Texte remanié de: Th. Doct.-Ing., 1985--Paris VI.

Th. doct.-ing.--Inform.--Nancy--I.N.P.L., 1980.

Part one of the thesis contains analysis of the methods of computation in navigation. We start with loxodromic navigation and, although this subject is well documented, we make a positive attempt to analyse the subject matter using the methods of differential geometry. We then turn to the problem of shortest path curves and set out an alternative method of solving the problem of navigating along the arc of a great circle on the surface of a sphere which can be generalised to other surfaces. In particular, a contribution made by the thesis is an analysis of the problem of navigating along shortest path geodesic arcs on the surface of a spheroid which introduces an algebraic representation of the geodesic curve by solving Clairaut' s equation using a cylindrical transformation. We are therefore able to compute the the coordinates of the positions of points along the path of the geodesic and the length of arc along the path of the. geodesic curve can then be computed step by step between these points by a numerical method - the Direct Cubic Spline method which was first introduced by this author in the Bachelor of Philosophy thesis in 1982 and is developed further in part 2 of this thesis. We apply this method also to the special problem of computing the distance along the shortest path between nearly antipodean points on the surface of a spheroid. We analyse the problem of computing an observer's position on the surface of the Earth using astronomical observations and show how a position locus is distorted when it is transferred over the surface. We offer a method of computing the observer's position by a series of observations of a single astronomical body taken over a comparitively short period of time and which does not necessarily include an observation at the tide of meridian passage of the body. In part two of the thesis we discuss the Direct Spline approximation to integrals and give some error bounds. The Direct Cubic Spline is a step by step method of fitting a cubic spline to the integral of a function directly which computes the value of the integral of the function step by step between the data points which need not be evenly spaced. We extend the idea to splines of higher order and give the formula from which they may be obtained but we show that, except for a particular special form of the direct quartic spline. the higher order direct splines do not yield algorithm for computing integrals which are as efficient as the Direct Cubic Spline.

Heading measurement is required on board light aircraft, surface ships and underwater vessels. It is also used for the position navigation of commercial cars and military vehicles.

Radio waves in the Very Low Frequency (VLF) band (3-30kHz) are reflected from the lowest part of the ionosphere, the D-region. Due to their relative stability and low attenuation they are utilized for navigation, timing and frequency comparisons. Any changes in D-region electron density structure are known to influence the phase velocity of VLF waves. Both regular diurnal and irregular behaviour have been extensively reported. A comparison of theoretical techniques is presented, demonstrating the influence of changes in radio frequency, ground conductivity, geomagnetic path azimuth and latitude. Described in this thesis is an analysis of the experimentally determined performance, within the U.K., of the VLF navigation system 'Omega'. The system relies on the stability of the phase velocity of the transmitted signals to provide a navigation fix. Both diurnal and seasonal variations in signal phase are investigated while the effects of modal interference and ionospheric disturbances are noted. In order to reduce errors resulting from regular variations in phase velocity, a prediction technique has been developed by the Omega Navigation System Operations Detail (ONSOD). An assessement of the validity of ONSOD predictions within the U.K. is presented and it is apparent that a number of differences exist between them and the experimental data. Major errors are evident at dawn over certain near north-south paths and marked differences may occur between data collected at particular sites. The relevance of these differences to Differential Omega is noted and an investigation into the performance of an Omega/Satellite combined system is conducted. The variations within the U.K. are not completly accounted for by changes in propagation path length although theoretical investigations indicate the importance of changes in electron density structure along the whole path. It is evident that the sunrise schedules of the ONSOD prediction program require modification.

No description available.

Th. doct.--Histoire des sciences et des techniques--Université de Nantes, 2001.

This creative project has taken the form of a 16 millimeter color documentary film that analyzed the proposed alteration of a major natural resource in Indiana; i.e., the Wabash River. The agency responsible for studying the proposed alteration was the U.S. Army, Corps of Engineers, which was acting in response to Congressional authorization.The film analyzed the proposed alteration, known as Wabash Navigation, from the perspectives of history, ecology, economics, and philosophy; differing world views inherent in the global ecological crisis were found to exist in the values of waterway advocates and opponents.The Corps of Engineers found this particular project to be non-feasible. However, the historical and philosophical point is made that non-feasibility does not mean that efforts to promote the waterway would necessarily be dropped. Viewers are asked to analyze the issue from the various perspectives represented in the film and formulate their own opinions.

Thesis (Ph. D.)--Ohio University, November, 1988. / Title from PDF t.p.

No description available.