scholarly journals Origin and Scale of Coordinate Systems in Satellite Geodesy

1980 ◽  
Vol 56 ◽  
pp. 239-250
Author(s):  
J. B. Zieliński
Keyword(s):  
Coordinate System ◽  
Inner Core ◽  
Center Of Mass ◽  
Point Of View ◽  
Satellite Geodesy ◽  
Coordinate Systems ◽  
Scale Problem ◽  
The Earth ◽  
Geocenter Motion

AbstractThe center of mass of the Earth is commonly taken as origin for the coordinate systems used in satellite geodesy. In this paper the notion of the “geocenter” is discussed from the point of view of mechanics and geophysics. It is shown that processes in and above the crust have practically no impact on the position of the geocenter. It is possible however that motions of the inner core may cause variations of the geocenter of the order of 1 m. Nevertheless the geocenter is the best point for the origin of a coordinate system. Mather’s method of monitoring geocenter motion is discussed, and some other possibilities are mentioned. Concerning the scale problem, the role of the constant GM and time measurements in satellite net determinations are briefly discussed.

scholarly journals On the Absolute Orientation of the Selenodetic Reference Frame

1981 ◽  
Vol 63 ◽  
pp. 281-286
Author(s):  
V. S. Kislyuk
Keyword(s):  
Coordinate System ◽  
Center Of Mass ◽  
The Moon ◽  
Coordinate Systems ◽  
Inertial Coordinate System ◽  
Reference Coordinate System ◽  
The Earth ◽  
Principal Axes ◽  
The Mean ◽  
Selection Of

The selection of selenodetic reference coordinate system is an important problem in astronomy and selenodesy. For the purposes of reduction of observations, planning and executing space missions to the Moon, it is necessary, in any case, to know the orientation of the adopted selenodetic reference system in respect to the inertial coordinate system.Let us introduce the following coordinate systems: C(ξc, ηc, ζc), the Cassini system which is defined by the Cassini laws of the Moon rotation;D(ξd, ηd, ζd), the dynamical coordinate system, whose axes coincide with the principal axes of inertia of the Moon;Q(ξq, ηq, ζq), the quasi-dynamical coordinate system connected with the mean direction to the Earth, which is shifted by 254" West and 75" North from the longest axis of the dynamical system (Williams et al., 1973);S(ξs, ηs, ζs), the selenodetic coordinate system, which is practically realized by the positions of the points on the Moon surface given in Catalogues;I(X,Y,Z), the space-fixed (inertial) coordinate system. All the systems are selenocentric with the exception of S(ξs, ηs, ζs On the whole, the origin of this system does not coincide with the center of mass of the Moon.

Reference Coordinate System Requirements for Geophysics

1975 ◽  
Vol 26 ◽  
pp. 87-92
Author(s):  
P. L. Bender
Keyword(s):  
Coordinate System ◽  
Polar Motion ◽  
Main Part ◽  
Measurement Techniques ◽  
Reference Points ◽  
Angular Motion ◽  
Coordinate Systems ◽  
Axis Of Rotation ◽  
The Earth ◽  
Fixed System

AbstractFive important geodynamical quantities which are closely linked are: 1) motions of points on the Earth’s surface; 2)polar motion; 3) changes in UT1-UTC; 4) nutation; and 5) motion of the geocenter. For each of these we expect to achieve measurements in the near future which have an accuracy of 1 to 3 cm or 0.3 to 1 milliarcsec.From a metrological point of view, one can say simply: “Measure each quantity against whichever coordinate system you can make the most accurate measurements with respect to”. I believe that this statement should serve as a guiding principle for the recommendations of the colloquium. However, it also is important that the coordinate systems help to provide a clear separation between the different phenomena of interest, and correspond closely to the conceptual definitions in terms of which geophysicists think about the phenomena.In any discussion of angular motion in space, both a “body-fixed” system and a “space-fixed” system are used. Some relevant types of coordinate systems, reference directions, or reference points which have been considered are: 1) celestial systems based on optical star catalogs, distant galaxies, radio source catalogs, or the Moon and inner planets; 2) the Earth’s axis of rotation, which defines a line through the Earth as well as a celestial reference direction; 3) the geocenter; and 4) “quasi-Earth-fixed” coordinate systems.When a geophysicists discusses UT1 and polar motion, he usually is thinking of the angular motion of the main part of the mantle with respect to an inertial frame and to the direction of the spin axis. Since the velocities of relative motion in most of the mantle are expectd to be extremely small, even if “substantial” deep convection is occurring, the conceptual “quasi-Earth-fixed” reference frame seems well defined. Methods for realizing a close approximation to this frame fortunately exist. Hopefully, this colloquium will recommend procedures for establishing and maintaining such a system for use in geodynamics. Motion of points on the Earth’s surface and of the geocenter can be measured against such a system with the full accuracy of the new techniques.The situation with respect to celestial reference frames is different. The various measurement techniques give changes in the orientation of the Earth, relative to different systems, so that we would like to know the relative motions of the systems in order to compare the results. However, there does not appear to be a need for defining any new system. Subjective figures of merit for the various system dependon both the accuracy with which measurements can be made against them and the degree to which they can be related to inertial systems.The main coordinate system requirement related to the 5 geodynamic quantities discussed in this talk is thus for the establishment and maintenance of a “quasi-Earth-fixed” coordinate system which closely approximates the motion of the main part of the mantle. Changes in the orientation of this system with respect to the various celestial systems can be determined by both the new and the conventional techniques, provided that some knowledge of changes in the local vertical is available. Changes in the axis of rotation and in the geocenter with respect to this system also can be obtained, as well as measurements of nutation.

3. Minerals and the interior of the Earth

2014 ◽  
Author(s):  
David Vaughan
Keyword(s):  
Upper Mantle ◽  
Lower Mantle ◽  
Plate Tectonics ◽  
Inner Core ◽  
Indirect Evidence ◽  
Outer Core ◽  
The Earth ◽  
Granite Formation ◽  
Temperature And Pressure

‘Minerals and the interior of the Earth’ looks at the role of minerals in plate tectonics during the processes of crystallization and melting. The size and range of minerals formed are dependent on the temperature and pressure of the magma during its movement through the crust. The evolution of the continental crust also involves granite formation and processes of metamorphism. Our understanding of the interior of the Earth is based on indirect evidence, mainly the study of earthquake waves. The Earth consists of concentric shells: a solid inner core; liquid outer core; a solid mantle divided into a lower mantle, a transition zone, and an upper mantle; and then the outer rigid lithosphere.

The Estimation and Prediction of Geocenter Motion Based on GNSS Weekly Solutions

2020 ◽  
Author(s):  
Chunmei Zhao ◽  
Lingna Qiao ◽  
Tianming Ma
Keyword(s):  
Reference Frame ◽  
Prediction Accuracy ◽  
Center Of Mass ◽  
Science Research ◽  
Terrestrial Reference Frame ◽  
Small Contribution ◽  
The Earth ◽  
Term Prediction ◽  
Geocenter Motion

<p>The development of satellite space geodesy technology makes the establishment of global terrestrial reference frame based on the Earth’s center of mass become reality. Precise and stable terrestrial reference frame is the foundation of the Earth science research, while determination and analysis of the position of the Earth's center of mass and its change is an important part to build high precision terrestrial reference frame. Based on GNSS weekly solutions provided by IGS, the geocenter motion (GM) time series between 2007 and 2017 are obtained by means of net translation method. Then the amplitude of the annual term of geocentric motion is 2.27mm, 1.84mm and 2.13mm in the direction of X, Y and Z respectively, and the amplitude of the half-year term is 0.1mm, 0.20mm and 0.15mm respectively. In addition, some other inter-annual changes with relatively small contribution rate are found. Finally, in order to get reliable GM prediction ,two kinds of methods are used, which are ARMA and SSA+ARMA. In the short-term prediction, the accuracy of the two methods is the same, both can reach the millimeter level of prediction accuracy, but SSA+ARMA is more stable. SSA+ARMA algorithm is much better in the medium and long-term scale, and it can provide 1mm medium term prediction accuracy and 1.5mm long term prediction accuracy.</p>

scholarly journals Reference Coordinate Systems for Earth Dynamics: A Preview

1980 ◽  
Vol 56 ◽  
pp. 1-22 ◽  
Author(s):  
Ivan I. Mueller
Keyword(s):  
Coordinate System ◽  
Coordinate Systems ◽  
Inertial Coordinate System ◽  
Terrestrial System ◽  
The Earth ◽  
Earth Dynamics

AbstractA common requirement for all geodynamic investigations is a well-defined coordinate system attached to the earth in some prescribed way, as well as a well-defined inertial coordinate system in which the motions of the terrestrial system can be monitored. This paper deals with the problems encountered when establishing such coordinate systems and the transformations between them. In addition, problems related to the modeling of the deformable earth are discussed.

scholarly journals Specific aspects of globalization

2008 ◽  
Vol 53 (No. 2) ◽  
pp. 65-68 ◽  
Author(s):  
M. Svatoš
Keyword(s):  
Sustainable Development ◽  
Decisive Role ◽  
Adaptation Strategy ◽  
Point Of View ◽  
Human Society ◽  
Human Adaptation ◽  
Negative Effects ◽  
The Earth ◽  
Global Problems

The decisive role of globalization processes and development tendencies has many positive and negative effects in economic (foreign-trade), environmental, and (bio) technological areas. From the evolution point of view still very successful human adaptation strategy hit the basic limit given by the capacity of the Earth biosphere. The evolution determinants of human society and their economic or technological activities manifesting themselves by global problems can find way out of sustainable development. The application of the so-called preventive principle represents a great dilemma.

Nature of the Requirements for Reference Coordinate Systems

1975 ◽  
Vol 26 ◽  
pp. 49-62
Author(s):  
C. A. Lundquist
Keyword(s):  
Rigid Body ◽  
Coordinate System ◽  
Equations Of Motion ◽  
Inertial Reference Frame ◽  
Earth System ◽  
Coordinate Systems ◽  
Dynamical Equations ◽  
The Earth ◽  
Measurement Uncertainties ◽  
Rotational Motions

AbstractThe current need for more precisely defined reference coordinate systems arises for geodynamics because the Earth can certainly not be treated as a rigid body when measurement uncertainties reach the few centimeter scale or its angular equivalent. At least two coordinate systems seem to be required. The first is a system defined in space relative to appropriate astronomical objects. This system should approximate an inertial reference frame, or be accurately related to such a reference, because only such a coordinate system is suitable for ultimately expressing the dynamical equations of motion for the Earth. The second required coordinate system must be associated with the nonrigid Earth in some well defined way so that the rotational motions of the whole Earth are meaningfully represented by the transformation parameters relating the Earth system to the space-inertial system. The Earth system should be defined so that the dynamical equations for relative motions of the various internal mechanical components of the Earth and accurate measurements of these motions are conveniently expressed in this system.

Role of Artificial Earth Satellites in Redefinition of the North American Datum

1974 ◽  
Vol 28 (5) ◽  
pp. 590-597 ◽  
Author(s):  
Richard J. Anderle
Keyword(s):  
Reference Frame ◽  
North American ◽  
Center Of Mass ◽  
Satellite Observations ◽  
The North ◽  
Artificial Earth Satellites ◽  
The Earth ◽  
Artificial Earth ◽  
Terrestrial Network

Satellite observations provide a reference frame for terrestrial survey whose origin is within one metre of the center of mass of the earth, whose z-axis is parallel to the CIO pole to the equivalent of five metres at the earth’s surface, and whose scale has an accuracy of about a part per million. A convention needs to be adopted to define the longitude origin. A well adjusted terrestrial network can be transformed to this system to about one-metre accuracy. Densification of the terrestrial network can be accomplished to 1.5 metre accuracy with the use of less than four days of Doppler observations for each site.

Terrestrial Coordinate Systems Solidly Connected with the Earth

1975 ◽  
Vol 26 ◽  
pp. 133-159
Author(s):  
M. Bursa
Keyword(s):  
Center Of Mass ◽  
Coordinate Systems ◽  
Basic Definition ◽  
The Earth ◽  
Satellite Methods ◽  
Definition Of ◽  
Actual Accuracy

AbstractThe principles and the suppositions for the basic definition of terrestrial coordinate systems solidly connected with the Earth are discussed: Problem of determining the position of the Earth’s center of mass (or of the centers of geodetic reference ellipsoids). Problem of defining the conventional geocentric and geodetic reference axes as well as axes of the principal terrestrial ellipsoid of inertia. Problem of determining directions of geodetic reference axes using geometrical satellite methods and the actual accuracy of the solution.

2.1. Working Group 1: Requirements for Coordinate Systems for Earth Dynamics

1975 ◽  
Vol 26 ◽  
pp. 15-20
Keyword(s):  
Coordinate System ◽  
Working Group ◽  
Global Scale ◽  
Coordinate Systems ◽  
Tectonic Plates ◽  
The Earth ◽  
International Projects ◽  
The Subject ◽  
Earth Dynamics ◽  
Group 1

As initial guidance for its deliberations, Working Group 1 accepted the objective implied in the Colloquium title and the more explicit description contained in the First Circular announcing the Colloquium:Earth dynamics is currently the subject of intensive world-wide research efforts. As a consequence of the new insights into Earth dynamics and acceptance of the hypothesis of moving tectonic plates, as well as the ability to measure crustal motions on a global scale with a precision of a few centimeters, a number of national and international projects have been organized to pursue these investigations. In all these efforts, a common feature is the necessity for a very well defined coordinate system to which all observations can be referred and in which theories can be formulated. At this time there is no widely accepted coordinate system in the Earth or in space which is defined with the precision needed for ongoing geodynamics research.

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