The impact of navigation satellite ephemeris error on common-view time transfer

Author(s):  
Hongwei Sun ◽  
Haibo Yuan ◽  
Hong Zhang
1989 ◽  
Vol 16 ◽  
pp. 341-362 ◽  
Author(s):  
Jan Vansina

Around 1850 the peoples of central Africa from Duala to the Kunene River and from the Atlantic to the Great Lakes shared a common view of the universe and a common political ideology. This included assumptions about roles, statuses, symbols, values, and indeed the very notion of legitimate authority. Among the plethora of symbols connected with these views were the leopard or the lion, the sun, the anvil, and the drum, symbolizing respectively the leader as predator, protector, forger of society, and the voice of all. Obviously, in each case the common political ideology was expressed in slightly different views, reflecting the impact of differential historical processes on different peoples. But the common core persisted. The gigantic extent of this phenomenon, encompassing an area equal to two-thirds of the continental United States, baffles the mind. How did it come about? Such a common tradition certainly did not arise independently in each of the hundreds of political communities that existed then. However absorbent and stable this mental political constellation was, it must have taken shape over a profound time depth. How and as a result of what did this happen? Is it even possible to answer such queries in a part of the world that did not generate written records until a few centuries ago or less?This paper addresses this question: how can one trace the social construction of such a common constellation over great time depths and over great regional scale? All the peoples involved are agriculturalists and the political repertory with which we are concerned could not easily exist in its known form outside sedentary societies.


2000 ◽  
Vol 53 (2) ◽  
pp. 261-271 ◽  
Author(s):  
D. Brocklebank ◽  
J. Spiller ◽  
T. Tapsell

This, and the following three papers, where first presented at GNSS 99, the Second European Symposium on Global Navigation Satellite Systems held in Genoa, Italy from 5th to 8th October 1999.Galileo is being developed as the European contribution to the next generation of navigation satellites to replace GNSS1. Sponsored by the European Union, Galileo will be a civil, internationally controlled and operated system that will secure the long-term availability of satellite-based navigation services for multi-modal purposes throughout the European region and beyond. Galileo will be designed to support a wide variety of applications. These include professional navigation, position reference, safety, emergency, tracking, sport/leisure and governmental. Such services may be open to all, for safety-of-life applications, or for commercial users. In the case of safety and commercial applications in particular, it is imperative that the appropriate institutional control and regulatory framework is in place for purposes of safety and economic regulation. To ensure that the various parties understand their obligations and liabilities, clear legal instruments must be put in place to support the organisational framework. It is planned to attract private investment to fund elements of system development and operation through Private/Public Partnership arrangements. At present there is no institutional, regulatory or legal framework that will enable the early impetus to Galileo development to be maintained. This presents a challenge that Europe must address without delay. It has been the subject of several European Commission studies in the past twelve months. In a complementary activity under contract to the European Space Agency (ESA), a European industry consortium comprising Alcatel, Alenia, DASA and Matra Marconi Space was tasked to complete the preliminary design of the space and ground segments by the Autumn of 1999. One task of this study, led by Matra Marconi Space, relates to a study of the impact of institutional, regulatory and legal issues on the organisation and development of Galileo. This paper describes the studies undertaken into these issues within the overall Galileo development programme.


Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3646 ◽  
Author(s):  
Mariusz Specht ◽  
Cezary Specht ◽  
Andrzej Wilk ◽  
Władysław Koc ◽  
Leszek Smolarek ◽  
...  

Mobile Global Navigation Satellite System (GNSS) measurements carried out on the railway consist of using satellite navigation systems to determine the track geometry of a moving railway vehicle on a given route. Their purposes include diagnostics, stocktaking, and design work in railways. The greatest advantage of this method is the ability to perform measurements in a unified and coherent spatial reference system, which effectively enables the combining of design and construction works, as well as their implementation by engineering teams of diverse specialties. In the article, we attempted to assess the impact of using three types of work mode for a GNSS geodetic network [Global Positioning System (GPS), GPS/Global Navigation Satellite System (GLONASS) and GPS/GLONASS/Galileo] on positioning availability at three accuracy levels: 1 cm, 3 cm and 10 cm. This paper presents a mathematical model that enables the calculation of positioning availability at these levels. This model was also applied to the results of the measurement campaign performed by five GNSS geodetic receivers, made by a leading company in the field. Measurements with simultaneous position recording and accuracy assessment were taken separately on the same route for three types of receiver settings: GPS, GPS/GLONASS and GPS/GLONASS/Galileo in an urban area typical of a medium-sized city. The study has shown that applying a two-system solution (GPS/GLONASS) considerably increases the availability of high-precision coordinates compared to a single-system solution (GPS), whereas the measurements with three systems (GPS/GLONASS/Galileo) negligibly increase the availability compared to a two-system solution (GPS/GLONASS).


2020 ◽  
Vol 25 ◽  
Author(s):  
N. Daniels ◽  
C. Cosma ◽  
A. Llewellyn ◽  
D. Banks ◽  
H. Morris ◽  
...  

Abstract Smoking was one of the biggest preventable killers of the 20th century, and it continues to cause the death of millions across the globe. The rapid growth of the e-cigarette market in the last 10 years and the claims that it is a safer form of smoking, and can help with smoking cessation, have led to questions being raised on their possible impact to society, the health of the population and the insurance industry. Recent media attention around the possible health implications of e-cigarette use has also ensured that this topic remains in the public eye. The e-cigarette working party was initiated by the Institute and Faculty of Actuaries’ Health and Care Research Sub-Committee in July 2016, with the primary objective of understanding the impact of e-cigarettes on life and health insurance. In this paper, we have looked at all areas of e-cigarette usage and how it relates to insurance in the UK market. In particular, we have covered the potential risks and benefits of switching to e-cigarettes, the results of studies that have been published, the potential impact on underwriting and claims processes and the potential impact on pricing (based on what modelling is possible with the data available). Research in this area is still in its infancy and data are not yet mature, which makes predicting the long-term impact of e-cigarette smoking extremely challenging, for example, there are no studies that directly measure the mortality or morbidity impact of long-term e-cigarette use and so we have had to consider studies that consider more immediate health impacts or look more simply at the constituents of the output of an e-cigarette and compare them to that of a cigarette. The data issue is further compounded by the findings of studies and the advice of national health authorities often being conflicting. For example, while National Health Service England has publicly stated that it supports the growth of e-cigarette usage as an aid to reduce traditional smoking behaviour, the US Food and Drug Administration has been much more vocal in highlighting the perceived dangers of this new form of smoking. Users’ behaviour also adds complexity, as dual use (using both e-cigarettes and cigarettes) is seen in a high percentage of users and relapse rates back to cigarette smoking are currently unknown. Having talked to a number of experts in the field, we have discovered that there is certainly not a common view on risk. We have heard from experts who have significant concerns but also to experts who do believe that e-cigarettes are far safer than tobacco. We have purposefully considered conflicting evidence and have consulted with various parties so we can present differing points of view, thereby ensuring a balanced, unbiased and fair picture of our findings is presented. The evidence we have reviewed does suggest that e-cigarettes are a safer alternative to traditional smoking, but not as safe as non-smoking. There are no large, peer-reviewed, long-term studies yet available to understand the true impact of a switch to e-cigarette use, so currently we are unable to say where on the risk spectrum between cigarette smoking and life-time non-smoking it lies. We do not yet understand if the benefits seen in the studies completed so far will reduce the risk in the long term or whether other health risks will come to light following more prolonged use and study. This, coupled with concerns with the high proportion of dual use of cigarettes and e-cigarettes, relapse rates and the recent growth in medical problems linked with e-cigarette use, means that we need to wait for experience to emerge fully before firm conclusions can be drawn. Although we have presented a view, it is vitally important that our industry continues to monitor developments in this area and fully considers what next steps and future actions may be required to ensure our position reflects the potential benefits and risks that e-cigarette use may bring. We feel that the time is right for a body such as the IFoA to analyse the feasibility of collecting the necessary data through the Continuous Mortality Investigation that would allow us to better analyse the experience that is emerging.


2007 ◽  
Vol 50 (4) ◽  
pp. 452-489 ◽  
Author(s):  
Corinne Lefèvre

AbstractThis article argues against the common view according to which the Mughal emperor Jahāngīr was a political lightweight who was dominated by his famous spouse Nūr Jahān. Beginning with a discussion of the historiographical processes which presided over the construction of such a negative image, the essay continues with a thorough re-examination of the emperor's memoirs entitled Jahāngīr Nāma. This text brings out a coherent and original political voice, in which Jahāngīr skilfully connects his identities of sovereign, naturalist, and collector. The conclusion evaluates the impact of this discourse through a brief analysis of the reaction of the Mughal political and religious elite. Cet article s'élève contre l'opinion commune suivant laquelle l'empereur moghol Jahāngīr fut une figure politique mineure, dominée par sa célèbre épouse Nār Jahīn. Il s'ouvre sur une discussion des processus historiographiques qui présidèrent à la construction de cette image négative, et se poursuit par une réexamen serré des mémoires de l'empereur (ou Jahāngīr Nāma). En ressort une voix politique cohérente et originale, Jahāngīr articulant habilement ses identités de souverain, de naturaliste et de collectionneur. La conclusion évalue l'impact de ce discours à travers un rapide analyse de la réaction qu'il suscita auprès de l'élite politique et religieuse du royaume.


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