests, publishing a number of articles in Surveying and Mapping on a variety of topics, still emphasizing his interests in geometric geodesy and adjustment theory. His last geodetic article, an exposition of the dual height system, appeared in 1989.

Vincenty was highly respected by all his associates in the Air Force and NGS. But, although he maintained many outside contacts, principally with B. R. Bowring with whom he collaborated on several papers, he was not as well-known in the general geodetic community as he should have been. Partly this was because he had little interest in the political aspects of geodetic associations and partly because a circulatory ailment hampered his mobility, thus restricting travel to meetings. He was invariably the first one to arrive at NGS in the morning, enabling him to obtain a head start on his tasks, but also securing the closest possible parking space for his car, thereby minimizing the distance to traverse to his desk. His co-workers remember him especially for his penchant for acronyms, for example, the computer program HOACOS (Horizontal Adjustment in Controlled Space, pronounced "hocus", as in "hocus-pocus"). But undoubtedly the best recognized is the one applied to himself-TV-by which he was affectionately known, addressed, and referred to. Geodesy was not TV's monolithic preoccupation. After retirement he renewed his interest in his native language and wrote general articles and poetry in Polish. He loved music and taught himself to play the piano, violin and mandolin. He enjoyed a happy family life with his wife, Barbara, his three children, and, subsequently, three grandchildren. At his funeral service, his son Michael gave a touching eulogy and recounted a recent conversation with his father. Recalling the tragic events of his youth and the physical handicaps of his later years, Michael said that he must have had a difficult life. "No", TV replied "I had a colorful life". It was also a very productive life for the science of geodesy.

Bernard Chovitz

Meeting report.

Report of the International Congress on Geodesy and Cartography, Caracas, Venezuela

18-22 March, 2002 (IAG sponsored)

Co-Sponson: Instituto Geográfico de Venezuela Simón Bolívar (DIGECAFA), Dirección de Hidrografía y Navegación (DHN), Fundación Venezolana de Investigaciones Sismológicas (FUNVISIS), Petróleo de Venezuela (PDVSA), Sociedad Venezolana de Ingenieros Geofísicos (SOVG), Instituto Nacional de Canalizaciones (INC), Colegio de Ingenieros de Venezuela (CIV), Asociación Venezolana de Ingenieros Geodestas (ASOVIG),

Organized by: Venezuelan Association Of Geodetic Engineers (ASOVIG)

General Program

Opening Ceremony, Session I and II –Reference Systems, Geoid, Session III and IV–Satellite Techniques, Session V and VI –Geographical Information Systems, Session VII–Cadastre, Session VIII –Interdisciplinary Applications, Session IX–Photogrammetry and Cartography, Session X–Cartography and Remote Sensing, Session XI–Remote Sensing, Session XII–Geodetic Measurements in Engineering

Statistics

There were 72 oral paper presentations from 123 Authors, 62 University students, and 152 registrated participants.

Oral presentations:

In the following, there were presented 72 individual and multinomial papers. The paper titles and their authors are (not in chronological and schematic order):

Acuña (Venezuela), Bosch (Germany): Improving comparisons of satellite altimeter observations and tide gage registrations for unifying height systems in the Caribbean area. Alves, Blitzkow, (Brazil): Modern concepts and techniques of control and forms to monitor tide gage stations with GPS. Alves, Blitzkow, et al. (Brazil): Sea level determination 1831 and 2000 with GPS, leveling and tide gage observations. Arrieche, (Venez): Experiences of hiperspectral remote sensing in the Venezuelan Oil Industry. Azcarate, Martinez, et al., (Venez): Design and application of an interactive system of digital images. Blanco, Gajardo, et al., (Venez): Geotechnical, geophysical and hydraulic studies to define the stability of Mamo Mesa Venezuela. Blanco, Gajardo, et al., (Venez): Observation system of Viaduct No.1 of highway Caracas-La Guaira. Orlando, Barromé, (Venez): Geodetic and instrumental control of the Hydroelectrical Complex of the Lower Caroni River. Buyana, Guevara, et al., (Venez): Methology of Geoid ondulation determination with heterorgenic geodetic data. Clayton, Jacques, et al., (Brazil): Methodology to locate the most favorable areas for installation of small hydropower systems in a GIS environment. Cardozo, Núñez, et al., (Brazil): Orthomosaic generation from a digital, nonmetric camera. Carvalho., et al., (Brazil): Methology for hydraulic works registration of Bahia State, Brazil. Carvalho, et al., (Brazil): Fluvial dynamics of Sao Francisco River using Landsat 7/ETM + images. PimenteL et al., (Brazil): Digital cartography for management of water distribution networks. Pimentel, Ferreira, (Brazil): Teodoro Sampaio and the beginning of systematic cartography in Brazil. Pimentel, Nero, (Brazil): Cartographic documents: Determination of geometric quality in Brazil. Correa E Castro, Blitzkow, (Brazil): Recovery of South American gravity nets by Chile and Paraguay. Daal, Balcázar, et al. (Venez), TREMEL (Germ): GPS Campaign REGVEN 2000. Carvalho et al. (Brazil): Geobotanical analysis of geological structures using hyper spectral images. Cogliano, Galban, et al., (Argentina): First comparison of height networks between Chile and Argentina. Laura Delgado et al. (Venez): Remote Sensing – Digital terrain models and GIS: Tools for Malaria control. Do Nacimiento et al. (Brazil): Morphologic analysis of the Grande River basins as subsidy for ecological zoning using GIS. Dolande, Montezuma, et al. (Venez): Cartographic cover of Esequibo territory by Landsat TM and ETM. Dominguez et al., (Venez): Calibration of position equipments for offshore seismic surveys. Fontes, et al., (Brazil): Use of GIS in management of National Park in Brasilia. Francoso, et al., (Brazil): GIS for historical rescue. Francoso, et.al., (Brazil): GIS en Sao Paulo State. Freitas, et al., (Brazil): Cartographic actualization with IKONOS, using IKONOS 2 satellite for cartographic actualization in maps up to 1:2500. Fuenmayor, et al., (Venez): SIRGAS – REGVEN point densification for PDVSA. Gechele, Nixon, et al., (Venez): GIS implantation by GPS in coastal areas of Maracaibo lake. There were considered Hydro Pro, Pathfinder Office, Auto Cad and Arcview. Gonzalez, Digecafa, (Venez): Evaluation of quick static positioning for medium distances. Guerra, et al., (Venez): The homogeneous treatment unit (UHT), an SIG tool for perforation dispositions.Guevara, et al., (Venez): Evaluation of precision of image orthorectification of IKONOS Satellite in urban areas of Caracas. Guillen, et al., (Venez): System implantation and proof for vehicle control by GPS. Henneberg (Venez): Geodetic measurements of neotectonics and recent crustal movements. Hernandez, (Venez): Evolution and actual situation of Venezuelan geocentric reference system. Hoyer, Hernandez, et al., (Venez): Geoid determination in Venezuela by minimum square collocation. Hoyer, et al., (Venez): GPS measurements processing of REGVEN project. Hoyer, et al., (Venez): RENDON: GPS measurements in the area of the Yacambú-Quibor hydraulic system. Jauregui, et al., (Venez): Elaboration of digital stereo-orthophotos. Liberal, (Venez): Three dimensional geodetic model and GPS application. Lopez, et al., (Venez): Optimization of GPS applications in the Venezuelan Oil Industry. Marquez, Mecinca, (Venez): DIN 18723 and application for certification of theodolites and level instruments Martin, et al., (Venez): Impact of the new official DATUM of Venezuela (SIRGAS – REGVEN ) in geodetic activities of PDVSA. Alves, Pimentel, (Brazil): Digital terrain model. Nero, Pimentel, (Brazil): Map digitalizations: Comparitive studies of methodologies. Ordóñez, et al., (Colombia): Deformation measurements of GALERAS Volcano, Colombia. Ordóñez, et al., (Colombia): GPS measurements for micro gravity studies of Galeras volcano, Colombia. Mora, et al., (Colombia): Satellite geodesy for tectonic deformation measurements in NE of South America. Oropeza, (Venez): Digital rural cadastre of watering systems in Falcón State, Venezuela. Rincon, Et Al., Hoyer, et al., (Venez): Satellite altimeter studies of the Atlantic Front of Venezuela Rios, (Venez): GIS tendency in geography. Rivas, et al., (Venez): GIS for sub terrain installations in urban areas. Rivas, et al., (Venez): Use and methology of multimedia to execute technical evaluation of road communication systems. Rivas, et al., (Venez): Measurements, analysis and composition of the atlas of road systems. Rivas, et al., (Venez): Application of ISO VALUE Lines for residential buildings using a GIS system. Stamato, (Brazil): Is an electronic atlas a geographic information system? Swanston, (Venez): An approximation to a new cadastral registration system. Swanston, (Venez): Quality control of radar orthoimagery. Taylhardat, Hernandez, (Venez): GIS-Exploration processes. Vallee, Parra, (Venez): Cartography of hydrocarbon emanations. PRAOG, TIESZEN, (USA): Development of exploration, access and dissemination of geospace data (clearinghouse) in different Central American countries caused by hurricane Mitch.Vera, et al. (Venez): Geomorphological vision of North and South America. Wildermann, et al., (Venez): Comparison of different height systems in Venezuela. Gavel (USA): Data evaluation for space positioning for oil wells.

Special presentations:

Henneberg, (Venez): Marine Geodesy. Drewes, (Germ): Why do we need a new height system? Guevara, (USA): The Geospace paradigm and its impact on a bearable progress. Rendon, (Venez): The project for modernization of the national seismology network. Drewes, (Germ): The international reference system ITRF and its continental amplification (SIRGAS). Vera, (Venez): Technological promotion – Air transportable remote system for “Alto Resources Venezuela, C.A.” Prelat, (USA): Hyper spectral technology for evaluation of national resources and environment.

Heinz Henneberg, National IAG Representative

Book Review.

The Measurement of Time

title: The Measurement of Time - Time, Frequency and the Atomic Clock

authors: Claude Audoin and Bernard Guinot

publisher: Cambridge University Press

ISBN: 0-521-80080-3 / 0-521-00397-0

year: 2001

price: GBP 75 / GBP 27.95

pages: 335

size: 15 x 23 cm

details: hardback /paperback

It may seem far away and long ago to younger scientists, but many of us still remember when the Time Lords of the 1970’s advanced the Copernican revolution by defining frequency in terms of atomic standards rather than by the Earth’s motion. Since then, the accuracy and precision of atomic standards have improved by orders of magnitude, as has our ability to measure and understand the variations of the Earth’s rotation.

‘The Measurement of Time’ describes current atomic timekeeping metrology in a pleasing and technically correct manner. It is not a textbook; it is an ideal introductory book for graduate students and researchers interested in time and frequency, and would be very useful for people specializing in any related field. The emphasis is on atomic timekeeping metrology, but it also contains sections on the Earth’s rotation that would be of direct relevance to both geodesists and science historians.

There are no people more fitting to summarize the timekeeping field than the book’s authors, Drs. Audoin and Guinot, who helped shape many of the developments covered in the book. Claude Audoin was director of the Laboratoire de l’Horloge Atomique, and has been an active contributor since he received his doctorate in 1967. He has published numerous works, and coauthored a two-volume high-level text on quantum physics that can be found in every atomic physics laboratory. Bernard Guinot started working with the Paris Observatory in 1952, and went on to become the director of the Bureau International de l’Heure (BIH), which was then the official institution for reporting time as measured by Earth rotation and as measured by clocks. He personally published many of the timescale algorithms that are in use today, and his papers continue to be referenced. Stephen Lyle’s translation is so smooth that one must read the cover pages to know the book was originally written in French.

The book’s strongest point is that it provides excellent coverage of the fundamental physics behind the most precise clocks of modern times, including atomic beams, atomic fountains, masers, and trapped ions. There is a thorough analysis of the many error sources that contribute to these atomic frequency standards, which is complemented by coverage of design improvements that either reduce the errors or allow their instrumental calibration. Almost half of the 331-page book is devoted to atomic standards and their many interesting complexities, but the authors also emphasize that even the most stable and best-calibrated clock is not immune to the Special and General Theories of Relativity. On the Earth’s surface, the gravitational red shift will change a clock’s frequency by 1.E-16 per vertical meter. Clocks that exist only on today’s viewgraphs may in tomorrow’s laboratories require analysis of the differential relativistic effects within their own chassis. This book provides an excellent introduction to all of these concepts, as well as 14 pages of references to the literature.

Most readers will enjoy the many items that are briefly, but succinctly covered. The historical snippets from pre-atomic timekeeping provide flavor. The reasons for the Earth’s irregular rotation and the different types of rotational time (UT0, UT1, UT2, UT1R, and UT1R’) are clearly described. Equally useful definitions of the atomic time scales relativistically referenced to the geocenter or the solar system’s barycenter are also provided. The description of statistical metrics for measuring clock stability, such as the Allan variance, is logical and straightforward; however, the reader should be advised that the choice of the metric depends as much on the problem under consideration as on the need to avoid mathematical divergences. It might spare some beginners a few misconceptions if they could read the description of how International Atomic Time (TAI) is actually computed today by the Bureau International de Poids et Mesures (BIPM). The four pages devoted to pulsars shows how they can never replace atomic clocks, could perhaps complement them, and have supported General Relativity by providing indirect evidence of gravitational radiation. The final chapter, on applications, shows how clocks contribute to our understanding of quantum physics directly as sensors and indirectly as enabling technologies; how clocks contribute to navigation; and how they are used in the telecommunications industry.

The authors have strived to be as current as possible, apparently taking advantage of the language-translation delay to insert a description of the International Astronomical Union (IAU) resolutions of August 2000, which removed the geoid as a reference for the definition of Terrestrial Time and called for a ‘non-rotating’ origin for the Celestial Intermediate Pole. But in the rapidly developing field of timekeeping it is inevitable that some parts of any text will quickly become out of date. The mathematics of N-cornered-hat stability analysis has been extended to cover correlations between clocks. The researchers at Jet Propulsion Laboratories (JPL) have improved their linear ion trap by shuttling ions between different regions and by adopting a multi-pole trap geometry. Figure 8.7 does not show the pulsar instabilities revealed by the latest data; however, this does not change the conclusions in the text. Time transfer, which is not emphasized in the book, has improved greatly through use of carrier-phase GPS techniques. With the advent of carrier-phase Two-Way Satellite Time Transfer, it is likely that even this review will be out of date before it is published.

Dr. Demetrios Matsakis, Time Service Department of the U.S. Naval Observatory

(whose Master Clock is the time reference for GPS)