The advent of the Global Positioning System (GPS) meant that, for the first time, the geodetic and geophysical community has a tool for measurements on a global, continental and national scale. Global GPS networks are already competing with VLBI and SLR for the measurement of inter-continental baselines and earth rotation parameters. The development of the 'high accuracy fiducial GPS technique', as described in this thesis, has produced results comparable with mobile VLBI and SLR systems, but in shorter observational periods and at lower costs. Combined with global GPS networks, which have the potential to provide time-tagged fiducial station coordinates at the observational epochs, coordinates can be determined in a global reference frame. The results in this thesis, from a fiducial GPS campaign to monitor the vertical land movement at tide gauge sites in the UK, demonstrate that millimetric precisions and accuracies can be obtained in all three components over baselines of hundreds of kilometers. The combination of GPS with existing 2-d classical triangulation networks for mapping, engineering surveying and navigation has caused many problems, since the GPS observations are 3-d and of a superior quality. In Europe these problems have been overcome by the establishment of a new high precision reference framework, EUREF, based on fiducial GPS carried out in 1989. This thesis also describes the determination of coordinates for the UK EUREF stations and their application for geodetic control in Great Britain.

Roads are an integral part of today's lifestyle. Indeed, a modern and efficient economy requires a satisfactory road network. The road network in the United Kingdom faces ever-increasing demands with 94% of passenger travel and 92% of freight transport undertaken by road. Maintenance of the network is essential. Prior to the commencement of any maintenance scheme, an accurate highway profile is measured by undertaking a detailed topographic survey of the road surface and the adjacent verges. Traditionally, this is carried out by land surveyors using, for example, a theodolite, EDM and level. Highway surveying by traditional methods is a slow, costly and dangerous process. A photogrammetric technique was devised by Photarc Surveys Ltd of Harrogate, UK to reduce the problems of speed, cost and safety. This helicopter based photographic system can yield topographic data at up to ±5mm rmse through photogrammetric analysis. It is necessary to install ground control points on the hard shoulder for use in the photogrammetric analysis. This research investigates the potential of both conventional aerial triangulation and in-flight GPS assisted aerial triangulation for reducing this ground control requirement. The original photographic system is extended to integrate a GPS positioning system and the performance of this system is assessed through a series of field trials. The results of the research show that the camera can be positioned by the GPS system to within 5 centimetres. The GPS positions can be included in the aerial triangulation to further reduce the requirement for ground control. It is shown that for mapping at the ± 5mm rmse level, there is no potential for height control reduction, even when GPS positions are used. However for mapping at up to ± 20mm, the GPS positions can enable a significant reduction in ground control.

Wide Area Differential GPS (WADGPS) aims at overcoming the main drawback of conventional DGPS, namely the limited range over which the differential corrections are valid, due to the rapid decorrelation of the error sources with increasing distance from the reference station to the user. In the WADGPS approach, error sources are generated for users over a large portion of the earth, such as a communication satellite's entire footprint, by separating and modelling the main sources of error in GPS measurements. This has the effect of eliminating the limit imposed on the validity of the corrections by the geographical or atmospheric environment. A main advantage of WADGPS is the fact that far fewer reference stations are needed to cover the same area, compared to conventional DGPS. Interest in WADGPS has grown during the last few years, the use of WADGPS both for positioning accuracy requirements and the provision of integrity are being explored. Several research establishments have come up with their own WADGPS methodology and algorithms, all sharing a basic principle, namely the requirement that different error sources which affect GPS navigation are dealt with separately, and their spatial and temporal properties are investigated and modelled individually. Research was carried out to develop an advanced method and the corresponding algorithms, which could provide a high precision WADGPS positioning service. The service would be suitable for single or dual frequency users, and could be introduced with very few reference stations. The two main components of the service are a precise, near real-time orbit determination of the GPS satellites, and an accurate estimation and modelling of ionospheric and tropospheric effects. Results from real data indicate that user position accuracy of the order of 2 m and 3 m (RMS) in plan and height components respectively, were achieved over user-reference distances ranging from 2,000 to 3,500 km.

Considerable interest has been show in the development and application of real time On-The-Fly (OTF) kinematic GPS. A major error source and limitation of such a positioning technique is that caused by cycle slips. When these occur, the integer ambiguities must be resolved for, which can take hundreds of epochs to complete depending on satellite availability and geometry. This research has focused on investigating the applications of real time OTF GPS, as well as its limitations and precision, which has been shown in the thesis to be precise to a few millimetres. The limitations of such a system at present include the use of UHF telemetry links, which at best have a line of sight range of -10 km. The research has shown that alternatives are required, and the use of a relay station can prove invaluable. Cycle slips are another major limiting factor when using OTF GPS, as once a cycle slip occurs, it can either be corrected for or the integer ambiguities resolved for. The second option can take hundreds of seconds, depending on the algorithms used and the satellite number and geometry. This research has partly focused on the development of software which will instantaneously detect and correct for cycle slips in high rate GPS data. The applications of real time OTF GPS are numerous. Research has been carried out to investigate its use to monitor and control construction plant as well as monitoring the movement of large structures. As OTF positioning is precise to a few millimetres, it is ideal for the control of construction plant, and has been compared to laser levelling and precise digital levelling. Such a GPS system gives the user a 3-dimensional position for the bulldozer blade, for example. Such information can prove invaluable for quality control as well as developing an automated system, which would be controlled by real time OTF GPS. In addition, real time OTF GPS has been shown in the research to provide instantaneous positioning of large structures in the form of bridges. Such information could provide future systems which would monitor the structure for dangerous movements, resulting in a failure alarm. Carrier phase kinematic GPS has previously been shown to work over baseline lengths of < 20 km. The use of Multiple Reference Stations (MRS) has been shown in this research to enable OTF GPS to be applied over longer baseline lengths, with a precision in the order of 12 cm over 132 km.

Very Long Baseline Radio Interferometry is one of the most recently developed and potentially most useful geodetic measuring techniques. The high accuracy which it can achieve over great distances makes it ideally suited. for studies of many interesting geodetic and geophysical phenomena. The major asset of the system is that, unlike the majority of other accurate techniques, all measurements are independent of the Earth's gravity field. This thesis contains details of the basic theory of the VLBI technique and describes a model which has been developed to analyse data from the system. This is followed by a description of the application of the variation of co-ordinates method to the adjustment of VLBI observations and details the conditions and restrictions to be applied to the adjustment process. The basic procedure and equipment required to make the observations is described and details are given of the Nottingham University Long Baseline Interferometry Programs (NULBIP) which have been developed to perform the data analysis. Data has been obtained and analysed from two independent sets of observations using two different VLBI observing systems. The Canadian system has been used for observations using the three antenna array comprising the Chilbolton Observatory, England, the Algonquin Radio Observatory, Canada, and the Owens Valley Radio Observatory, U. S. A. Observations have also been processed from the Haystack-Goldstone baseline in the U. S. A., observed using the NRAO Mk I VLBI system. The software which has been developed has been tested by comparison with independently derived results on these baselines. The analysis of all the data has shown the VLBI method to be a highly accurate technique capable of measuring intercontinental distances with sub-metre accuracy. The results have indicated the many potential uses of VLBI in geodetic and geophysical research, the major ones of which have been described. The magnitude of systematic scale and orientation errors inherent in the Navy Navigation Satellite System (otherwise known as the TRANSIT system) have been measured by comparing these VLBI results with satellite-Doppler results derived from observations made near the radio telescopes.

The influence of geometrical parameters on the development of intermittent flow is studied in this thesis. The geometrical parameters considered are the diameter of the pipe, the angle of inclination of the pipe, and the distribution of the area of the gas injection. Intermittent flow in gas-liquid two-phase flows occurs when, from a fixed point, a gas dominated structure followed by a liquid dominated structure seems to repeat at a certain mean frequency. It is mainly slug flow but churn and cap bubble flow also fall into this broad category. Intermittent gas-liquid two-phase flow was investigated in a 67 mm diameter, 6 m long rig and also in a 127 mm diameter, 12 m long rig. The test section of the 67 mm rig was mounted in a steel frame supported by a pivot that allowed changing the inclination of the pipe from vertical to horizontal in steps of 15°. The 127 mm rig can only be operated in the upwards vertical position. The fluids utilised were air and silicon oil of viscosity = 5 cP and density = 0.912 kg/m3. The interfacial surface tension was measured at 0.02 N/m. The facilities were both operated at atmospheric pressure. The gas superficial velocity (Ugs) was varied from 0.17 to 2.9 m/s and liquid superficial velocity (Uls) from 0.023 to 0.47 m/s. The void fraction generated by each set of conditions was captured for 60 seconds using a Wire Mesh Sensor and a twin plane Electrical Capacitance Tomography probe. The effect of the diameter and the angle of inclination of the pipe under different gas and liquid superficial velocities was reported. The main findings can be summarised as that the velocity of the periodic structures was found to be higher in large diameter pipes and increases with increasing the angle of inclination reaching a maximum around 50° then decreases. In addition, the frequency of the gas structures was found to be higher in small diameter pipes and increases with increasing the inclination of the pipe for all the gas and liquid superficial velocities investigated. Additionally, two correlations to predict the velocity and the frequency of the periodic gas structures as a function of the diameter, the inclination of the pipe, the gas superficial velocity and the liquid superficial velocity were developed. The proposed correlations were found to not only be in excellent agreement with the present experimental results (less than 20% difference), but also in good agreement with data published by other researchers. This include data produced using different fluids, different diameters of pipe and different gas and liquid superficial velocities to the ones investigated in this work. It was also found that the gas injection area, modified using different gas-liquid mixers, do not have an influence on the development of the intermittent two-phase flows at 75 diameters axial length from the mixing point.

Information about deformation in an area has become vital not only for safety assessment but also for maintenance of geodetic infrastructures. The latter is necessary to support accurate surveying and mapping applications. This research exploits the complementary features of Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) techniques to assess the long-term deformation in Johor, Malaysia, which can be induced by natural and/or anthropogenic activities. Furthermore, modelling and mitigation of tropospheric effects in GPS and InSAR are addressed to achieve the best possible precision from the two techniques. Indeed, their modelling and mitigation improve the quality of the estimation as well as provide valuable resources for atmospheric studies. The assessment of long-term deformation in Johor is firstly made by analysing the five years (2007 - 2011) point-specific profile at eight Malaysia Real-Time Kinematic GNSS Network (MyRTKnet) stations. Two processing strategies, namely Precise Point Positioning (PPP) and Double-Difference (DD), are employed to assess their capability for deformation monitoring. The latter also make used of the GPS data from 27 IGb08 stations and 7 International GNSS Service (IGS) stations. Analysis of the results revealed deformation that can be explained by plate tectonic movement and earthquakes in the surrounding region. While results from the PPP processing showed a higher correlation with the recorded earthquakes, the results from DD have improved correlation coefficients at about 4% in the East-West and 5% in the Up-Down components. These improvements are valuable when the rate of deformation is the primary interest. In addition to the point-specific profile, the surrounding deformation of Johor has been assessed with the line-of-sight (LOS) velocity maps from the InSAR time-series. Two sets of ERS-1/2 data, consisting a total of 67 images acquired at two descending tracks (i.e. track 75 and 347), are utilised for the generation of the maps. Moreover, the feasibility of Sentinel-1 satellites is also tested, which revealed improved coherence owing to their short revisit cycle. Some part of Johor showed subsidence and uplift trends, which also agreed with the literature. This information cannot be perceived by the GPS alone due to its limited coverage; hence, further attests to the benefit of their joint analysis. Numerous developments have been implemented in the in-house software (i.e. Punnet) such as the implementation of tropospheric correction, outlier’s rejection scheme, statistical analysis to identify the control point for phase unwrapping, and a new method to retrieve temporal evolution of deformation for a rapidly deforming area.

Annular flow is one of the most common two-phase flow regimes observed in industrial applications. In annular flow, the liquid flows partly as a thin film along the pipe wall and partly as droplets entrained in the turbulent gas core. Most of the previous studies about the characteristics of annular flow and the developed correlations were conducted using an air/water system. This thesis reports an investigation about the characteristics of the annular flow regime and a development of liquid film thickness measurement using an ultrasonic technique in air/water and air/silicone oil systems. Experiments were carried on an upward vertical annular flow test facility with 34.5 mm inner diameter (ID) using air/water and air/silicone oil two-phase systems. Time-varying of total pressure drop, liquid film thickness and wall shear stress were measured. The total pressure drop was measured using a remote seal differential pressure transducer and the wall shear stress was measured using a glue-on hot film sensor. An ultrasonic technique was developed to measure the liquid film thickness. It was evaluated using static and dynamic measurements. For static measurements, it was compared with the liquid film thickness calculated based on knowledge of liquid volume and area of the test rig. For dynamic measurements, it was compared with two well-known conductance measurement techniques (Multi Pin Film Sensor and concentric probe) in falling film and upward vertical annular flow test facilities respectively. The relative error between the ultrasonic technique and the other two techniques was within ±5%. A new processing method for ultrasonic measurement called Baseline removal method was developed for measuring liquid film thickness less than 0.5 mm. The influence of gas and liquid superficial velocities, viscosity and surface tension on the measured parameters was studied using both systems. Both systems showed similar trend behavior with increasing gas and liquid superficial velocities even there was a difference in fluid properties. The results were also compared with the existing correlations developed using an air/water system to predict each one of the measured parameters. Most of the tested correlations predicted the total pressure drop, liquid film thickness and wall shear stress with relative deviation of ±50% or even higher in some cases.

The interaction of a boundary with turbulence is a defining feature of many turbulent flows, resulting in a turbulent boundary layer which plays a prominent role in the production and dissipation of turbulence. Commonly, this interaction is dominated by the effects of mean shear. However, more subtle aspects of the interaction, such as effects associated with turbulent motions impinging onto the boundary, are still thought to play a key role in giving rise to the boundary layer structure. Unfortunately, these aspects of the interaction are currently poorly understood. A better understanding of these aspects of the interaction may be derived by isolating them from the effects of mean shear through the study of zero-mean-shear turbulence interacting with a boundary. This study reports experimental work investigating the interaction between oscillating-grid turbulence (OGT) and a solid impermeable boundary. OGT is a commonly used experimental tool that produces a turbulent flow which is approximately homogeneous and isotropic in planes parallel to the oscillating grid but which is inhomogeneous in planes perpendicular to the oscillating grid. Throughout this study, instantaneous velocity measurements of the flow are obtained by applying two-dimensional particle imaging velocimetry to the vertical plane through the centre of the oscillating grid. A detailed preliminary study to characterise the flow generated by the OGT apparatus is initially performed. Visualisation of the flow close to the oscillating grid indicates that large-scale circulations are induced in OGT by the merging of grid-induced jets close to the tank walls. The installation of an open-ended cuboidal `inner box' below the grid is shown to inhibit the merging of these jets, thereby resulting in a more regular jet structure close to the oscillating grid and a corresponding reduction in mean flow within the inner box. It is also found that, contrary to assumptions in the literature, this amendment to the standard OGT apparatus is most effective when the top of the inner box is located close to the oscillating grid. The reduction in mean flow intensity that results from the use of a correctly installed inner box brings about a turbulent flow in which the mean flow velocity components are small compared to velocity fluctuations, thereby enabling a meaningful comparison to be made with zero-mean-shear turbulence. Consequently, the interaction between OGT and a solid impermeable boundary is studied to derive insight into the mechanisms governing the interaction of zero-mean-shear turbulence with boundaries. Results indicate that a critical aspect of the interaction is the blocking of a boundary-normal flux of turbulent kinetic energy across the boundary-affected region, which acts to increase the magnitude of the boundary-tangential turbulent velocity components, relative to the far-field trend, but not the boundary-normal turbulent velocity component. This feature arises as a result of the anisotropic nature of the flow produced by OGT, whereby the turbulent fluctuations decay with distance normal to and away from the oscillating grid, and would not be present in a turbulent flow that was otherwise homogeneous above the boundary-affected region of the flow. This observation provides new insight into the validity of well-established models of the interaction of zero-mean-shear turbulence and a solid impermeable boundary and provides a physical mechanism that explains the disparity in previously reported measurements relating to this problem. The results reported are also in support of intercomponent energy transfer mechanisms previously proposed to govern the interaction of zero-mean-shear turbulence with boundaries, including viscous and `return-to-isotropy' mechanisms. That is, within a thin region adjacent to the boundary, approximately equal in thickness to the viscous sublayer, the data indicate that turbulent motions incident towards the boundary are more energetic than motions away, which are characteristics of an intercomponent energy transfer primarily driven by the viscous dissipation of turbulent kinetic energy. In addition, at the edge of the boundary-affected region, where the magnitude of the boundary-tangential turbulent velocity components exceeds the magnitude of the boundary-normal turbulent velocity component, results indicate that an intercomponent energy transfer occurs from the boundary-tangential turbulent velocity components to the boundary-normal turbulent velocity component in a so-called `return-to-isotropy' energy transfer. However, the data also indicate the presence of an additional intercomponent energy transfer, from the boundary-normal turbulent velocity component to the boundary-tangential turbulent velocity components over a thin region outside the viscous sublayer. Comparison to previously published results of related studies indicates that this mechanism is also prevalent in previous work, but is not captured within existing models of intercomponent energy transfer at the boundary. Results further indicate that the intercomponent energy transfer mechanisms are not independent of the blocking of the boundary-normal turbulent kinetic energy flux. That is, the blocking of the boundary-normal turbulent kinetic flux promotes anisotropy within the boundary-affected region of the flow and thereby induces a stronger `return-to-isotropy' energy transfer mechanism. Hence, the effect of a solid impermeable boundary on turbulent velocity components in zero-mean-shear turbulence depends critically on the nature of the original turbulent field (i.e. homogeneous or inhomogeneous turbulence).

Oil and water separation processes in primary separators and transportation of these fluids through pipelines for further processing, is very vital but has often proved problematic due to changes in composition of the fluids together with build-up of sand or asphaltenes, in many petroleum industries. These separator vessels are large and cost effective to install together with safety implications due to equipment failure. Hence an understanding of the two-phase flow dynamics and motivation to improve upon their design and performance is necessary. Therefore, the main aim of this research programme is to investigate the coalescence efficiencies of droplet size in both stirred tank and horizontal pipe line under turbulence in oil-water two phase systems and also to determine the possibility of using a compact sudden pipe expansion as a phase separator for converting dispersed flow to segregated flow. For the purpose of experimental investigations, a sudden pipe expansion rig was designed, constructed and commissioned in L3 main laboratory of the department of Chemical and Environmental Engineering, University of Nottingham, UK. The fluids used are tap water ( ; ) and silicone oil 5cp, ( ; ) at operating conditions for mixture velocities between 0.20 ms-1 – 3.50 ms-1 and input oil volume fraction from 20% OVF to 80% OVF at different pipe inclinations (+40, +20, 00, -20,-40). Ring conductance probes were used to obtain phase layer distribution information of the oil-water flow together with the backscatter Lasentec FBRM M500P laser for drop size measurements and Phantom PCC 2.7 high speed camera for imaging. In both horizontal and upward inclined flows, the input oil volume fraction and mixture velocity strongly influenced the formation of drop sizes downstream of the expansion, due to coalescence mechanism. Coalescence of both oil and water dispersed phase droplets and segregation was found to start at short distance from the inlet section and progresses gradually downstream of the pipe expansion. The water droplets coalesce and settles faster than dispersed oil droplets in water continuous phase flow system and also the bulk oil layer was observed to flow faster at the top than the bottom water layer for the horizontal and upward flow conditions. Therefore the results reveals a strong influence of mixture velocity, input oil volume fraction and pipe angle inclination on drop break up and coalesce mechanisms in oil-water flow systems. The results obtained satisfactorily agree well with the existing conventional flow patterns and flow pattern maps. The flow patterns identified includes, stratified flow (ST), stratified with mixed interface (ST& MI), oil-water intermittent flow, stratified wavy flow and dispersed flow in all pipe orientations. Additional flow patterns were also observed such as Raleigh Taylor ‘plume shaped’ flow in the horizontal flow and plug wavy flow (Caterpillar like waves) in both upward and downward inclination, which have not been reported in large diameter pipes. There was evidence of stratification for fully developed ST regime at short distance from inlet (10D) at mixture velocities below 0.30ms-1 in both horizontal and upward inclinations. Therefore, in order to achieve stratified flow in oil-water two-phase flow system, a sudden pipe expansion was used successfully to convert a dispersed flow to segregated flow within a 6m long test pipe distance. The best orientation was that of the horizontal flow position for dispersed flows to separate quickly as both the upward and downward inclined pipe flow conditions tend to hamper the evolution process by increasing the mixed layer region.