摘要:

The growing interaction of geodesy with its kindred disciplines, oceanography and tectonophysics, may have been the most significant trend in geodetic activity during this past quadrennium. Geodetic observing systems are now capable of measuring so much more precisely (to the centimeter level) and over such a broader extent (like the oceans), that their results add materially to knowledge of crustal and mantle structure, of ocean bottom relief, and of oceanic circulation. Especially important is the application of precise, repetitive geodetic measurements to the detection and analysis of time‐varying effects. Examples are the utilization of altimeter data to yield ocean boundary current changes, and of radio interferometry and laser ranging to systematically monitor polar motion, Earth rotation, and crustal movement

ISSN:8755-1209    

DOI:10.1029/RG021i003p00521

年代:1983

数据来源: WILEY

摘要:

North American Datum (NAD) Readjustment Project. The NAD readjustment project of the National Geodetic Survey (NGS) consists of three major tasks: the validation of all field projects, the validation of individual blocks, and the solution of the equations associated with each observation. Associated tasks include: researching mathematical models, defining detailed procedures, and developing required software. The validation of 4,890 field projects involved the keying of 2.5 million direction observations, the reprocessing of 60,000 electronic distance measurements, and the separate least‐squares adjustment of each field project.Block validation consists of the systematic analysis of observational data within more than 800 blocks. This task began in July 1982, and is expected to continue for 2 years. The partitioning of the U.S. horizontal network into blocks, and the systematic reduction of the equations by the Helmert blocking method, represents the last task of the project. Block validation testing began in the fall of 198

ISSN:8755-1209    

DOI:10.1029/RG021i003p00523

年代:1983

数据来源: WILEY

摘要:

This report, which follows the general format of reports by J. D. Anderson [1975] and W. H. Michael [1979], deals with geodetic parameters of the planets and their satellites (including the Moon but not the Earth): shape, rotation, orientation, and gravity. A paper by Ferrari and Bills [1979] covers similar material as Michael [1979], but contains additional comments on geophysics. Three review articles, which provided a helpful base for the references reported here, are Harris and Ward [1982], Phillips and Lambeck [1980], and Balmino [1981]. A very basic document covering all planetary bodies and their satellites is the report of the International Astronomical Union Working Group [Davies, et al, 1982], which provides new values for cartographic coordinates, orientations, and rotations.

ISSN:8755-1209    

DOI:10.1029/RG021i003p00528

年代:1983

数据来源: WILEY

摘要:

The details of progress in United States gravimetry during the period 1979–82, reported below, have been compiled largely from unpublished reports, personal communications to the authors and the authors' own knowledge of recent developments. A representative sampling of important literature published during the period is included.Recent developments in gravimetry in the United States are highlighted by the development and deployment of a new portable absolute gravity apparatus, a rebirth of airborne gravimetry in the form of an accurate operational helicopter gravity measuring system, the impending fabrication of a superconducting gravimeter for geodetic surveys, and the establishment of a new long‐range calibration l

ISSN:8755-1209    

DOI:10.1029/RG021i003p00537

年代:1983

数据来源: WILEY

摘要:

In 1979, Farrell (1979) pointed out that investigators in all areas of earth tide studies were recognizing the importance of the inherent connection between the solid tidal response and that of the oceans to the same solar and lunar gravitational attractions. Since then, the use of ocean tide models determined from solutions of Laplace tidal equations (Parke and Hendershott, 1979) and solutions which incorporate a global distribution of tide gauge results (Schwiderski, 1979a, 1979b, 1980, 1982e) in the analysis of earth tide gravity data and satellite perturbations in the semi‐diurnal and diurnal bands have become a common operation. Results are available for most major semi‐diurnal, diurnal, and long period tidal constituents. Studies of the response of the earth's rotation to the long period tides have also been performed (Yoder et al. 1981a

ISSN:8755-1209    

DOI:10.1029/RG021i003p00544

年代:1983

数据来源: WILEY

摘要:

Spurred by a tremendous increase in new and highly accurate data and by prospects for further improvements, theoretical studies in geodesy have concentrated on devising new methods, or adapting extradisciplinary ones, to process the data efficiently and accurately. Satellite altimetry, the NAVSTAR Global Positioning System, satellite Doppler, satellite‐to‐satellite tracking, satellite laser, VLBI, satellite interferometry, and inertial navigation advancements are all contributing to provide the geodetic, and indeed the geophysical, community with a wealth of new data. Least‐squares collocation has achieved prominence through numerous applications, but for efficiency it must compete with other methods, such as those founded in spectral theory. Also, the improved measurement accuracy has mandated the development of more realistic geodetic models where former approximations can no longer be tole

ISSN:8755-1209    

DOI:10.1029/RG021i003p00547

年代:1983

数据来源: WILEY

摘要:

The past four years have been a paradoxical watershed for the geodetic measurement of contemporary crustal motion in the U.S. More than ever before, the role of systematic errors in the techniques used to monitor crustal movement has been a major issue. Yet while concern was growing over such errors in some studies, other measurements were reaffirming the unique and effective contribution of geodetic techniques to geodynamic investigation by confirming previously mapped patterns of crustal deformation as well as providing exciting evidence of movement in previously unstudied areas. With new efforts to understand and minimize the influence of errors, to resurvey substantial portions of the U.S. geodetic network, to computerize historical geodetic measurements, and to bring online new space‐based geodetic systems well underway, geodesy is certain to play an increasingly important role in the investigation of contemporary tectonic

ISSN:8755-1209    

DOI:10.1029/RG021i003p00553

年代:1983

数据来源: WILEY

摘要:

Substantial progress has been made in modeling the geopotential field since the last reporting period (Anderle, 1979a). Models of the gravity potential show improvement across the entire gravitational spectrum with resolution down to 1° haIf‐wavelength. Major sources of data utilized for advancing our knowledge of the geopotential field consist of satellite laser ranging (Smith, 1982; Wilson, 1979; Linder, 1981) which contributed to the long wavelength portion of the spectrum, satellite altimetry (GEOS‐3, 1979; SEASAT, 1981) and improved surface gravity anomalies (Rapp, 1981b) both of which contributed to the intermediate and short wavelength features of the spectrum. Uniform global distribution of data in combination solutions is generally achieved by using altimeter data over the ocean and terrestrial gravity anomalies over

ISSN:8755-1209    

DOI:10.1029/RG021i003p00560

年代:1983

数据来源: WILEY

摘要:

In the previous Quadrennial Report, Clark [1979c] concluded that, after slightly more than one decade of development and refinement, the technique of Very Long Baseline Interferometry (VLBI) had “come of age.” However, by the close of 1978, only the most tentative first steps had been taken by the geodetic community toward the deployment and operation of VLBI geodetic surveying systems. There was not a single dedicated geodetic VLBI observatory in the world. Even at major astronomical observatories, geodetic VLBI observing sessions were elaborate productions involving the very scientists and engineers who designed and built the instrumentation operating the data acquisition syst

ISSN:8755-1209    

DOI:10.1029/RG021i003p00565

年代:1983

数据来源: WILEY

摘要:

During the period from 1979 through 1982, polar motion and earth rotation activity centered on the development of new observation techniques and the investigations of the relation between the observed motions and geophysical phenomena. Determinations of polar motion through classical techniques continued, but the number of United States observing sites was reduced. However, significant advances in alternate methods for polar motion and earth rotation determination were achieved. Regular polar motion and length of day determinations are being reported now by groups analyzing satellite doppler, laser ranging and very long baseline interferometry (VLBI) data, and preliminary determinations of UT1 by these methods are now being reported.

ISSN:8755-1209    

DOI:10.1029/RG021i003p00569

年代:1983

数据来源: WILEY