Dissertations / Theses on the topic 'Ground-based'
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Yarham, Carson, Urs Boeniger, and Felix J. Herrmann. "Curvelet-based ground roll removal." Society of Exploration Geophysicists, 2006. http://hdl.handle.net/2429/545.
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We have effectively identified and removed ground roll through a twostep
process. The first step is to identify the major components of the
ground roll through various methods including multiscale separation,
directional or frequency filtering or by any other method that identifies
the ground roll. Given this estimate for ground roll, the recorded
signal is separated during the second step through a block-coordinate
relaxation method that seeks the sparsest set for weighted curvelet coefficients
of the ground roll and the sought-after reflectivity. The combination
of these two methods allows us to separate out the ground roll
signal while preserving the reflector information. Since our method is
iterative, we have control of the separation process. We successfully
tested our algorithm on a real data set with a complex ground roll and
reflector structure.
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Henehan, Michael J. "Ground-truthing the boron-based proxies." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/359133/.
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Schüler, Torben. "On ground based GPS tropospheric delay estimation." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963624393.
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Grant, Stanley E. "Performance evaluation of ground based radar systems." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA283654.
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Thesis (M.S. in Systems Technology (Command, Control, and Communications)) Naval Postgraduate School, June 1994.Thesis advisor(s): F. H. Levien, Dan C. Boger. "June 1994." Includes bibliographical references. Also available online.
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Hagelin, Susanna. "Optical Turbulence Characterization for Ground-Based Astronomy." Doctoral thesis, Uppsala universitet, Institutionen för geovetenskaper, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132798.
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The optical turbulence, which creates perturbations of the wavefronts coming from the stars, is caused by small-scale fluctuations in the index of refraction of the atmosphere and is a problem for astronomers because it limits the maximum resolution of the ground-based telescopes. One way of identifying the best sites to build astronomical observatories, where the influence of the optical turbulence is as small as possible, is to use the standard meteorological parameters to get a first idea of the potential of a site. In the first part of this thesis the three sites on the Internal Antarctic Plateau that are the most interesting for astronomers (Dome A, Dome C and the South Pole) are investigated using the operational analyses of the ECMWF and a ranking of these three sites is presented. The second part of this thesis focuses on the ability of the mesoscale model Meso-NH to simulate the optical turbulence as well as the wind speed at Mt Graham (AZ, USA). A rich sample of measurements of the vertical distribution of the optical turbulence, the largest sample used in this type of study so far, is used to calibrate the Meso-NH model and to quantify its ability to simulate the optical turbulence. The measurements are distributed over different periods of the year thus making it possible to evaluate the performance of the model in different seasons. Both the vertical distribution of the optical turbulence and the astroclimatic parameters (seeing, wavefront coherence time and isoplanatic angle) are investigated.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 708
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Matcham, Jeremy Stephen. "Ground based laboratory atomic oxygen calibration experiments." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286766.
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Seki, Daikichi. "Space Weather Prediction Using Ground-Based Observations." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263804.
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付記する学位プログラム名: 京都大学大学院思修館京都大学
新制・課程博士
博士(総合学術)
甲第23343号
総総博第16号
京都大学大学院総合生存学館総合生存学専攻
(主査)教授 山敷 庸亮, 教授 寶 馨, 准教授 浅井 歩
学位規則第4条第1項該当
Doctor of Philosophy
Kyoto University
DFAM
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Monserrat, Hernández Oriol. "Deformation measurement and monitoring with Ground-Based SAR." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/81557.
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The Ground-Based Synthetic Aperture Radar (GB-SAR) is a relatively new technique,
which in the last ten years has gained interest as deformation measurement and
monitoring tool. The GB-SAR technique is based on an imaging radar-based sensor, which
o ers high sensitivity to small displacements, in the region of sub-millimetres to
millimetres, long-range measurements, which can work up to some kilometres, and massive
deformation measurement capability. These features confer to the GB-SAR technique
interesting advantages with respect to other point-wise deformation measurement
techniques.
The process of estimating deformation from the GB-SAR data is not straightforward:
it requires complex data processing and analysis tools. This dissertation is focused on
these tools, covering the whole deformation estimation process. This thesis collects the
main research results achieved on this topic during my work at the Active Remote Sensing
Unit of the Institute of Geomatics. Two di erent approaches for measuring deformation
with GB-SAR data are described and discussed. The irst one is the interferometric
approach, based on the exploitation of the phase component of the GB-SAR data, which
is the commonly used GB-SAR method. The second one is a non-interferometric approach,
which exploits the amplitude component of the GB-SAR data, o ering an interesting
alternative way to exploit the GB-SAR data.
This dissertation has two main objectives. The first one is presenting, step by step, a
complete interferometric GB-SAR procedure for deformation measuring and monitoring.
The second one is presenting two new algorithms, which represent the most innovative
part of this thesis. The first algorithm faces the phase unwrapping problem, providing an
automatic solution for detecting and correcting unwrapping errors, which is called 2+1D
phase unwrapping. The second algorithm is the base of the above mentioned non-
interferometric approach, which overcomes some of the most critical limitation of GB-SAR
interferometry, at the expense of getting less precise deformation estimates.
The dissertation is divided in 6 chapters. The first one is the introduction, while the
second one provides an overview of GB-SAR interferometry, introducing the main aspects
that are the basics of the subsequent chapters. Chapter 3 describes a complete GB-SAR
processing chain. Chapters 4 and 5 contain the most original part of the dissertation, i.e.
the 2D+1 phase unwrapping algorithm, and the non-interferometric approach. Finally, in
Chapter 6 the conclusions are discussed and further research is proposed.El radar terrestre d’obertura sintètica (GB-SAR) és una tècnica relativament nova que, en els últims deu anys, ha guanyat interès com a eina per a mesurar i monitorar deformacions. La tècnica GB-SAR es basa en un sistema radar amb capacitat per proporcionar imatges, que ofereix una alta sensibilitat a petits desplaçaments, d’ordre mil·limètric o submil·limètric, que és capaç de mesurar a llargues distàncies (alguns km) i que té una alta capacitat per fer mesures massives. Aquestes característiques donen a la tècnica interessants avantatges respecte a altres tècniques clàssiques de mesura de deformacions, típicament basades en mesures puntuals. Derivar mesures de deformació a partir de dades GB-SAR no és un procés senzill, ja que requereix uns procediments complexos de processat i anàlisi de dades. Aquesta tesi es centra en aquests processos. Aquesta tesi recull alguns dels resultats més destacats de la investigació que he desenvolupat sobre aquest tema a la unitat de Teledetecció Activa de l'Institut de Geomàtica. Al llarg del document es descriuen dues aproximacions diferents per mesurar deformacions amb GB-SAR. Una es basa en la explotació de la tècnica de la interferometria, és a dir explotant la component de la fase de les imatges GB-SAR: és la tècnica GB-SAR usada habitualment. La segona, anomenada tècnica no-interferomètrica, es basa en la component de l’amplitud de les dades GB-SAR i ofereix una interessant alternativa a la primera. La tesi acompleix dos objectius principals. En primer lloc presenta un procediment complet per la mesura i monitoratge de deformacions mitjançant interferometria GB-SAR. En segon lloc, descriu dos nous algorismes que resolen problemes específics de la interferometria clàssica aplicada al GB-SAR i que representen la part més innovadora d’aquesta tesi. El primer algorisme aborda un dels problemes oberts de la interferometria, el phase unwrapping, proposant un mètode automàtic per detectar-ne i corregir-ne els errors. El segon algorisme proposa un nou mètode per a l'explotació de les dades GB-SAR per mesurar deformacions sense utilitzar la interferometria. La estructura de la tesi consisteix en sis capítols. Després de la introducció, el Capítol 2 proporciona una visió general de la interferometria GB-SAR, introduint els conceptes principals utilitzats en la tesi. En el tercer capítol es descriu una cadena de processament basada en GB-SAR interferomètric. Els capítols quart i cinquè contenen la part més original de la tesi: l'algorisme de phase unwrapping i el mètode no-interferomètric per la mesura de deformacions. Finalment, es discuteixen les conclusions principals i es proposen futures línies d’investigació.
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Pipia, Luca. "Polarimetric differential SAR Interferometry with ground-based sensors." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/6951.
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Las técnicas de Interferometría Diferencial se basan en la combinación de varias imágenes SAR con distinta separación temporal y permiten la recuperación de las componentes lineales y no-lineales del proceso de deformación ocurrida en el entorno de interés durante el entero periodo de observación. Condición imprescindible para una correcta estimación de los fenómenos geodéticos es la elevada estabilidad de la plataforma que embarca el sensor SAR. Por esta razón, a nivel operativo se utilizan datos SAR satelitales.El objetivo de la Polarimetría SAR es describir el entorno de interés analizando las propiedades de la señal que éste dispersa cuando se utilizan diferentes combinaciones de polarización de las antenas transmisora y receptora, definidas canales polarimétricos. La polarimetría interferométrica SAR junta la capacidad de la polarimetría de separar mecanismos de dispersión independientes con la sensibilidad de la Interferometría a la altura de los correspondientes centros de fase, y permite describir la distribución volumétrica de los dispersores dentro de la escena observada. Debido a la falta de conjuntos de datos polarimétricos SAR satelitales que cubran tramos temporales suficientemente largos, hay aún un gran interés en las mejoras que la polarimetría podría aportar a técnicas ya consolidadas como las de Interferometría Diferencial.
La actividad de investigación que se presentará en esta tesis doctoral abarca, por primera vez conjuntamente, las dos áreas de la Polarimetría SAR y de la Interferometría Diferencial utilizando el sensor radar terrestre de corto alcance (gbSAR) desarrollado por la Universitat Politècnica de Catalunyua (UPC). El trabajo constará de dos bloques principales.
El primer bloque describirá las técnicas que se han desarrollado para convertir el sistema UPC gbSAR en un instrumento operativo y simplificar la utilización de sus adquisiciones, incluyendo la formulación matemática de los principios de funcionamiento del sistema, la cadena de procesado de los raw data y su calibración polarimétrica, los procedimientos de georeferenciación, y las técnicas de compensación de los artefactos atmosféricos presentes en sus medidas diferenciales.
La segunda parte se ocupará de demostrar los beneficios que los datos SAR polarimétricos ofrecen respecto a la medición de un único canal polarimétrico para aplicaciones diferenciales. A fin de llevar a cabo esta tarea, se analizarán los datos gbSAR adquiridos durante una campaña de medidas de un año realizada en el pueblo de Sallent, en Cataluña, afectado por un fenómeno de subsidencia. En esta parte se analizarán tres temas principales. El primero es el comportamiento no estacionario en tiempo del entorno urbano bajo la geometría de observación del sensor terrestre. Se estudiarán en detalle los efectos de su inestabilidad y se propondrá una técnica de filtrado novedosa entallada a las propiedades de los blancos deterministas con el fin de preservar la información de la fase diferencial. El segundo tema abarca el problema de los efectos de troposfera en datos diferenciales con separación temporal superior al mes y de su separación de las variaciones de fase inducidas por el proceso de deformación. El tercer tema es la utilización de toda la información polarimétrica diferencial. Con fin de superar las limitaciones propias de las técnicas DInSAR clásicas, se propondrá un nuevo modelo polarimétrico de dispersión y se demostrarán las ventajas de la nueva formulación enseñando la mejor estimación del proceso de subsidencia en Sallent. En la parte final de este apartado se explorará también el potencial de las técnicas polarimétricas de optimización de la coherencia para aplicaciones diferenciales.
Differential SAR interferometry (DInSAR) deals with the combination of multi-temporal SAR images for the estimation of the linear and non-linear components of the deformation process within an area of interest during the whole observation period. A high stability of the platform is required for a reliable estimation of the geodetic phenomena. Accordingly, space-borne SAR images are operatively employed for DInSAR estimation, air-borne DInSAR still constituting a challenging research issue. SAR
Polarimetry aims at charactering the illuminated area through the analysis of its response under different combinations of transmitting and receiving antennas polarization, called polarimetric channels. The Polarimetric SAR Interferometry joins the capability of Polarimetry to separate independent scattering mechanisms and the sensitivity of Interferometry to the corresponding phase centers' elevation, making it possible to describe the volumetric distribution of the scatterers within the observed area. Owing to the lack of long-time collections of polarimetric space-borne SAR data, the studies carried out in this research field have been mainly based on air-borne acquisitions. Yet, there is a great expectation for the improvements that polarimetry may bring to assessed single-polarization techniques such as the DinSAR.
The research described in this PhD dissertation fills for the first time the gap between SAR Polarimetry and SAR Differential Interferometry through the employment of an X-band ground-based SAR (gbSAR) sensor developed by the Remote Sensing Lab of the Universitat Politècnica de Catalunya (UPC).
The work is divided into two main blocks. The first part deals with the algorithms that have been developed to make the UPC system operative and its acquisitions easy to use. Summarily, they include the mathematical formulation of the sensor's working principles, the raw data processing chain and the polarimetric calibration method, the geocoding procedures, and the techniques compensating for the atmospheric artefacts affecting gbSAR zero-baseline acquisitions.
The second part is concerned with demonstrating the benefits that polarimetric SAR measurements provide with respect to single-polarization data for differential applications. In order to cope with this task, the data sets acquired during a one-year measurement campaign carried out in the village of Sallent, northeastern Spain, are analyzed. The experiment was focused on monitoring the subsidence phenomenon affecting a district of the village with the UPC gbSAR sensor. Three main issues are here argued. The first one is the time non-stationary behaviors characterizing the urban environment at X-band in the gbSAR observation geometry. Their effects are analyzed in detail and a novel non-stationary filtering technique tailored to deterministic scatterers' properties is introduced to preserve the differential phase information. The second one is the compensation of the troposphere changes in long-time span gbSAR differential interferograms. A new technique is worked out to effectively separate the differential phase variations due to the atmospheric artefacts from the deformation components. The third one is the use of the whole polarimetric differential information. A novel polarimetric differential scattering model is put forward to relax the constraints of an advanced DInSAR technique, the Coherent Pixel Technique, and to propose an innovative polarimetric approach. The advantages offered by Polarimetric DInSAR are demonstrated in terms of quality of the deformation-rate map describing the subsidence phenomenon in Sallent. In the end, the potentials of coherence-optimization techniques for the further improvement of the deformation process estimation are stressed.
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Ho, Sze-Tek Terence. "Investigating ground swarm robotics using agent based simulation." Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FHo.pdf.
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Thesis (M.S. in Operations Research)--Naval Postgraduate School, December 2006.Thesis Advisor(s): Susan M. Sanchez. "December 2006." Includes bibliographical references (p.111-114). Also available in print.
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Ekblad, Ulf. "Earth satellites and air and ground-based activities." Doctoral thesis, KTH, Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3775.
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This thesis, Earth satellites and detection of air andground based activities by Ulf Ekblad of the Physics departmentat the Royal Institute of Technology (KTH), addresses theproblem of detecting military activities in imagery. Examplesof various techniques are presented. In particular, problemsassociated with "novelties" and "changes" in an image arediscussed and various algorithms presented. The imagery usedincludes satellite imagery, aircraft imagery, and photos offlying aircraft.
The timely delivery of satellite imagery is limited by thelaws of celestial mechanics. This and other information aspectsof imagery are treated. It is e.g. shown that dozens ofsatellites may be needed if daily observations of a specificsite on Earth are to be conducted from low Earth orbit.
New findings from bioinformatics and studies of small mammalvisual systems are used. The Intersecting Cortical Model (ICM),which is a reduced variant of the Pulse-Coupled Neural Network(PCNN), is used on various problems among which are changedetection. Still much more could be learnt from biologicalsystems with respect to pre- and post-processing as well asintermediate processing stages.
Simulated satellite imagery is used for determining theresolution limit for detection of tanks. The necessary pixelsize is shown to be around 6 m under the conditions of thissimulation.
Difference techniques are also tested on Landsat satelliteimagery with the purpose of detecting underground nuclearexplosions. In particular, it is shown that this can easily bedone with 30 m resolution images, at least in the case studied.Satellite imagery from SPOT is used for detecting undergroundnuclear explosions prior to the detonations, i.e. under certainconditions 10 m resolution images can be used to detectpreparations of underground nuclear explosions. This type ofinformation is important for ensuring the compliance of nucleartest ban treaties. Furthermore, the necessity for havingcomplementary information in order to be able to interpretimages is also shown.
Keywords: Remote sensing, reconnaissance, sensor,information acquisition, satellite imagery, image processing,image analysis, change detection, pixel difference, neuronnetwork, cortex model, PCNN, ICM, entanglement, Earthobservation, nuclear explosion, SPOT, Landsat, verification,orbit.
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Partamies, Noora. "Meso-scale auroral physics from ground-based obervations /." Helsinki : Finn. Meteorological Inst, 2004. http://www.gbv.de/dms/goettingen/472841971.pdf.
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Goudarzi, Atousa. "Space and ground based studies of transpolar arcs." Thesis, University of Leicester, 2009. http://hdl.handle.net/2381/7398.
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This thesis presents a study of the formation and dynamics of 6 transpolar arcs. This work was undertaken primarily using auroral emission data from the Imager Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft along with the ionospheric convection flow patterns from the Super Dual Auroral Radar Network HF radars located in the auroral regions of both hemispheres. Particle precipitation data from Defence Meteorological Satellite Program (DMSP) and National Oceanic and Atmosphere Administration (NOAA) satellites were also used, together with Field Aligned Current data from the Iridium satellite constellation. A detailed study is first presented concerning the nature of the ionospheric convection flows on the nightside during an isolated transpolar arc. The results of this study demonstrated: a) the occurrence of cross midnight azimuthal flows, which are thought to be associated with the formation of the transpolar arc; and b) that ionospheric flows caused by dayside reconnection were responsible for the motion of the transpolar arcs. Five further case studies of transpolar arcs, which exist during intervals of northward but different IMF By components, are also discussed. The flows during a number of transpolar arc events have been studied, which confirm that the excitation of flow appears to accompany transpolar arc dynamics in general. Also, a detailed study of particle precipitation data suggests that the particles associated with the transpolar arcs are located on closed field lines. Evidence presented in this thesis suggests that the transpolar arcs mentioned above lie on closed field lines. Finally, a discussion of possible future work is given, suggested by the results of the studies described above.
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Park, Hyun Kyoo. "NPSNET : real-time 3D ground-based vehicle dynamics." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23992.
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Haniff, Christopher Allim. "High-resolution imaging with ground-based optical telescopes." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238537.
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Hidalgo, Larsson Anna. "Forward Modelling of Ground Based SST Telescope Images." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302729.
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Space debris is becoming an increased threat to the future use of space orbits. In order to counteract this threat, the field of Space Situational Awareness (SSA), and the sub-field Space Surveillance and Tracking (SST), have been developed to gather knowledge about the space debris and satellites surrounding Earth. The orbit of a satellite can be determined by acquiring images of the satellite using a telescope and a sensor. During this thesis, a tool has been programmed in Python. This tool can simulate these types of images of satellite passes, at a given time and location. The simulator takes the system parameters of the telescope and camera sensor into account, together with several different types of disturbances which affect these images. The project has been carried out at the Swedish Space Corporation (SSC), which recently launched an SSA initiative. They plan to use these images to learn more about their upcoming observations, and possibly to test an orbit determination software.Rymdskrot är ett allt mer påtagligt hot mot den framtida användningen av om-loppsbanor i rymden. För att motverka detta hot har det blivit viktigt att kartlägga rymdlägesbilden och de objekt som ligger i omloppsbana runt jorden. Detta görs genom att observera, identifiera och banbestämma satelliter. En satellits omlopps-bana kan bestämmas genom att ta bilder av satelliten med hjälp av ett teleskop och en sensor. Under detta examensarbete har ett verktyg för att kunna simulera sådana bilder utvecklats. Simuleringsverktyget har programmerats i Python och kan simulera bilder av satellitpass vid en given tidpunkt och från en given plats. Verktyget tar hänsyn till systemparametrarna för teleskopet och kamerasensorn, samt effekterna av ett flertal olika typer av störningar som påverkar dessa bilder. Projektet har genomförts hos företaget Swedish Space Corporation (SSC), som nyligen lanserade ett initiativ för att bättre förstå rymdlägesbilden. De planerar att använda dessa bilder för att lära sig mer om deras kommande observationer, samt att eventuellt testa en programvara för att bestämma banparametrar.
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Haddock, Michelle. "Inductive Monitoring Systems: A CubeSat Ground-Based Prototype." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1515.
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Inductive Monitoring Systems (IMS) are the newest form of health monitoring available to the aerospace industry. IMS is a program that builds a knowledge base of nominal state vectors from a nominal data set using data mining techniques. The nominal knowledge base is then used to monitor new data vectors for off-nominal conditions within the system. IMS is designed to replace the current health monitoring process, referred to as model-based reasoning, by automating the process of classifying healthy states and anomaly detection. An IMS prototype was designed and implemented in MATLAB. A verification analysis then determined if the IMS program could connect to a CubeSat in a testing environment and could successfully monitor all sensors on board the CubeSat before in-flight use. This program consisted of two main algorithms, one for learning and one for monitoring. The learning algorithm creates the nominal knowledge bases and was developed using three data mining algorithms: the gap statistic method to find the optimal number of clusters, the K-means++ algorithm to initialize the centroids, and the K-means algorithm to partition the data vectors into the appropriate clusters. The monitoring algorithm employed the nearest neighbor searching algorithm to find the closest cluster and compared the new data vector with the closest cluster. The clusters found were used to establish the knowledge bases. Any data vector within the boundaries of the clusters was deemed nominal and any data vector outside the boundaries was deemed off-nominal. The learning and monitoring algorithms were then adapted to handle the data format used on a CubeSat and to monitor the data in real time. The developed algorithms were then integrated into a MATLAB GUI for ease of use. The learning and monitoring algorithms were verified with a 2-dimensional data set to ensure that they performed as expected. The final IMS CubeSat prototype was verified using 56-dimensional emulated data packages. Both verification methods confirmed that the IMS ground- based prototype was able to successfully identify all off-nominal conditions induced into the system.
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Altintas, Suleyman Serkan. "Attenuation Relationship For Peak Ground Velocity Based On Strong Ground Motion Data Recorded In Turkey." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12608067/index.pdf.
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Estimation of the ground motion parameters is extremely important for engineers to make the structures safer and more economical, so it is one of the main issues of Earthquake Engineering. Peak values of the ground motions obtained either from existing records or with the help of attenuation relationships, have been used as a useful parameter to estimate the effect of an earthquake on a specific location.
Peak Ground Velocities (PGV) of a ground motion is used extensively in the recent years as a measure of intensity and as the primary source of energy-related analysis of structures. Consequently, PGV values are used to construct emergency response systems like Shake Maps or to determine the deformation demands of structures.
Despite the importance of the earthquakes for Turkey, there is a lack of suitable attenuation relationships for velocity developed specifically for the country. The aim of this study is to address this deficiency by developing an attenuation relationship for the Peak Ground Velocities of the chosen database based on the strong ground motion records of Turkey. A database is processed with the established techniques and corrected database for the chosen ground motions is formed. Five different forms of equations that were used in the previous studies are selected to be used as models and by using nonlinear regression analysis, best fitted mathematical relation for attenuation is obtained.
The result of this study can be used as an effective tool for seismic hazard assessment studies for Turkey. Besides, being a by-product of this study, a corrected database of strong ground motion recordings of Turkey may prone to be a valuable source for the future researchers.
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Pfrommer, Thomas. "Mesospheric dynamics and ground-layer optical turbulence studies for the performance of ground-based telescopes." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/30467.
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Modern astronomical instrumentation employs adaptive optics (AO) systems that correct for atmospheric distortion in real time in order to produce sharper images. The design and performance of these systems relies on the knowledge of the atmosphere both at low and high altitude. This thesis investigates the first kilometer of the atmosphere, the ground layer (GL), as well as the sodium layer at ~92 km. Newly-designed lunar scintillometers provide turbulence profiles of the GL, and high spatio-temporally resolved sodium profiles are obtained using a newly-designed lidar system for UBC's 6-m liquid-mirror.
For ground layer adaptive optics systems, knowledge of the local height- and time-resolved GL turbulence is crucial to link local topography to optical turbulence and has been obtained with the help of three lunar scintillometers deployed in Chile, Hawaii and in the Canadian High Arctic. Results from measurements inside the Canada-France-Hawaii Telescope (CFHT) dome indicate severe degradation of image quality due to a poorly vented dome and thus provide input for dome modifications. The outside median GL seeing was determined to be 0.48±0.01". Initial results from the Arctic show exceptional GL seeing conditions, better than have been found anywhere on Earth although data quantity is limited.
Extremely large telescopes must correct not only for GL turbulence, but also higher atmospheric disturbances in the troposphere. The use of laser guide stars (LGS) increases sky coverage and the field of view, but relies on resonantly excited sodium atoms in the mesosphere. Upper atmospheric dynamics causes varying sodium density, which produces focus-induced wavefront errors in LGS AO systems. The UBC lidar system was built, and its high-resolution data reveal large spatial variability, strong nightly variations and meteor spikes in sodium density on sub-second time scales. The mean altitude power spectrum has been extended to scales approaching the dissipation limit, and its spectral index of -1.95±0.12 and normalization of 30±20 m²/Hz determines AO system wavefront errors of 4 nm for a 30 m, and 8 nm for a 42 m telescope per meter mean-altitude variation. Derived mean altitudes, separated by one arcmin, showed rms fluctuations of order 30 m and could cause AO performance degradation.
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McCabe, Stephen Joseph. "Ground based spectro-radiometry for studies of atmospheric scattering." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299249.
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Hewison, Tim J. "Profiling temperature and humidity by ground-based microwave radiometers." Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654501.
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Marchant, Jonathan. "A study on ground-based optical space debris detection." Thesis, University of Kent, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300773.
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Walker, Simon R. "Analysis and optimisation of ground based transiting exoplanet surveys." Thesis, University of Warwick, 2013. http://wrap.warwick.ac.uk/60463/.
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One of the most surprising aspects of the exoplanet population is the existence of Jupiter sized planets orbiting close to their parent stars. It is currently uncertain how these planets reached such small separations, and they are thought to be markers for the dominant migration mechanism. The Wide Angle Search for Planets (WASP) project is ideally suited for studying these planets, as it has detected the largest number of hot Jupiters to date. I have inverted the observed sample of WASP planets to calculate the underlying population of hot Jupiters through a quantitative study of the selection biases in the WASP project. To achieve this, I synthesised transiting systems and inserted them into WASP data to calculate the probability of detection. The observed population ofWASP planets is then corrected through application of this probability to determine the underlying population. I find a clear pile up in the underlying population at orbital periods between 3 to 5 days, and apply a joint constraint with the underlying population measurement from the Kepler project to propose a new model for the underlying population of giant planets. I propose a model consisting of a rising power law win period with index 1:0 - 0:3, with a Gaussian excess at 3:7 - 0:1 days to model the period pile up. The observed period pile up places crucial constraints on models of hot Jupiter migration. The Next Generation Transit Survey (NGTS) is a new transiting exoplanet survey designed to find Neptunes and super Earths around nearby stars. These stars will be bright, allowing the characterisation of the bulk densities and atmospheric compositions by current and next generation instruments. These planets are numerous but they cause shallow transits, so we must achieve a higher level of precision than has been previously achieved by a wide angle ground based survey. To test the design characteristics and that the required high levels of precision would be achieved, prototype instruments were constructed on La Palma and Geneva. We found that we were able to reach < 0:1% precision on an ensemble of bright stars on the typical transit timescales, indicating that the instrument will be capable of detecting smaller planets. We use Monte Carlo simulations coupled with a detectability analysis to predict that NGTS will detect 200 Neptunes and 30 super Earths with the next generation instrument ESPRESSO.
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Skelton, Michael T. "AN INTEGRATED GROUND BASED DATA ACQUISITION AND REDUCTION SYSTEM." International Foundation for Telemetering, 1985. http://hdl.handle.net/10150/615724.
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International Telemetering Conference Proceedings / October 28-31, 1985 / Riviera Hotel, Las Vegas, NevadaAn integrated ground data acquisition and reduction facility for monitoring rocket motor testing is being implemented for a large commercial client at their northern Utah test site. This system is capable of recording and processing in near real time large amounts of data from varied types of instrumentation. The system was developed as a stand alone data gathering and processing center and consists of one-of-a-kind integrating hardware, commercial off-the-shelf hardware and a DEC VAX 11-750 based computer system for data processing. This paper discusses the design of the system, the real time acquisition of data, and user friendly data reduction system.
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Burton, John Robert. "Ground-based investigations of the atmospheres of extrasolar planets." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669663.
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In this thesis, I present three main results which demonstrate significant development in the field of exoplanet atmosphere detection and modelling. A model for estimating the distortion of hot-Jupiter exoplanets due to the gravitational attraction by the host star solely based on observable parameters of transiting systems. The most significant case of distortion is that of the exoplanet WASP-12b which shows a bulk density over-estimation of 12%. In order to investigate the systematic sources of error associated with ground-based observations, the secondary eclipse of the transiting hot- Jupiter WASP-19b was observed, and found to have an eclipse depth of O.88±O.19mmag based on a single observation. Whilst this does represent a significant result, the systematics present in the data support further observations to better constrain the depth, duration and timing of the secondary eclipse. The final result presented in this thesis is a pilot study of the technique of 'defocussed transmission spectroscopy', a method of observation which is designed to allow for the detection of elements in the atmospheres of transiting extra-solar planets from groundbased platforms. I present limits on the detectability of sodium in exoplanet atmospheres, and provide a detailed investigation into the systematics associated with this novel observing technique. I also make recommendations as to how future observations can be improved, and present a possible detection of sodium in the atmosphere of WASP-12b with an absorption depth of O.12±O.03%.
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Wang, Kainan. "Piezoelectric Adaptive Mirrors for Ground-based and Space Telescopes." Doctoral thesis, Universite Libre de Bruxelles, 2019. https://dipot.ulb.ac.be/dspace/bitstream/2013/282015/3/ToC.pdf.
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This thesis investigates various active control aspects of large aperture telescopes; both Earth-based and space telescopes are considered.The first part proposes a concept of piezoelectric adaptive thin shell reflector for future space telescopes; it exhibits excellent areal density and stowability, and thus, paves the way to future large aperture space telescopes. Controlling the surface figure of spherical or parabolic shell with in-plane stresses induced by a piezoelectric layer raises two problems: (i) Doubly curved shells are significantly stiffer than flat plates (especially for the optical modes associated with hoop strains) and (ii) When using segmented electrodes with different voltages, the surface figure is subject to edge fluctuations with a characteristic length depending on the reflector curvature R_c and thickness t according to sqrt(R_ct). Accurate surface figure corrections require that the electrode size D_e satisfies D_eDoctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Roberts, Christopher. "Improving ground based test simulations of aerodynamically induced vibration." Thesis, University of Bristol, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.752769.
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Gabrielsson, Jonas. "Estimation of satellite orbits using ground based radar concept." Thesis, Umeå universitet, Institutionen för fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-185298.
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Today an abundance of objects are circulating in earth captured orbit. Monitoring these objects is of national security interest. One way to map any object in orbit is with their Keplerian elements. A method for estimating the Keplerian elements of a satellite orbit simulating a ground based radar station has been investigated. A frequency modulated continuous wave radar (FMCW) with a central transmitter antenna and a grid of receivers was modeled in MATLAB. The maximum likelihood estimator (MLE) was obtained to estimate the parameters from the received signal. The method takes advantage of the relations between the Cartesian position and velocity and the Keplerian elements to confine the search space. For a signal to noise ratio (SNR) of 10dB, the satellite was followed during a time period of 0.1s where the positions were found within average error of range: ±1.4m, azimuth: ±2.0·10−6 rad and elevation: ±8.4·10−7 rad. Using a linear approximation of the velocity the Keplerian elements were found within average error of i: ±0.0050 rad, Ω:±0.0050 rad, ω: ±0.0058 rad, a: ±2.60·105m, e:±0.0021 and ν: ±0.24 rad. A method to obtain more accurate estimates is proposed.
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Lee, Jaesang. "Vector-based ground surface and object representation using cameras." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024966.
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Czapla-Myers, Jeffrey. "Automated Ground-Based Methodology in Support of Vicarious Calibration." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195588.
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The Remote Sensing Group (RSG) at the University of Arizona performs the vicarious calibration of airborne and spaceborne sensors using ground-based measurements. Vicarious calibration is important because it is independent of the sensor and any onboard calibration system, but it requires that RSG personnel be present at a test site during the aircraft or satellite overpass. The ground-based data collection can be limited by poor weather, and also by the large travel distances from RSG's laboratory to the test sites.This dissertation presents an automated methodology that is used in support of vicarious calibration. The most important parameter measured during a vicarious calibration field campaign is the surface reflectance, and this work describes the method and instrumentation to obtain surface reflectance in the absence of RSG personnel. The instrumentation required to measure the surface and atmospheric parameters is discussed. The design and laboratory characterization of a nadir-viewing, multispectral radiometer is presented. Finally, results using this methodology are compared to those obtained using vicarious calibration, and also with the top-of-atmosphere radiance for one Terra MODIS, and two Aqua MODIS overpasses.
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Rana, Suman. "RISK-TARGETED GROUND MOTION FOR PERFORMANCE- BASED BRIDGE DESIGN." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2137.
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The seismic design maps on ASCE 7-05, International Building Code- 2006/2009, assumed uniform hazard ground motion with 2% probability of exceedance in 50 years for the entire conterminous U.S. But, Luco et al in 2007 pointed out that as uncertainties in collapse capacity exists in structures, an adjustment on uniform hazard ground motion was proposed to develop new seismic design maps. Thus, risk-targeted ground motion with 1% probability collapse in 50 years is adopted on ASCE 7-10. Even though these seismic design maps are developed for buildings, performance-based bridge design is done using same maps. Because significance difference lies on design procedure of buildings and bridges this thesis suggests some adjustment should be made on uncertainty in the collapse capacity(β) when using for bridge design. This research is done in 3 cities of U.S— San Francisco, New Madrid and New York. Hazard curve is drawn using 2008 version of USGS hazard maps and risk- targeted ground motion is calculated using equation given by Luco et al adjusting the uncertainty in collapse capacity(β) to be 0.9 for bridge design instead of 0.8 as used for buildings. The result is compared with existing result from ASCE 7-10, which uses β=0.6. The sample design response spectrum for site classes A, B, C and D is computed for all 3 cities using equations given in ASCE 7-10 for all β. The design response spectrum curves are analyzed to concluded that adjustment on uncertainty in collapse capacity should be done on ASCE 7-10 seismic design maps to be used for performance-based bridge design.
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Bell, Paul S. "Remote determination of bathymetric changes using ground based radar." Thesis, Bangor University, 2005. https://research.bangor.ac.uk/portal/en/theses/remote-determination-of-bathymetric-changes-using-ground-based-radar(eb303999-3681-4c95-8089-5bddf4d7c464).html.
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The determination of seabed bathymetry is a task commonly carried out by survey vessels using an echo sounder and satellite positioning systems. During the present study a method was developed to map the bathymetry of shallow water areas rapidly and remotely using radar image sequences of waves from two types of shore-based radar systems: an X-band marine radar (9.8 GHz) recording waves up to 2 km from the shore and a high resolution mm wave radar (77 GHz) with a range of approximately 200 m for measuring waves in the surf zone. The physical properties of the wave field were determined from the radar images. Using wave theory, these properties were then used to determine the local water depth. Following investigation of several wave theories, a dispersion equation that approximates the effects of both frequency and amplitude dispersion was found to be the most appropriate. The wavelengths of the waves imaged by the radar were mapped over a range of wave frequencies using a Fourier transform based algorithm for determining the wavelength of 2D waveforms in short lengths of data. The results were used with the selected depth inversion algorithm to infer the water depth matching the observed wave behaviour. Data from two sites were documented in detail: Faro in the Algarve region of Portugal, and Teignmouth in south west England. Radar data from these sites were processed to determine the bathymetry and the results compared with conventional surveys. The water depths derived from the short range mm wave radar data using the non-linear wave dispersion equation showed a mean offset of less than 0.1 m and the standard deviation of the scatter was of the order of 0.2 m. The water depths derived from the longer range X-band radar data again showed a mean offset of the order of 0.1 m and a slightly larger scatter standard deviation of 0.3 m for depths of up to 15 m. The water depths derived from the Teignmouth X-band radar data showed a similar pattern, with a mean offset of less than 0.1 m and a standard deviation of slightly over 0.2 m for water depths of up to 10 m. Radar data obtained in 1999 and 2003 from a tidal inlet in the barrier island system near Faro, Portugal were analysed to obtain bathymetric maps. Comparison of these two bathymetries showed the natural migration of the inlet and the associated bathymetric changes recorded by other researchers using conventional survey methods. In addition, the bathymetric changes evident in the radar derived bathymetries identified deposition to depths exceeding 0.5 m over a wide area of the ebb delta. Further, the data revealed extensive down-drift erosion to a depth of more than 1.5 m. These new observations showed that the balance between accretion and erosion plays an important role in the mechanisms driving inlet migration. This had not been documented previously owing to the practical difficulties of surveying the site by conventional methods. The changes in sediment volume estimated from the two sets of radar data suggest that more than 85% of the sediment supplied by longshore transport is being sequestered in the flood and ebb deltas, resulting in the erosion of the down-drift barrier island and enhanced rates of inlet migration. The techniques developed during this study are now firmly established for future use in coastal studies, and a number of projects are planned to include the use of X-band radar for this purpose.
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Gudmundson, Karl. "Ground Based Attitude Determination Using a SWIR Star Tracker." Thesis, Linköpings universitet, Reglerteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-158129.
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This work investigates the possibility of obtaining attitude estimates by capturing images of stars using a SWIR camera. Today, many autonomous systems rely on the measurements from a GPS to obtain accurate position and attitude estimates. However, the GPS signals are vulnerable to both jamming and spoofing, making any system reliant on only GPS signals insecure. To make the navigation systems more robust, other sensors can be added to acquire a multisensor system. One of these sensors might be a ground based SWIR star camera that is able to provide accurate attitude estimates. To investigate if this is possible, an experimental setup with a SWIR camera was placed at the office of FOI Linköping, where the camera in a rigid position has captured images of the sky. The SWIR camera possesses several advantages over a camera operating in the visual spectrum. For example, the background radiation is weaker and the transmission through the atmosphere is higher in certain wavelength bands. The images captured by the SWIR camera was provided to a star tracker software that has been developed. The star tracker software contains algorithms to detect stars, position them in the image at subpixel accuracy, match the stars to a star database and finally output an attitude based on the stars from the image and the identified stars in the database. To further improve the attitude estimates, an MEKF was applied. The results show that attitude estimates could be obtained consistently from late evenings to early mornings, when the sky was dark. However, this required that the weather conditions were good, i.e., a limited amount of clouds. When more clouds were present, no attitude estimates could be provided for a majority of the night. The SWIR camera was also compared to a camera operating in the visual spectrum when clouds were present, to see if the results were any different. With the camera settings applied in this work, the two cameras seemed to perform equally. The accuracy of the estimated attitudes is hard to validate, since no true attitude is available. However, the variance of the estimates was low, and the major differences in the attitude estimates over a night's measurements seemed to be a drift present in all angles. The maximum estimated error in declination during a night's measurements varied from about 40 to 60 arc seconds, depending on the data set. The maximum estimated error in right ascension varied between 200 and 2000 arc seconds, and the same metric in the roll estimate were about 100 to 2500 arc seconds. The reason for the drifts is assumed to be atmospheric effects not being accounted for, and astronomical effects moving the direction of the rotation axis of the earth, creating errors in the star positions given in the database.
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Van, Delst Paul F. "Ozone concentration profile retrieval from ground-based high-resolution thermal infrared spectra." Thesis, Curtin University, 1996. http://hdl.handle.net/20.500.11937/1887.
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Simulations of the Atmospheric Emitted Radiance Interferometer (AERI), a ground-based, high-resolution infrared detection system, are used to produce retrieved atmospheric ozone concentration profiles. A line-by-line transmittance model, FASCD3P, is used for the forward model and a maximum likelihood retrieval scheme is employed for the inverse model. An a priori data set consisting of 83 midlatitude winter ozone sondes is used to condition the inversion. Three iterations are required to reduce the radiance residuals to less than the instrument noise. The retrieval accuracy below 300mb is within 25% of truth. Above 300mb, variance within the a priori data is the dominant source of retrieval error. This is due to the number of retrieved layers (27) being higher than the amount of independent information present in the radiance spectra (approximately 4) so much of the retrieval information above 300mb comes from the a priori data.
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Amézaga, Adrià. "Design and implementation of an SDR-based multi-frequency ground-based SAR system." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/670326.
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Synthetic Aperture Radar (SAR) has proven a valuable tool in the monitoring of the Earth, either at a global or local scales. SAR is a coherent radar system able to image extended areas with high resolution, and finds applications in many areas such as forestry, agriculture, mining, structure inspection or security operations.
Although space-borne SAR systems can image extended areas, their main limitation is the long revisit times, which are not suitable for applications where the target experiments rapid changes, in the scale of minutes to few days. GBSAR systems have proven useful to fill this revisit time gap by imaging relatively small areas continuously, with extensions usually smaller than a few square kilometers. Ground Based SAR (GBSAR) systems have been used extensively for the monitoring of slope instability, and are a common tool in the mining sector.
The development of the GBSAR is relatively recent, and various developments have taken place since the 2000s, transitioning from the usage of Vector Network Analyzers (VNAs) to custom radar cores tailored for this application. This transition is accompanied by a reduction in cost, but at the same time is accompanied by a loss of operational flexibility. Specifically, most GBSAR sensors now operate at a single frequency, losing the value of the multi-band operation that VNAs provided.
This work is motivated by the idea that it is worth to use the value of multi-frequency GBSAR measurements, while maintaining a limited system cost. In order to implement a GBSAR with these characteristics, it is realized that Software Defined Radio (SDR) devices are a good option for fast and flexible implementation of broadband transceivers.
This thesis details the design and implementation process of an SDR-based Frequency Modulated Continuous Wave (FMCW) GBSAR system from the ground up, presenting the main issues related with the usage of the most common SDR analog architecture, the Zero-IF transceiver. The main problem is determined to be the behavior of spurs related to IQ imbalances of the analog transceiver with the FMCW demodulation process. Two effective techniques to overcome these issues, the Super Spatial Variant Apodization (SSVA) and the Short Time Fourier Transform (STFT) signal reconstruction techniques, are implemented and tested. The thesis also deals with the digital implementation of the signal generator and digital receiver, which are implemented on top of an RF Network-on-Chip (RFNoC) architecture in the SDR Field Programmable Gate Array (FPGA). Another important aspect of this work is the development of an radiofrequency front-end that extends the capabilities of the SDR, implementing filtering, amplification, leakage mitigation and up-conversion to X-band. Finally, a set of test campaigns is described, in which the operation of the system is verified and the value of multi-frequency GBSAR observations is shown.El radar d'obertura sintètica (SAR) ha demostrat ser una eina valuosa en el monitoratge de la Terra, sigui a escala global o local. El SAR és un sistema de radar coherent capaç d’obtenir imatges de zones extenses amb alta resolució i té aplicacions en moltes àrees com la silvicultura, l’agricultura, la mineria, la inspecció d’estructures o les operacions de seguretat. Tot i que els sistemes SAR embarcats en plataformes orbitals poden obtenir imatges d'àrees extenses, la seva principal limitació és el temps de revisita, que no són adequats per a aplicacions on l'objectiu experimenta canvis ràpids, en una escala de minuts a pocs dies. Els sistemes GBSAR han demostrat ser útils per omplir aquesta bretxa de temps, obtenint imatges d'àrees relativament petites de manera contínua, amb extensions generalment inferiors a uns pocs quilòmetres quadrats. Els sistemes SAR terrestres (GBSAR) s’han utilitzat àmpliament per al control de la inestabilitat de talussos i esllavissades i són una eina comuna al sector miner. El desenvolupament del GBSAR és relativament recent i s’han produït diversos desenvolupaments des de la dècada de 2000, passant de l’ús d’analitzadors de xarxes vectorials (VNA) a nuclis de radar personalitzats i adaptats a aquesta aplicació. Aquesta transició s’acompanya d’una reducció del cost, però al mateix temps d’una pèrdua de flexibilitat operativa. Concretament, la majoria dels sensors GBSAR funcionen a una única freqüència, perdent el valor de l’operació en múltiples bandes que proporcionaven els VNA. Aquesta tesi està motivada per la idea de recuperar el valor de les mesures GBSAR multifreqüència, mantenint un cost del sistema limitat. Per tal d’implementar un GBSAR amb aquestes característiques, s’adona que els dispositius de ràdio definida per software (SDR) són una bona opció per a la implementació ràpida i flexible dels transceptors de banda ampla. Aquesta tesi detalla el procés de disseny i implementació d’un sistema GBSAR d’ona contínua modulada en freqüència (FMCW) basat en la tecnologia SDR, presentant els principals problemes relacionats amb l’ús de l’arquitectura analògica de SDR més comuna, el transceptor Zero-IF. Es determina que el problema principal és el comportament dels espuris relacionats amb el balanç de les cadenes de fase i quadratura del transceptor analògic amb el procés de desmodulació FMCW. S’implementen i comproven dues tècniques efectives per minimitzar aquests problemes basades en la reconstrucció de la senyal contaminada per espuris: la tècnica anomenada Super Spatial Variant Apodization (SSVA) i una tècnica basada en la transformada de Fourier amb finestra (STFT). La tesi també tracta la implementació digital del generador de senyal i del receptor digital, que s’implementen sobre una arquitectura RF Network-on-Chip (RFNoC). Un altre aspecte important d’aquesta tesi és el desenvolupament d’un front-end de radiofreqüència que amplia les capacitats de la SDR, implementant filtratge, amplificació, millora de l'aïllament entre transmissió i recepció i conversió a banda X. Finalment, es descriu un conjunt de campanyes de prova en què es verifica el funcionament del sistema i es mostra el valor de les observacions GBSAR multifreqüència.
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Rahimi, Behrooz. "Ground Support and Reinforcement Design in Deep Underground Excavation Based on Ground Condition with Emphasis on Mining." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/76124.
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In this thesis, design of ground support system in deep underground mining is taken account into characterising ground conditions and presenting a new classification in deep and hard rocks. A new insight into the diagnosis of ground behaviour modes and identifying failure mechanism was presented. Also, a developed design methodology so-called CUED method (Comprehensive Underground Excavation Design) was proposed. According to this method, a procedure was defined for each step by the determining IPO(Input/processing/output) approach.
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Das, Satyaki. "Tools for Comparing ICON EUV Data with Different Ground Based and Space-based Proxies." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/90371.
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The ionosphere is the part of Earth's upper atmosphere, from about 60 km to 1,000 km altitude and contains ionized particles and plasma. In this region at about 150 kilometers above the surface of the earth starts the F region and it extends up to 500 kilometers. The Ionosphere is filled with tenuous gases and is a mixture of neutral and charged particles. These winds do not follow any flow pattern and changes with season, the day's heating and cooling, and incoming bursts of radiation from the sun. In order to study the behavior of these ions and understand this complicated region, NASA has developed the ICON mission. The satellite consists of four major instruments which are IVM, EUV, FUV and MIGHTI. This work is concentrated on the EUV instrument which measures the ionized oxygen densities in the F region of the Ionosphere. Different atmospheric model including the IRI and TIEGCM, along with data obtained from ground-based observations and the ICON FUV instrument will be compared to the ionized oxygen profile, NmF2, HmF2 and various other parameters that are obtained from the EUV. The tool developed for ICON EUV instrument is tested using SSULI data and it agrees with the IRI and TIEGCM model.Master of Science
The ionosphere is the part of Earth's upper atmosphere, from about 60 km to 1,000 km altitude and contains ionized particles and plasma. In this region at about 150 kilometers above the surface of the earth starts the F region and it extends up to 500 kilometers. The Ionosphere is filled with tenuous gases and is a mixture of neutral and charged particles. In order to study the behavior of these ions and understand this complicated region, NASA has developed the ICON mission. This work is concentrated on retrieving the data from EUV (Extreme Ultra Violet) instrument and compares the data with previously obtained data to check how consistent it is.
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Liu, Li. "Ground vehicle acoustic signal processing based on biological hearing models." College Park, Md. : University of Maryland, 1999. http://techreports.isr.umd.edu/reports/1999/MS%5F99-6.pdf.
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Thesis (M.S.) -- University of Maryland, College Park, 1999.Thesis research directed by Institute for Systems Research. "M.S. 99-6." Includes bibliographical references (leaves 75-78). Available also online as a PDF file via the World Wide Web.
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Shah, Syed Irtiza Ali. "Single camera based vision systems for ground and; aerial robots." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37143.
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Efficient and effective vision systems are proposed in this work for object detection for ground&aerial robots venturing into unknown environments with minimum vision aids, i.e. a single camera. The first problem attempted is that of object search and identification in a situation similar to a disaster site. Based on image analysis, typical pixel-based characteristics of a visual marker have been established to search for, using a block based search algorithm, along with a noise and interference filter. The proposed algorithm has been successfully utilized for the International Aerial Robotics competition 2009. The second problem deals with object detection for collision avoidance in 3D environments. It has been shown that a 3D model of the scene can be generated from 2D image information from a single camera flying through a very small arc of lateral flight around the object, without the need of capturing images from all sides. The forward flight simulations show that the depth extracted from forward motion is usable for large part of the image. After analyzing various constraints associated with this and other existing approaches, Motion Estimation has been proposed. Implementation of motion estimation on videos from onboard cameras resulted in various undesirable and noisy vectors. An in depth analysis of such vectors is presented and solutions are proposed and implemented, demonstrating desirable motion estimation for collision avoidance task.
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Eghtesad, Mohammad. "Dynamics-based linearization and control of an autonomous ground vehicle." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10116.
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Several aspects of dynamics based motion control of autonomous ground vehicles have been studied. For example kinematic and dynamic modelling of the vehicle, path and motion planning, path following and trajectory tracking, stabilization to a manifold and a to a desired position with specified orientation have been considered. Assuming the (ideal) rolling without slipping conditions for a wheel imposes the nonholonomic (non-integrable) constraints on the motion of the wheel and the vehicle. Nonholonomic systems are found not to be asymptotically stabilizable by a smooth state feedback laws. In this research, first, kinematics and Newtonian dynamics of a tricycle with front wheel steering and driving are developed and then using the concepts of Lagrange equations of the first kind, the dynamic models of the tricycle in the form of x = f(x,u) with torque inputs are derived. Nonlinear control theory and input-output feedback linearization as a systematic approach have been applied on these dynamic models of the vehicle. Cartesian space feedback linearization is utilized for trajectory tracking and asymptotic stabilization to a one dimensional manifold and simulation results are provided. Curvilinear space feedback linearization approach for asymptotic stabilization of two outputs with open-loop control of the third planar variable using a planned path between two end positions and orientations has been verified by simulations and implemented on an experimental setup. Internal dynamics of the system has been investigated, and its dimension, state variable and stability have been analysed.
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Aloi, Daniel Nicholas. "Electromagnetic analysis of ground multipath for satellite-based positioning systems." Ohio : Ohio University, 1996. http://www.ohiolink.edu/etd/view.cgi?ohiou1178816934.
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Walker, Richard J. "Development of the 200-μm photometer for ground-based astronomy." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/54542/.
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The thesis presented here describes the design and construction of a 200-um photometer, THUMPER, a seven-element array of stressed Ge:Ga photoconductors. The photometer has been designed to observe at the James Clerk Maxwell Telescope (JCMT) in conjunction with SCUBA, with an angular resolution of 14". A model for the expected atmospheric transmission at high-altitude, ground-based sites is developed. The model is validated through comparison with site-testing measurements of the atmosphere near to the 200-um window. It has been found that THUMPER will be able to undertake useful observations with levels of precipitable water vapour less than around 0.5 mm, occurring under the most favourable of weather conditions. The opportunities for THUMPER provided by the sites at Mauna Kea, Atacama and Antarctica are reviewed. Details concerning the manufacture and testing of stressed Ge:Ga photoconductors are presented. This includes work carried out on prototypes, followed by a description of the detectors used in the THUMPER arrays. The THUMPER detectors were tested individually and found to have values of detective quantum efficiency ranging from 6 to 12%. The basic design parameters for THUMPER are presented along with considerations for the commissioning of our instrument. In addition to plans for the integration of THUMPER at the JCMT, flux calculations have been presented indicating both Mars and Jupiter will provide sufficient fluxes for initial calibration.
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Cadeddu, Maria Paola. "Remote sensing of the atmosphere by ground-based microwave radiometry." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/461.
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Anderson, Sterling J. Ph D. Massachusetts Institute of Technology. "Constraint-based navigation for safe, shared control of ground vehicles." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79314.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 138-147).
Human error in machine operation is common and costly. This thesis introduces, develops, and experimentally demonstrates a new paradigm for shared-adaptive control of human-machine systems that mitigates the effects of human error without removing humans from the control loop. Motivated by observed human proclivity toward navigation in fields of safe travel rather than along specific trajectories, the planning and control framework developed in this thesis is rooted in the design and enforcement of constraints rather than the more traditional use of reference paths. Two constraint-planning methods are introduced. The first uses a constrained Delaunay triangulation of the environment to identify, cumulatively evaluate, and succinctly circumscribe the paths belonging to a particular homotopy with a set of semi autonomously enforceable constraints on the vehicle's position. The second identifies a desired homotopy by planning - and then laterally expanding - the optimal path that traverses it. Simulated results show both of these constraint-planning methods capable of improving the performance of one or multiple agents traversing an environment with obstacles. A method for predicting the threat posed to the vehicle given the current driver action, present state of the environment, and modeled vehicle dynamics is also presented. This threat assessment method, and the shared control approach it facilitates, are shown in simulation to prevent constraint violation or vehicular loss of control with minimal control intervention. Visual and haptic driver feedback mechanisms facilitated by this constraint-based control and threat-based intervention are also introduced. Finally, a large-scale, repeated measures study is presented to evaluate this control framework's effect on the performance, confidence, and cognitive workload of 20 drivers teleoperating an unmanned ground vehicle through an outdoor obstacle course. In 1,200 trials, the constraint-based framework developed in this thesis is shown to increase vehicle velocity by 26% while reducing the occurrence of collisions by 78%, improving driver reaction time to a secondary task by 8.7%, and increasing overall user confidence and sense of control by 44% and 12%, respectively. These performance improvements were realized with the autonomous controller usurping less than 43% of available vehicle control authority, on average.
by Sterling J. Anderson.
Ph.D.
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Steiner, Theodore J. III (Theodore Joseph). "Utility-based map reduction for ground and flight vehicle navigation." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98802.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 167-182).
Maps used for navigation often include a database of location descriptions for place-recognition (to enable localization or loop-closing), which permits bounded-error navigation performance. A standard localization system must describe the entire operational environment in its place-recognition database. A standard pose-graph-based simultaneous localization and mapping (SLAM) system adds a new place-recognition database entry for every new vehicle pose, which grows linearly and unbounded in time and thus becomes unsustainable. To address these issues, this thesis proposes a new map-reduction approach that pre-constructs a fixed-size place-recognition database amenable to the limited storage and processing resources of the vehicle by exploiting the high-level structure of the environment and vehicle motion. In particular, the thesis introduces the concept of location utility - which encapsulates the visitation probability of a location and its spatial distribution relative to nearby locations in the database - as a measure of the value of potential localization or loop-closure events to occur at that location. While finding the optimal reduced location database is NP-hard, an efficient greedy algorithm is developed to sort all the locations in a map based on their relative utility without access to sensor measurements or the vehicle trajectory. This enables predetermination of a generic, limited-size place-recognition database containing the N best locations in the environment. A street-map simulator using city-map data and a terrain relative navigation simulator using terrestrial rocket flight data are used to validate the approach and show that an accurate map and trajectory reconstruction (pose-graph) can be attained even when using a place-recognition database with only 1% of the entries of the corresponding full database.
by Theodore J. Steiner III.
Ph. D.
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Bento, Joao Paulo da Silva. "Research and development of ground-based transiting extrasolar planet projects." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/54441/.
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The search for exoplanets has gone from the realm of speculation to being one of the most prolific topics of modern astronomy in the space of just 20 years. In particular, the geometric alignment of transiting exoplanets provides the added opportunity to measure a host of properties of these systems, including studies of planetary atmospheres. The vast majority of known transiting exoplanets to date were found using dedicated ground-based surveys such as the SuperWASP project. Such enterprises comprise of multiple small telescopes designed to perform high-precision photometry over a wide field of view and rely on efficiently compensating for several noise contributions. An analysis of the sources of noise in the SuperWASP light curves was performed, focussing on systematic e↵ects fixed in detector space. A study of a set of detector maps produced from the average of the fractional residuals of the light curves in CCD coordinates has revealed that the current flat-fielding strategy is introducing a component of red noise into the light curves due to the wavelengthdependent nature of the CCDs. The possibility of using such maps as a basis for an additional decorrelation step in the software pipeline is discussed. The next phase in planetary discoveries from ground-based surveys consists of the search for smaller planets and those in longer orbits around their host stars. This process involves an observing strategy that focuses on intensive coverage of particular locations of the sky. We develop simulation software to aid the choice of observed fields for the SuperWASP and Next Generation Transit Survey (NGTS) projects in order to maximise the chances of finding planets at those locations. Moreover, this simulation can be used for comparative studies of the planet finding probability for several design choices and has been used to justify the necessity to commission the NGTS instrument at ESO’s Paranal Observatory in order to benefit from one of the World’s premier sites. The increasing number of known transiting planets has triggered a new phase of exoplanet exploration, in which the properties of the atmospheres of these planets are being explored using techniques such as transmission spectroscopy. This process consists of measuring an enhanced transit depth at particular wavelengths due to the presence of opacity sources in the atmospheres of exoplanets. We use the multiband photometer ULTRACAM to attempt a similar measurement via the technique of transmission photometry for the highly inflated planets WASP-15b and WASP- 17b. The data are found to be dominated by systematic errors and a detailed study of the possible sources is performed.
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Burkes, Darryl A. "GROUND SUPPORT FOR THE SPACE-BASED RANGE FLIGHT DEMONSTRATION 2." International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604565.
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ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, NevadaThe primary objective of the NASA Space-Based Range Demonstration and Certification program was to develop and demonstrate space-based range capabilities. The Flight Demonstration 2 flights at NASA Dryden Flight Research Center were conducted to support Range Safety (commanding and position reporting) and high-rate (5 Mbps) Range User (video and data) requirements. Required ground support infrastructure included a flight termination system computer, the ground-data distribution network to send range safety commands and receive range safety and range user telemetry data and video, and the ground processing systems at the Dryden Mission Control Center to process range safety and range user telemetry data and video.
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Daniau, Marc, and Philippe Millet. "IMPLEMENTATION OF CE83 FORMAT IN A GROUND-BASED TELEMETRY SYSTEM." International Foundation for Telemetering, 1992. http://hdl.handle.net/10150/608942.
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International Telemetering Conference Proceedings / October 26-29, 1992 / Town and Country Hotel and Convention Center, San Diego, CaliforniaDELTA 6000 System is a universal opened system for preprocessing, archival, realtime and offline analysis of telemetry data. The heterogeneous LAN architecture of DELTA 6000 comprises several front end ensuring the telemetry and high level realtime processing functions and several workstations for system control and display. The high communication level of DELTA 6000 enables an easy resource sharing as well as integration in customer environment. Easy operation through an efficient human interface and high versatility through the largest use of the most famous hardware and software industry standards are the major features of DELTA 6000. The more recent evolution of DELTA 6000 is the CE83 format realtime handling for use in European missiles programs.
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Taylor, Bruce A. "VME Based Ground Stations at Mcdonnell Douglas Aerospace Flight Test." International Foundation for Telemetering, 1995. http://hdl.handle.net/10150/611608.
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International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, NevadaThe ability to dynamically configure our ground stations to support a wide array of fighter/attack aircraft programs has lead McDonnell Douglas Aerospace (MDA) to seek alternatives to commercially available ground stations. Cost effectiveness and fast response time to these widely varying needs is paramount to staying competitive in today's current defense environment. VME (Versa Modular European) architecture has provided a platform that fulfills these requirements while requiring a minimum of in house designs which can be expensive and time consuming to implement. MDA is now in its third generation of VME based ground systems. These systems are highly extensible due to their reliance on software and programmable hardware systems and are inexpensive due to their use of commercial grade VME cards. This paper describes the current generation TM/Quicklook Ground Station and the Data Editor (Preprocessor) Station and it also provides a perspective of how the designers solved some common problems associated with VME architecture. These stations are now in use at MDA test sights in St. Louis, Patuxent River NAWC, Edwards AFB, and Eglin AFB.
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Fohring, Dora. "The effect of scintillation on ground-based exoplanet transit photometry." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10954/.
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In this thesis, the effect of scintillation arising from atmospheric optical turbulence on exoplanet transit and secondary eclipse photometry is examined. Atmospheric scintillation arises from the propagation of phase aberrations resulting from wavefront perturbations due to optical turbulence high in the atmosphere. Scintillation causes intensity variations of astronomical targets, which is a problem in exoplanet transit photometry, where the measurement of a decrease in brightness of 1% or less is required. For this reason, ground-based telescopes have inferior photometric precision compared to their space-based counterparts, despite having the advantage of a reduced cost. In contrast with previous work on the detection limits of fast photometry, which is obtained for an atmosphere averaged over time, the actual scintillation noise can vary considerably from night to night depending on the magnitude of the high-altitude turbulence. From simulation of turbulent layers, the regimes where scintillation is the dominant source of noise on photometry are presented. These are shown to be in good agreement with the analytical, layer based, equations for scintillation. Through Bayesian analysis, the relationship between the errors on the light and the uncertainties on the astrophysical parameters are examined. The errors on the light curve arising from scintillation linearly increase the scatter on the astrophysical parameters with a gradient in the range of 0.68 -0.80. The noise due to the photometry aperture is investigated. It is found that for short exposure in times in good seeing, speckle noise contributes to noise in photometry for aperture sizes of up to approximately 2.3xFWHM. The results from simultaneous turbulence profiling and time-series photometry are presented. It is found that turbulence profiling can be used to accurately predict the amount of scintillation noise present in photometric observations. An investigation of the secondary eclipse of WASP-12b on the William Herschel Telescope (WHT) is performed, resulting in a high quality z’-band light curve for WASP-12b consistent with a carbon-rich model and with no evidence for strong thermal inversion.