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First Six Months of Superconducting Gravimetry in Argentina
Get PDFOn December 16th, 2015, the superconducting gravimeter SG038 started to measure again after it was moved from the previous station in Concepcion, Chile to the Argentine-Germany Geodetic Observatory (AGGO) near the city of La Plata in Argentina. The temporal gravity variations recorded with superconducting gravimeters (SG) enables research in several geodetic and geophysical studies that involve Earth’s changes in the surface gravity field. In particular, it allows computing local models of earth tide parameters. The superconducting gravimeter SG038 at station AGGO was used to monitor gravity for the first 6 months after its installation. The gravity time series was preprocessed after removing the principal constituents of the largest influences of the gravity signal that can be modeled sufficiently accurate like atmospheric effects, theoretical tides of the solid Earth, ocean loading effects and pole tides. In the remaining residual signal spikes were fixed, earthquake perturbations were reduced. Finally, the theoretical tides of the solid Earth and ocean loading effects previously removed were restored to obtain the corrected gravity signal. The transfer function of the SG038 was determined by analyzing the step response of the whole system. Empirical amplitude and phase response functions are presented. The group delay at zero frequency was used in the tidal analysis. By harmonic analysis of the preprocessed hourly data, amplitude factors and phases for tidal wave groups were estimated.Fil: Antokoletz, Ezequiel Darío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Gravimetría; ArgentinaFil: Wziontek, Hartmut. Federal Agency for Cartography and Geodesy; AlemaniaFil: Tocho, Claudia. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Gravimetría; Argentin
Gravity reference at the Argentinean–German Geodetic Observatory (AGGO) by co-location of superconducting and absolute gravity measurements
Get PDFThe Argentinean–German Geodetic Observatory (AGGO) is a fundamental geodetic observatory located close to the city of La Plata, Argentina. Two high-precision gravity meters are installed at AGGO: the superconducting gravimeter SG038, which is in operation since December 2015, and the absolute gravimeter FG5-227, which has provided absolute gravity measurements since January 2018. By co-location of gravity observations from both meters between January 2018 and March 2019, calibration factor and instrumental drift of the SG038 were determined. The calibration factor of the SG038 was estimated by different strategies: from tidal models, dedicated absolute gravity measurements over several days and a joint approach (including the determination of the instrumental drift) using all available absolute gravity data. The final calibration factor differs from the determination at the previous station, the transportable integrated geodetic observatory, in Concepcion, Chile, by only 0.7‰, which does not imply a significant change. From the combined approach also the mean absolute level of the SG was determined, allowing to predict absolute gravity values from the SG at any time based on a repeatability of 12nm/s2 for the FG5-227 at AGGO. Such a continuous gravity reference function provides the basis for a comparison site for absolute gravimeters in the frame of the international gravity reference frame for South America and the Caribbean. However, it requires the assessment of the total error budget of the FG5-227, including the link to the international comparisons, which will be subject of future efforts.Fil: Antokoletz, Ezequiel Darío. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Wziontek, Hartmut. Federal Agency for Cartography and Geodesy; AlemaniaFil: Tocho, Claudia. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Falk, Reinhard. Federal Agency for Cartography and Geodesy; Alemani
On the Parametrisation of Spherically-symmetric Density Models for the Earth
No full textSelbst im Rahmen eines radialsymmetrischen, nichtrotierenden, linear elastischen und isotropen Modells für die Erde kann eine unabhängige Darstellung von Dichte und elastischen Parametern, wie sie in den derzeit existierenden Referenzmodellen üblich ist, keine eindeutige Lösung liefern und führt somit zu einer Überparametrisierung. Während die elastischen Parameter durch die Laufzeiten seismischer Wellen gut verifiziert werden können, bleibt die Dichte um ein Vielfaches unbestimmter. Mit dieser Arbeit soll eine Möglichkeit zur adäquaten Beschreibung einer Normal-Dichteverteilung vorgestellt werden, die auf einer physikalisch sinnvollen, nichtempirischen Parametrisierung und einer Reduzierung auf die wesentlichen physikalischen Eigenschaften beruht. Neben dem Postulat von Homogenität der chemischen Zusammensetzung und der Phase innerhalb der einzelnen Schalen sowie adiabatischen Temperaturänderungen bildet vor allem die Annahme eines hydrostatischen Gleichgewichtszustandes, für den aus globaler Sicht kaum größere Abweichungen erwartet werden können, die Grundlage aller Betrachtungen. Unter diesen Voraussetzungen gilt die Williamson-Adams-Gleichung als fundamentaler Zusammenhang zwischen Dichte und seismischen Geschwindigkeiten. Abweichungen von den zugrundeliegenden Voraussetzungen können gegebenenfalls bei Vorliegen geeigneter Informationen a priori durch die Einführung des Bullen-Parameters in die Modellierung einfließen. Allein durch den physikalischen Zusammenhang zwischen Dichte und seismischen Geschwindigkeiten ist eine Parametrisierung der radialen Dichtefunktion noch nicht gegeben. Ausgehend von dem Postulat einer Druck-Dichte-Relation in historischen Dichtegesetzen ist es jedoch möglich, eine geeignete Funktion abzuleiten. Unter Berücksichtigung der Poisson-Gleichung für das Gravitationspotential und der Annahme hydrostatischen Gleichgewichtes ergibt sich damit eine Differentialgleichung, aus deren speziellen Lösungen in Übereinstimmung mit den seismischen Daten eine Parametrisierung der Dichte festgelegt werden kann. Ausführliche Untersuchungen zeigen, daß Funktionen für die Dichte mit ausschließlich geraden Potenzen des Radius eine bestmögliche und zugleich stabile Anpassung an die seismischen Daten bieten, während sich die derzeit gebräuchlichen allgemeinen Polynome zur Beschreibung der Dichte als weniger geeignet erweisen. Für eine stabile Bestimmung der Dichte ist weiterhin eine strenge Unterscheidung des Beitrags der einzelnen Datengruppen unabdingbar. So läßt sich aus den seismischen Geschwindigkeiten lediglich auf die Form der Dichtefunktion innerhalb der einzelnen Schalen schließen, die Festlegung des Niveaus jeder einzelnen Schale ergibt sich erst unter Hinzunahme weiterer Informationen, wie der Dichte an der Kruste-Mantel-Grenze, den geodätischen Angaben zu Gesamtmasse und Trägheitsmoment sowie aus den Frequenzen der Eigenschwingungen. Unter Berücksichtigung aller genannten Aspekte zeigt sich, daß eine eindeutige und stabile Beschreibung einer Normal-Dichteverteilung in Übereinstimmung mit seismischen und geodätischen Informationen möglich ist. Damit kann die vorgestellte Parametrisierung eine solide Grundlage für Anomaliebetrachtungen sowohl in der Geodäsie als auch in der Geophysik bilden.Even in the frame of a spherical symmetric, non-rotating, linear elastic and isotropic model an independent description of the Earth's density and elastic properties, as usual in most existing models, has no unique solution and thus leads to an over-parametrisation. Whereas the elastic properties can be verified well with the help of seismic traveltimes, the density remains much less determinate. With this work, an adequate description of a normal density distribution based on a physically meaningful, non-empirical parametrisation and an abstraction to the essential physical properties will be presented. Beside the postulate on homogeneity of the chemical composition and phase inside each shell and an adiabatic gradient of temperature, the main assumption is hydrostatic equilibrium, which must be fulfilled in a global sense for the widest parts of the Earth's interior. Under these circumstances the Williamson-Adams-equation holds as a fundamental relation between density and seismic velocities. Deviations from the underlying suppositions can be described, if necessary and appropriate information exists, a priori by the Bullen-Parameter. By the physical relation between density and seismic velocities alone a parametrisation is not given. With the help of a postulate on a pressure-density-relation in historical density laws it is possible to develop a suitable function. A differential equation follows from the Poisson equation for the inner gravitational potential in conjunction with that postulate and the assumption of hydrostatic equilibrium. Its special solutions lead in consistence with the seismic data to a parametrisation of the density. Extensive investigations show that only functions in even powers of the radius allow a best and stable fit to the seismic data, while ordinary polynomials most common in use are less eligible for a description of the density. Furthermore, to obtain a stable determination of the density a strict separation of the data-types is unavoidable. From the seismic velocities it is only possible to infer the shape of the density-function within the shells, additional data as the density below the crust-mantle-boundary, the geodetic values for mean mass and mean moment of inertia and the frequencies of the free oscillations, are necessary to fix the absolute level in each shell. Under consideration of the aforementioned aspects it is possible to obtain a unique and stable description of a normal density distribution in accordance with seismic and geodetic information. Thus the presented parametrisation can serve as a basis for anomaly analysis in geodesy and geophysics
Eterna - Programs for tidal analysis and prediction
No full textEterna, the 'Earth tide data processing package', was created by the late Prof. Hans-Georg Wenzel at the Black Forest Observatory and the University of Karlsruhe in the 1990s. This collection of programs established one standard of tidal analysis and prediction in the Earth tide community. Originally distributed only in the form of executable binaries, source code started to be distributed in the community after Hans-Georg Wenzel passed away in 1999.Access to source code is essential in order to keep the program running on new computer platforms with recent compilers. Minor (and in a few cases major) modifications where applied by researchers to correct errors or support new features. This resulted in the unpleasant situation that different versions of the programs are circulated, where the relation to the original version is unclear (in particular with respect to source code modifications) and a clear statement is missing what holders of the source are allowed to do or not. Meanwhile (20 years after Eterna was first published) technical means are commonplace to publically distribute source code together with proper licensing and with each single modification being properly documented (such that the original author must not be blamed for mistakes introduced later).In the belief that it would be in the intention of Hans-Georg Wenzel to support the continued use of Eterna in the tidal community, while allowing a clear distinction between current modifications and his original version and in the consent with his widow, Marion Wenzel, we publish the source code under terms of the GNU General Public License on a server of the Karlsruhe Institute of Technology (KIT) which is the successor of the University of Karlsruhe.We present the software as now is available in a gitlab repository, documenting all changes applied to the original code. The software is complemented by data examples, which were distributed together with the original binary executable on CD-Rom
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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