Search results for "satellite navigation"
showing 10 items of 18 documents
Locating Objects Away from Earth Surface: Positioning Accuracy
2013
The motion of the Galileo and GPS satellite constellations is simulated in Schwarzschild space-time, whereas photons travel in Minkowski space-time. This is a good enough approach to deal with the main goal of this paper: the study of positioning accuracy in the framework of the so-called relativistic positioning. Our study is based on numerical 4D simulations. In this meeting, the contribution of J.A. Morales-Lladosa contains some basic ideas which have been important to perform our numerical calculations. For four chosen emitters (satellites) of a certain constellation, many receivers located at different distances from Earth surface and in distinct directions are considered. Thus, we ver…
Iterative altitude-aiding algorithm for improved GNSS positioning
2011
The system proposed in this study relies on a WAVE P2P network, which is a proper standard to fit the vehicular environment wireless communications requests. Starting from the chance to exchange information given by this infrastructure, the possibility to improve the performance of a global navigation satellite system (GNSS) receiver based on a Kalman filter is considered. This improvement is obtained exploiting the external altitude measurements provided by other peers in the network, equipped with GNSS receivers. The topic of an altitude-aided system has been described in a previous work, that highlighted the need for a parameter that points out the effectiveness and the consistency of th…
The Uses of Analogies in Seventeenth and Eighteenth Century Science
2011
The object of this paper is to look at the extent and nature of the uses of analogy during the first century following the so-called scientific revolution.Using the research tool provided by JSTOR we systematically analyze the uses of “analog” and its cognates (analogies, analogous, etc.) in the Philosophical Transactions of the Royal Society of London for the period 1665–1780. In addition to giving the possibility of evaluating quantitatively the proportion of papers explicitly using analogies, this approach makes it possible to go beyond the maybe idiosyncratic cases of Descartes, Kepler, Galileo, and other much studied giants of the so-called Scientific Revolution. As a result a classifi…
In the Service of the Reich: Aspects of Copernicus and Galileo in Nazi Germany’s Historiographical and Political Discourse
2001
ArgumentFocus of this paper is on the historiographical fate of Nicholas Copernicus and Galileo Galilei in Nazi Germany. Both played interesting roles in Nazi propaganda and the legitimization of Nazi political goals. In the “Third Reich,” efforts to claim Copernicus as a German astronomer were closely linked to revisionist policies in Eastern Europe culminating in the war-time expansion. The example of Galileo’s condemnation by the Catholic Church in 1633 became a symbol of its unjustified opposition to new “scientific” results, namely Nazi racial theory. After Catholic opposition against Nazi racial theory had reached a peak in 1937, the Galileo affair was turned into an instrument of Naz…
Relativistic positioning: errors due to uncertainties in the satellite world lines
2014
Global navigation satellite systems use appropriate satellite constellations to get the coordinates of an user -close to Earth- in an almost inertial reference system. We have simulated both GPS and GALILEO constellations. Uncertainties in the satellite world lines lead to dominant positioning errors. In this paper, a detailed analysis of these errors is developed inside a great region surrounding Earth. This analysis is performed in the framework of the so-called relativistic positioning systems. Our study is based on the Jacobian, J, of the transformation giving the emission coordinates in terms of the inertial ones. Around points of vanishing J, positioning errors are too large. We show …
Artificial organisms as tools for the development of psychological theory: Tolman's lesson
2007
In the 1930s and 1940s, Edward Tolman developed a psychological theory of spatial orientation in rats and humans. He expressed his theory as an automaton (the ‘‘schematic sowbug’’) or what today we would call an ‘‘artificial organism.’’ With the technology of the day, he could not implement his model. Nonetheless, he used it to develop empirical predictions which tested with animals in the laboratory. This way of proceeding was in line with scientific practice dating back to Galileo. The way psychologists use artificial organisms in their work today breaks with this tradition. Modern ‘‘artificial organisms’’ are constructed a posteriori, working from experimental or ethological observations…
The Kalman Filter and Its Applications in GNSS and INS
2011
This chapter contains sections titled: Introduction Review of Kalman Filtering and Extended Kalman Filtering for Navigation EKF-Based PVT Computation in a Stand-Alone GNSS Receiver Inertial Navigation Fundamentals IMU Alignment General Architecture for the Loose Integration General Architecture for the Tight Integration General Architecture for the Ultra-Tight Integration Conclusions References Appendix A
SAPERE ECONOMICO E METODO SCIENTIFICO NELL’ILLUMINISMO LOMBARDO: NOTE DA “IL CAFFÈ”
2011
Economic knowledge and scientific method in the lombard enlightenment. Notes from «Il caffè». The connections, emerging between the 16th and the 18th century, between the evolution of economic knowledge and the rise of the scientific method, are important research topics for historians of economic ideas. However, further research on the application of the scientific method is still needed, especially when we come to the analysis of how economic principles took shape in Lombardy during the Enlightenment. The same need for further research concerns the debates on economic policy during the Age of Reforms in the latter half of the eighteenth century. This is even more necessary for Milanese En…
Sachs-Wolfe at second order: the CMB bispectrum on large angular scales
2009
We calculate the Cosmic Microwave Background anisotropy bispectrum on large angular scales in the absence of primordial non-Gaussianities, assuming exact matter dominance and extending at second order the classic Sachs-Wolfe result delta T/T = Phi/3. The calculation is done in Poisson gauge. Besides intrinsic contributions calculated at last scattering, one must consider integrated effects. These are associated to lensing, and to the time dependence of the potentials (Rees-Sciama) and of the vector and tensor components of the metric generated at second order. The bispectrum is explicitly computed in the flat-sky approximation. It scales as l(-4) in the scale invariant limit and the shape d…
Space-borne frequency comb metrology
2016
Precision time references in space are of major importance to satellite-based fundamental science, global satellite navigation, earth observation, and satellite formation flying. Here we report on the operation of a compact, rugged, and automated optical frequency comb setup on a sounding rocket in space under microgravity. The experiment compared two clocks, one based on the optical D2 transition in Rb, and another on hyperfine splitting in Cs. This represents the first frequency comb based optical clock operation in space, which is an important milestone for future satellite-based precision metrology. Based on the approach demonstrated here, future space-based precision metrology can be i…