Dans le cadre d’un projet d’aménagement, la reconnaissance du sous-sol est une étape prépondérante pour la construction d’un bâtiment. Le géotechnicien se doit de définir le comportement mécanique des sols à partir d’un nombre limité de sondages. La problématique soulevée par les prospections géotechniques est qu’il est difficile d’une part d’étendre une information ponctuelle dans l’environnement proche des sondages, et d’autre part d’estimer la variabilité latérale des matériaux. Dans cette optique, cette thèse développe une approche novatrice de combinaison de méthodes géophysiques aidant à la quantification de la variabilité spatiale des structures géoélectriques du sous-sol. Dans un second temps, au regard des limites rencontrées dans la modélisation 3D des structures géoélectriques du sous-sol, nous avons mis au point un processus innovant de modélisation 3D des propriétés physiques du sous-sol par combinaison de méthodes géophysiques. Les travaux menés ont permis de caractériser les paramètres régissant le positionnement et la quantité de données sources nécessaires.Enfin, un dispositif innovant de mesure de Tomographie de Résistivité Electrique en Cinématique (TREC) a été développé. La validation du dispositif sur trois sites différents a permis de mettre en évidence sa capacité à détecter les structures géoélectriques des sols sur un linéaire de plusieurs centaines de mètres. Ce dispositif constitue un outil précieux pour l’étude des structures géoélectriques du sous-sol dans le cadre de prospections géophysiques à grand rendement. / The geotechnical study of a building project is a decisive step for the construction of it. The geotechnical engineer must define the mechanical behavior of soils from a limited number of drills. The problem of the geotechnical surveys is, on the one hand that difficult to extend a punctual data in the near space to the drills,and on the other hand to estimate the lateral variability of materials. In this context, this thesis develops an innovative approach by combination of geophysical methods to quantify the spatial variability of geoelectrical structures. In asecond time, against the known limits of the 3D modeling of soil geoelectrical structures, we have developed an innovative process of 3D modeling of the physical properties of soil by geophysical methods combination. These works allow characterizing the parameters who governing the positioning and the number of necessary primary data.Finally, an innovative measuring device of Kinematic Electrical Resistivity Tomography (KERT) has been developed. The validation of the device on three different site has allowed to highlight its ability to detect the soil geoelectrical structures within a linear of hundreds meters. This device is a valuable tool for studying soil geoelectrical structures in the context of high yield geophysical prospection.

In this thesis, parameterizations of non-linear interactions in quasigeostrophic (QG) flows for severely truncated models (STM) and Large Eddy Simulations (LES) are studied. Firstly, using Direct Numerical Simulations (DNS), atmospheric barotropic flows over topography are examined, and it is established that such flows exhibit multiple equilibrium states for a wide range of parameters. A STM is then constructed, consisting of the large scale zonal flow and a topographic mode. It is shown that, qualitatively, this system behaves similarly to the DNS as far as the interaction between the zonal flow and topography is concerned, and, in particular, exhibits multiple equilibrium states. By fitting the analytical form of the topographic stationary wave amplitude, obtained from the STM, to the results obtained from DNS, renormalized dissipation and rotation parameters are obtained. The usage of renormalized parameters in the STM results in better quantitative agreement with the DNS.¶ In the second type of problem, subgrid-scale parameterizations in LES are investigated with both atmospheric and oceanic parameters. This is in the context of two-level QG flows on the sphere, mostly, but not exclusively, employing a spherical harmonic triangular truncation at wavenumber 63 (T63) or higher. The methodology that is used is spectral, and is motivated by the stochastic representation of statistical closure theory, with the ‘damping’ and forcing covariance, representing backscatter, determined from the statistics of DNS. The damping and forcing covariance are formulated as 2 × 2 matrices for each wavenumber. As well as the transient subgrid tendency, the mean subgrid tendency is needed in the LES when the energy injection region is unresolved; this is also calculated from the statistics of the DNS. For comparison, a deterministic parameterization scheme consisting of 2×2 ‘damping’ parameters, which are calculated from the statistics of DNS, has been constructed. The main difference between atmospheric and oceanic flows, in this thesis, is that the atmospheric LES completely resolves the deformation scale, the energy and enstrophy injection region, and the truncation scale is spectrally distant from it, being well in the enstrophy cascade inertial range. In oceanic flows, however, the truncation scale is in the vicinity of the injection scale, at least for the parameters chosen, and is therefore not in an inertial range. A lower resolution oceanic LES at T15 is also examined, in which case the injection region is not resolved at all.¶ For atmospheric flows, it is found that, at T63, the matrix parameters are practically diagonal so that stratified atmospheric flows at these resolutions may be treated as uncoupled layers as far as subgrid-scale parameterizations are concerned. It is also found that the damping parameters are relatively independent of the (vertical) level, but the backscatter parameters are proportional to the subgrid flux in a given level. The stochastic and deterministic parameterization schemes give comparably good results relative to the DNS. For oceanic flows, it is found that the full matrix structure of the parameters must be used. Furthermore, it is found that there is a strong injection of barotropic energy from the subgrid scales, due to the unresolved, or partially resolved, baroclinic instability injection scales. It is found that the deterministic parameterization is too numerically unstable to be of use in the LES, and instead the stochastic parameterization must be used to obtain good agreement with the DNS. The subgrid tendency of the ensemble mean flow is also needed in some problems, and is found to reduce the available potential energy of the flow.

The aim of this thesis has been to investigate the benefits, pitfalls and possibilities of using geophysical methods in archaeological projects. This is exemplified by surveys carried out at archaeological sites in different geographical and chronological contexts. The thesis also aims at investigating the cause for the under-use of the methods in Swedish archaeology by looking at previously conducted surveys. The methods used during these surveys have been Ground-penetrating radar (GPR), magnetometer, slingram and a kappameter. The surveys in the mountain tundra region of Lapland show that magnetic susceptibility surveys is a valuable aid in discovering heaps of fire-cracked stones and when combined with magnetometry, also hearths. GPR and magnetometer surveys within the Migration Period ringfort Sandbyborg provided the spatial layout of the fort and indicated, along with results from recent excavations and metal detections, many similarities with the ringfort Eketorp II. The non-magnetic character of the sedimentary bedrock on Öland and Gotland is suitable for magnetometer surveys and the method is also highly appropriate for the detection of the remains of high-temperature crafts. GPR surveys at St. Mary’s Dominican convent in Sigtuna produced the spatial layout of the central cloister area. The investigations also show that the geology, pedology, land use and the character of commonly occurring prehistoric remains in Sweden, in certain circumstances and in certain areas, have restricted the possibility of successfully carrying out geophysical surveys. Care must therefore be taken to choose the right instrument for the survey and to tailor the sampling density of each geophysical survey, according to the character and size of the expected archaeological remains, in order to maximize their information return. To increase the use of geophysical methods in Sweden the educational opportunities, both for surveyors and professional archaeologists, need to improve. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript.</p>

Inertial navigation systems (INSs) have the well-known advantages of being self-contained, weatherproof, jam-proof, and non-self-revealing while providing stable navigation information with little high-frequency noise. However, their single most important drawback is the growth of their error cumulatively with time in an unbounded manner. Navigation systems based on position fixing, in contrast, offer bounded errors in the long term, but their output is usually contaminated with strong high-frequency noise. To harness the advantages of both types of systems, INSs have been traditionally aided or augmented by one or more fixing system(s). Such an arrangement preserves the excellent short-term stability and damping (i.e. high-frequency rejection) capability of INSs while limiting its long-term drift. In recent years, the availability of navigation information from the Global Positioning System (GPS) reliably and accurately over the entire globe has made it a natural choice as the means of augmentation of INSs. An integrated navigation system combining data from two or more ‘pure’systems is called a hybrid navigation system (HNS). There is no unique way of combining navigation information from the INS and GPS. Depending on the goals and specifications of the overall navigation system, the instrument and equipment available, cost constraints, and technology options, the scheme for integrating INS and GPS may take one of many forms. In generic terms integration of diverse ‘pure’ navigation systems can be performed at various levels. At the simplest and most basic level, each system may be allowed to run independently, generating its own navigation data separately which may then be combined periodically to reset any accumulated error. At the other extreme, the two (or more) systems may be intimately coupled right at their raw data levels in a quasi-continuous manner with the intention of maximising their mutually beneficial effect and deriving the ‘best’ possible navigation information. Hybrid navigation architectures have been a subject of much research and development, and a significant body of information is available on the subject. However, there are clear gaps in open literature on many practical issues that arise in the context of implementing specific HNSs. In this thesis we investigate the architecture, implementation and performance issues of HNSs that combine stand-alone INS and GPS units. The thesis consists of eight chapters. The first chapter offers an introduction to the navigation problem and discusses the basic types of navigation including inertial and satellite navigation. Inertial sensors such as gyroscopes and accelerometers and the GPS are discussed in some detail. The types and principle of gyroscopes and accelerometers and the error sources in inertial navigation are briefly covered, as also the advantages and disadvantages of INS and the trends in inertial system development.The chapter also touches upon GPS segments (space, control and user), the theory and determination of position fix, and the GPS error sources. Mention is also made of the types of GPS receiver available and the trends in GPS technologies. Integration of INS and GPS and its benefits are discussed and a set of specifications for an integrated system is laid out to serve as the basis for the configurations proposed later. The second chapter, in its three sections, provides a summary of the significant literature relevant to INS and GPS in the context of their integration. Chapter three discusses mechanisation aspects of the INS-GPS hybrid navigation system. This chapter is divided into three sections. In the first section the frames of reference, INS mechanisation and the error equations are discussed. The definitions for the various frames such as body, platform, local level, geodetic, Earth-centred-Earth-fixed (ECEF), and the computer frame are mentioned along with the direction cosine matrices for the transformation of frames. In the second section various types of mechanisation of INS and the summary of tilt, velocity and position equations are described. The INS can be mechanised in two ways: the stable platform and the strap-down. In this chapter the general error equations for platform tilt, velocity and position are listed. Platform-based systems can be mechanized as one of the following types, viz. unipolar, Focualt, north pointing and wander azimuth. The definitions and summary of the tilt, velocity and position, and the error equations are given for all these types of mechanization. The accelerometer and gyro error models are discussed. It is pointed out that inclusion of all the possible INS states in the model would lead to a 45-state system which would be too complex to handle on board. The scope for reduction of model order and the effect of such reduction are brought out. The section ends with a summary of the INS error equations considered for implementation. In the third section the GPS principle and derivation of navigation solutions based on GPS measurements are dealt with. GPS error modelling, computation of DOP (dilution of precision), and clock modelling are also discussed. In this section the navigation solution for various classes of users – stationary, low-dynamics, medium-dynamics and high-dynamics – are discussed. The INS model and the clock model defined in this chapter are used in configuring the integrated system model later. Chapter four discusses the various HNS configurations and their implementation to mitigate the INS error. Three levels of integration are considered: a. Output coupled: The INS needs initial alignment during which the INS position and velocity are initialised with the precisely known co-ordinates and components at the starting location. Starting with these initial conditions, the INS-sensed accelerations are continuously integrated to yield the current velocity and position. As mentioned earlier, the INS error is dependent on this initial value and further increases with time. If the initial position and velocity inputs are precise, the short-term INS accuracy (typically for the first 10-15 minutes in case of aircraft) is usually within acceptable limits. Further error built up during longer flights can be reduced by periodic updation of INS with the precise position and/or velocity values. To achieve this the pilot may, for example, fly over waypoints whose co-ordinates are precisely known. This would constitute a physical or manual method of INS re-initialisation. A better and more modern method is to use precise GPS-derived information to reinitialise the INS periodically and automatically. b. Medium coupled: Another way of mitigating the INS error build-up is by using medium-coupled HNS wherein the INS errors are estimated using the GPS measurements as reference. The INS outputs are corrected by applying these error estimates. The important point to note here is that in medium coupling, the errors in the INS states are considered instead of the states themselves. The final geodetic outputs from the two systems are used as measurements. A twelve-state indirect feed-forward Kalman filter is used to estimate the INS position error. c. Tightly coupled: The basic measurements from the GPS are pseudoranges which are the distances from the user to the GPS satellites. By making a minimum of four such measurements the GPS receiver computes the user location in the geodetic coordinates. Conversely, knowing the user position from INS, it is possible to calculate the expected pseudoranges to known GPS satellite locations. Comparing the measured and the computed pseudoranges, the filter estimates the errors in the INS position. In this work a seventeen-state, feed-forward, indirect Kalman filter is configured to estimate the INS-derived pseudorange errors. These errors are then translated into positional errors which are used to correct the indicated INS positions. In configuring the filter it is assumed that the INS and GPS are physically separated and data transfer is through the interface buses. In this chapter the simulators used for validation and performance estimation of the configurations are also described. Two simulators are used to validate the hybrid system, namely, software-and hardware-based simulators. The simulators simulate the six-degree-of-freedom of trajectory generator, and error models of INS and GPS. The truth data from the trajectory generator are combined with the INS error and GPS error to get the INS and GPS outputs respectively. The fifth and sixth chapters covers the validation of the above-mentioned three configurations. Since analysis of output coupled systems is rather straightforward, simulation and validation of the configuration are carried out for the medium and tightly coupled systems Covariance analysis and Error analysis modes of simulation are carried out to study and validate the behaviour of the configurations. In covariance analysis one obtains the root mean square (rms) value of the errors obtained from several Monte Carlo runs. It gives an estimate of the lower bound of the system errors. Covariance simulation provides a degree of confidence in the error model but is generally not sufficient to expose the complete behaviour of the system. For detailed investigation, error simulation needs to be carried out for the entire navigation system. In the thesis, covariance simulation is carried out for both the configurations to check the sensitivity of the system to measurement update rates, process noise, update times for the transition matrix, and also for the validity of the truncation of the Taylor series expansion. The details of the simulation processes and their results are discussed in these chapter. The seventh chapter makes a performance comparison of the configurations and draws inferences for practical hybrid system implementation. From the comparisons it is seen that the loosely coupled configuration is the simplest. In this configuration there is no requirement of the Kalman filter. The accuracy depends on the update rate. If the position update is made, for example, once every 600 s then the error in the combined system will be limited to the sum of the error due to the GPS and that accumulated in the INS alone over the of 600 s interval. There is no coordinate transformation required. In the case of medium coupled filter the addition of process noise to the GPS clock model is not critical. The position accuracy achieved is around 2 m (rms). The coordinate transformations are only from the body to platform, and platform to geodetic axes. The observation matrix is very simple in this case and the computation burden is low. Dynamic tuning of the measurement matrix is not required in real time.In the case of tightly coupled configuration the addition of a certain amount of process noise deliberately to the GPS clock model is critical. The position accuracy achieved with tight coupling is around found to be 34 m (rms) without the addition of process noise. On addition of a controlled amount of noise to the GPS clock bias and clock drift states and inclusion of measurement noise as a function of GPS signal strength, the position accuracy improves significantly, to about 7m (rms). Figures 2a and 2b below depict the behaviour before and after inclusion of the noise. The coordinate transformations are from body to platform, platform to geodetic, and geodetic to ECEF coordinates, and vice versa. The observation matrix (H) for this integration model is very complicated, and the computational burden is very high. In this configuration H transfers the measurements from metres to radians. Dynamic tuning of measurement matrix is required in this case. Chapter eight of the thesis summarises the results and lists out the conclusions arrived at from the study. It also includes a section with suggestions for future work in this direction.

Archaeogeophysics, the use of eophysical mapping techniques to recover archaeological information, is being used with increasing success in North America. Archaeologists can often use geophysics as a tool for collecting data suitable for direct archaeological interpretation (Kvamme 2003). In some cases, geophysics can be used to map entire archaeological landscapes providing an image of the site that is not easily achievable through the use of traditional archaeological excavations. This dissertation uses archaeogeophysical data from three prehistoric sites to gain insights into their layout and community organization as well as explore the possibilities and potentials of using broad scale geophysical surveys in North American archaeological research. / text

Studies of geologic and geophysical data from the offshore of India have revealed two geologically distinct areas with inferred gas hydrate occurrences: the passive continental margins of the Indian Peninsula and along the Andaman convergent margin. The Indian National Gas Hydrate Program (NGHP) Expedition 01 was designed to study the occurrence of gas hydrate off the Indian Peninsula and along the Andaman convergent margin with special emphasis on understanding the geologic and geochemical controls on the occurrence of gas hydrate in these two diverse settings. NGHP Expedition 01 established the presence of gas hydrates in Krishna- Godavari, Mahanadi and Andaman basins. The expedition discovered one of the richest gas hydrate accumulations yet documented (Site 10 in the Krishna-Godavari Basin), documented the thickest and deepest gas hydrate stability zone yet known (Site 17 in Andaman Sea), and established the existence of a fully-developed gas hydrate system in the Mahanadi Basin (Site 19).

To understand the mechanisms of energy exchange between the tropics and the midlatitudes, it is necessary to develop simplified climate models. Motivated by linear wave theory, one such model is derived below. It captures the nonlinear interaction between barotropic and first baroclinic modes. In particular, it allows for the study of the barotropic response to a baroclinic forcing. Numerical methods for handling this nonlinear system are carefully developed and validated. The response generated by a physically realistic Kelvin wave forcing is studied and is found to consist mainly of one eastward propagating wave (phase-locked to the forcing) and two westward propagating (Rossby) waves. The Rossby waves are shown to be highly constrained by the initial parameters of the forcing and an explanation of this result is proposed.

The thesis investigates the concepts of archaeological spatial association within the context of both site and regional data sets. The techniques of geophysical surveying, surface distribution collection and aerial photography are described and discussed. Several new developments of technique are presented as well as a detailed discussion of the problems of data presentation and analysis. The quantitative relationships between these data sets are explored by modelling them as operands and describing association in terms of operators. Both local and global measures of association are considered with a discussion as to their relative merits. Methods for the spatial association of regional lattice and point processes are developed. A detailed discussion of distance based spatial analysis techniques is presented.

The Comet Gold Mine is in the Murchison mineral field which lies within the Yilgarn Craton of Western Australia. Several different geophysical methods were used in this study to define the geophysical signatures of sedimentary iron formations (SIF) and altered basalt associated with gold mineralisation. The geophysical surveys carried out at the Comet Gold Mine were gravity, sub-audio magnetics (SAM), transient electromagnetics (TEM) and downhole geophysical logging. Data from previous geophysical surveying were also used, and these included highresolution aeromagnetics and TEMPEST airborne electromagnetics. Other exploration information, such as geology and drillhole data, were integrated with geophysical results to study the geophysical responses and generate a geophysical interpretation map. / The main aim of this study was to generate an understanding of the various geophysical responses of geology and gold mineralisation in the Comet Mine area for future gold exploration in this region. Particularly, the study focused on the ability of the SAM method to map out geology and geophysical response for gold mineralisation. The response from SAM surveying has been investigated over an area of 13 sq kms. The SAM surveying was completed using a transmitter current of 5-8 Amp with a 50% duty cycle at 4 Hz frequency, which was considered the best setting for the Comet area. The SAM anomalies were compared to results from other geophysical methods. The results of all geophysical surveying suggested that the TEM method was also effective for identifying altered sulphide and magnetic altered rock associated with gold mineralisation. / Experiments were carried out using SAM surveying with electrodes in standard surface pits and pits placed directly into the gold mineralised structure. Both surveys showed very similar results, so in this area, surface electrode pits work well for current injection during SAM surveys. The similarities are probably due to the lack of conductive regolith cover in the Comet Mine area. / The SAM response was studied for survey grids using different electrode positions and directions. Experiments in changing SAM electrode position over the same area were carried out along and across geological strike to detect the different geological structure directions. The EQMMR response was different for electrodes oriented at 90º when surveys were repeated over the same area. SAM mainly measures conductive features running sub-parallel to the electrode direction, but the EQMMIP response was mostly the same, despite the difference in electrode direction. In addition, the EQMMIP result was very similar for rotated grids, with some distortion occurring around the main EQMMR anomaly near the Venus open cut pit. Therefore, SAM chargeability was not strongly polarised along the electrode direction like the EQMMR response. This is consistent with the theory of MIP that the method detects the effect of induced polarisation in the earth by virtue of the magnetic fields associated with current flow in polarisable bodies within the earth. / Gravity data were collected along in 4 transects 500 m apart and at 50 m station spacing. 3D gravity modelling using polygonal shapes was completed to a good fit with felsic and mafic rocks by having rock units dip to the SE. Euler depth solution calculations were applied to locate contacts and deep gravity sources. Gravity surveying has also proved to be a useful survey method for geological mapping and locating regional structures. / Ground TEM survey data were used at the Venus prospect to map out conductive zones at depths ranging from 30 to 90 m. All anomaly bodies were interpreted to have a SE dip. The modelled ground TEM results were compared to TEMPEST airborne electromagnetic conductivity depth slices. Both EM survey results showed reasonably similar patterns, but the ground TEM method provided more reliable conductor locations and depth estimations that correlated well with the drilling information and downhole conductivity logging. / Geophysical logs of natural gamma and inductive conductivity were surveyed in 5 drillholes that intersected gold alteration zones. The alteration zones associated with gold mineralised sediments, sulphide and magnetic minerals were identified in the downhole logs as increased conductivity, with a sight increase in the natural gamma response. Natural gamma was usually high above a background of host rock in the gold mineralised shear zones. This was likely due to K associated with the clay rich SIF units, and sericite and biotite from gold related alteration. During this study, drillhole CTRC028 was drilled into a modelled TEM anomaly, and gold mineralised SIF was intersected at the predicted location from the model. / Geophysical survey information (magnetics, gravity, SAM and TEM) and anomalies in the Comet area were found to be primarily controlled by the local structures and mineralisation along these structures. Modelled ground TEM results were compared to TEMPEST airborne, EM data and showed reasonably similar patterns. The geophysical survey data also highlights black shale units, which can produce a false target commonly running parallel to the sulphide altered fault zones and SIF units, because of graphite and sulphide in the black shale. / The TEMPEST data were a valuable guide to bedrock conductivity over the outline project area at Comet, and the follow–up ground TEM and SAM survey data was very useful for accurately pin-pointing anomalies for drill testing. / Geophysical and geological data analysed in this study was used to generate a geophysical interpretation map at 1:5,000 scale. The new interpretation of geological units and structures at Comet will provide geologists with a better understand about the geological and structural setting for mineralisation in the Comet area. For example, the Comet Fault represents a faulted limb of the Comet fold structure that has both limbs dipping to the SE, and plunges to the NE. Magnetic anomalies associated with SIF are considered to correlate with some gold bearing horizons and the location of the Comet Fault, that has become more siliceous and altered by sulphide minerals and magnetite minerals. / It is recommended that other prospect areas in the region should be surveyed using the SAM method in order to identify shallow gold bearing structures and improve geological interpretations ahead of drilling.

Η παρούσα διπλωματική εργασία περιγράφει την έρευνα της θαλάσσιας γεωφυσικής διασκόπησης η οποία εκτελέστηκε στον Πατραϊκό κόλπο και παρουσιάζει τα αποτελέσματα της ερμηνείας των γεωφυσικών στοιχείων που συλλέχθηκαν με την βοήθεια του τομογράφου υποδομής πυθμένα. Τα στοιχεία συλλέχθηκαν από το Εργαστήριο Θαλάσσιας Γεωλογίας και Φυσικής Ωκεανογραφίας του τμήματος Γεωλογίας του Πανεπιστημίου Πατρών. Η συλλογή, επεξεργασία και ερμηνεία του συνόλου των σεισμικών γραμμών επέτρεψε την χαρτογράφηση των υποθαλάσσιων ρηγμάτων του Πατραϊκού κόλπου. Ο χάρτης με τα υποθαλάσσια ρήγματα αποτελεί έναν τροποποιημένο χάρτη από τον ήδη διαθέσιμο χάρτη ρηγμάτων του Πατραϊκού κόλπου του 1985 από τους Ferentinos et al., 1985. / The present study describes the submarine geophysical survey which was carried out in the Gulf of Patras and presents the results of the geophysical data analysis using a subbottom profiler system. The data were collected by the Laboratory of Marine Geology & Physical Oceanography, department of Geology, University of Patras. A detailed fault map was produced by the data analysis of the collected seismic profiles of the Gulf of Patras. The present fault map is a modified map from a former map that has been produced in a 1985 survey by Ferentinos et al., 1985.