Showing papers on "Geodetic datum published in 1979"

On the analysis of geodetic networks for the determination of the incremental strain tensor

Abstract: A method is developed for the determination of the incremental strain tensor from repeated geodetic measurements. In principle, the method is based on the changes of the co-ordinates of a geodetic network placed in a homogeneous strain field. It provides for the incorporation of all types of geodetic measurements. The inner co-ordinates and the inner precision of the common points at both epochs are used for the least squares estimation of the increlnental strain tensor. A statistical test is designed to test for the significance of homogeneous incremental strain.

Satellite Emission Radio Interferometric Earth Surveying SERIES-GPS Geodetic System

Abstract: The satellites of the Global Positioning System (GPS) offer an important new geodetic resource making possible a highly accurate portable radio geodetic system A concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) makes use of GPS radio transmissions without any satellite modifications By employing the technique of very long baseline interferometry (VLBI) and its calibration methods, 05 to 3 cm three dimensional baseline accuracy can be achieved over distances of 2 to 200 km respectively, with only 2 hours of on-site data acquisition The use of quasar referenced ARIES Mobile VLBI to establish a sparse fundamental control grid will provide a basis for making SERIES GPS measurements traceable to the time-invariant quasar directions Using four SERIES stations deployed at previously established ARIES sites, allows the GPS satellite apparent positions to be determined These apparent positions then serve as calibrations for other SERIES stations at unknown locations to determine their positions in a manner traceable to the quasars Because this proposed radio interferometric configuration accomplishes its signal detection by cross-correlation, there is no dependence upon knowledge of the GPS transmitted waveforms which might be encrypted Since GPS radio signal strengths are 105 stronger than quasar signals, a great reduction in telecommunications sophistication is possible which will result in an order of magnitude less cost for a SERIES GPS station compared to a quasar based mobile VLBI system The virtually all-weather capability of SERIES offers cost-effective geodetic monitoring with applications to crustal dynamics and earthquake research

Concepts in Geodetic Reference Frames.

Abstract: : The report reviews conceptual aspects and problems arising in a precise definition of reference frames for the purpose of geodesy and geodynamics. The concepts: physical, conventional, and average system are introduced. Inertial systems are discussed from the point of view of classical mechanics and of the theory of relativity. The concept of celestial pole, which plays a fundamental role in a precise definition of precession, nutation and polar motion, is reviewed in some detail. A section is devoted to tidal effects, which should be removed from the coordinates. Finally, various definitions of terrestrial reference systems are compared. (Author)

Techniques and Problems in Geodetic Monitoring of Crustal Movements at Tectonically Unstable Regions

Abstract: The possibilities and limitations of the contribution of geodetic methods for the monitoring of secular crustal dynamics are discussed in view of plate tectonics and of local crustal deformations related with the earthquakes. Topics concerning the calculation of long-term strain frcm geodetic results are stressed in connection with short-term strain information obtained by geophysical instrumentation and reliability problems associated with the design of geodetic operations are as well underlined. A brief discussion on the necessity of applying geodetic methods as integrating factor for crustal deformation studies as far as the Hellenic tectonically anstable region is concerned, concludes the paper.

Dynamic satellite geodesy

Abstract: The paper describes operation of the GEOS-3 and Lageos spacecraft launched by NASA as part of the Earth and Ocean Dynamic Program. The investigations conducted by using GEOS-3 include the determination of tracking station coordinates, polar motion, and the use of altimetry in orbit determination. Lageos was designed as a precision target for making geodetic measurements with ground laser systems. Consideration is given to the progress made in the investigation and determination of tidal parameters by means of satellite perturbation methods. Satellite geodetic methods based on the ability to determine precise satellite orbits and orbit determination are outlined. Emphasis is placed on the future studies employing Spaceborne Laser and Global Positioning System concepts.

Solution of the geodetic boundary value problem

Abstract: The possibility of improving the convergence of Molodensky’s series is considered. Then new formulas are derived for the solution of the geodetic boundary value problem. One of them presents an expression for the boundary condition which involves a linear combination of Stokes’ constants and surface gravity anomalies. This differs from the usually used relation by the appearance of additional terms dependent on second order terns with respect to the elevations of the earth’s surface. The formulas are derived for Stokes’ constants and the anomalous potential in terms of surface anomalies. As compared to the Taylor’s series of Molodensky, they are presented in the form of surface harmonic series. Due regard is made to the earth’s oblateness, in addition to the terrain topography.

A Geodetic Micro-Network for Monitoring Tectonic Movements In a Peruvian Earthquake Fault Zone

Abstract: In 1969 a tectonic fault was caused by two earthquakes in the area of Pariahuanca at the foothills of Nevado Huaytapallana, Central Peru. At the suggestion of Peruvian and Canadian geophysicists a geodetic micro-network for monitoring tectonic movements was installed. Repeated observations of high accuracy were carried out from 1975 — 1978; they should figure out whether significant displacements of points and consequently crustal movements had taken place. This report gives some details about the earthquakes, the active fault and the observations, adjustments and accuracies of the Huaytapallana network. Further on general and special remarks are made on geodetic deformation analysis and problems and limits of interpretation including some proposals for future proceeding.

The division of national mapping's part in the geodetic survey of Australia

Abstract: 1965 was to be the concluding year of field work before the adjustment of all loops on the primary geodetic traverses. For details of this National Geodetic Adjustment refer to “The Geodetic Adjustment of Australia, 1963–66” by A. G. Bomford; Survey Review Vol. XIX p. 52 1967, and Technical Report No. 6, “Varycord — A Fortran programme for the least squares adjustment of horizontal control surveys.” by A. G. Bomford, May 1967.

Construction of large space structures

Abstract: The paper examines a construction capability to build large structures in space, its use in conjunction with the Shuttle Orbiter and a large Space Construction Base, and its relationship to system performance and cost. The geodetic beam design using a tetrahedral truss structure and reinforced plastics and its structural analysis, tests of demonstration cylinders, and preliminary machine design are discussed. The geodetic structure is shown to have high buckling stability, low thermal distortion, high stiffness, and its simple shape permits high-production-rate automatic fabrication. The geodetic beam fabrication machine which will automatically fabricate cylindrical beams in space from earth-prefabricated rods, and on-orbit beam and platform fabrication are described. Preliminary results of system performance and cost studies indicate that on-orbit fabrication using a small geodetic beam machine can be economically superior to the deployable and erectable modes of construction for many near term applications.

Error Propagation in Absolute Geodetic Networks.: A Continuous Approach.

Abstract: SummaryStudies of error propagation in geodetic networks of an absolute type have already been carried through by several authors using various mathematical techniques. The geodetic elasticity theory relies on a continuation of the actual, discrete network. The traditional observation and normal equation matrices are substituted by partial differential equations with corresponding boundary conditions. The continuous approach only reflects the global error behaviour opposed to the discrete case, and produces only asymptotic results. An advantage of the method is that we may directly profit from existing mathematical knowledge. The fundamental solution of the partial differential equations acts as a formal covariance function and yields the best linear unbiased estimates for estimable functions of the adjustment parameters. Levelling networks and networks with distance and azimuth measurements are studied in this framework.

Geodetic Surveying: The Next Decade

Abstract: By the end of the next decade (1988), most large-area geodetic surveys will probably be made using a satellite Doppler positioning system, an inertial positioning system, or some combination of the two systems. The Doppler system is capable of determining the absolute, three-dimensional position of any point on the earth and it can also be used to obtain relative positions. Using data from multiple satellite passes and refined data reduction techniques, it is possible to obtain accuracies of 20 cm or better. The development of the Global Positioning System (GPS) in the 1980's is expected to improve position accuracies to 10 cm or better. The inertial system is capable of very large, rapid surveys with position accuracies of 20 cm or better relative to the control used. In addition, deflections of the vertical to one second of arc and gravity anomalies to one milligal can also be obtained. Despite relatively large costs, both systems have proven to be cost-effective because of their very high productivities.

Planetary geodetic control using satellite imaging

Abstract: A new data type for planetary geodetic control using natural satellite imaging is presented. Spacecraft images of natural satellites against the planet give a direct tie between inertial space and surface features surrounding the satellite image. This technique is expected to offer a factor of 3-10 improvement in accuracy over present geodetic reduction for Mars. A specific example using Viking imaging of Phobos against Mars is given.

Redefinition of National Vertical Geodetic Networks

Abstract: A brief review of uses and applications of vertical control points is presented, followed by a description of national leveling networks, which are based on the 1928 Canadian Vertical Datum. Proble...

Introduction to the report on geodesy

Abstract: The achievements of the U.S. geodetic community during the years 1974–1978 between the General Assemblies of the IUGG are summarized in this section. During this quadrennium, American geodesy dramatically moved from the era of primarily meeting the traditional needs of surveying and mapping into one of supporting a broad spectrum of geophysical and planetary disciplines. This movement was aided by modern technology epitomized by the increases in Doppler satellite observations, multifrequency distance measurements, lunar and satellite laser ranging, very long base line interferometry (VLBI), satellite altimetry measurements and inertial positioning. By far the most spectacular achievement in the field of geodesy during this period was the global sampling of sea surface topography with precision radar altimeters aboard the National Aeronautics and Space Administration (NASA) GEOS-3 and Seasat-1 satellites. The GEOS-3 altimetry data set, acquired over a 3-year period (1975–78), significantly improved our knowledge of the global gravity field of the earth, the oceanic geoid and the related mean gravity anomalies. Had the Seasat-1 not failed after 3 months, an even more detailed knowledge of the oceanic geoid would be available today. Even with this early demise, Seasat-1 in 3 months collected more altimetry data with greater accuracy than did GEOS-3 in 3 years.

Possibilities and Limitations of Doppler Positioning in Geodynamics

Abstract: During the past years Doppler positioning by aid of artificial satellites, especially within the US Navy Navigation System, has been introduced into large fields of geodesy. This new technique nowadays is used to determine control points especially in countries where we have no unique first order triangulations, to combine national geodetic networks, to determine transformation parameters for terrestrial networks into geocentric systems and to investigate certain geodynamic aspects such as polar motion and the rotation of the earth. This paper includes a short description of the Doppler measuring technique and of the US Navy Navigation System. Furthermore the accuracy attainable to-day with this new technique is discussed based on comparisons with terrestrial networks. Finally attention is drawn to future systems and their estimated accuracy.