Water surface monitoring using GNSS-R opportunity signals

Water surface monitoring using the IPT technique for geophysical parameter retrieval.[ANGLÈS] This Master Thesis follows the future research lines recommended in Dr. Nereida Rodríguez Álvarez Ph.D Thesis dissertation. It is based on the application of the Interference Pattern Technique (IPT) on dynamic surfaces trying to monitor the water-level. The Global Navigation Satellite Systems (GNSS) signals are presented and then the Delay Doppler Map (DDM) technique and the IPT technique are introduced in detail. The basic equations are presented to fully understand the concepts. Both techniques can be applied today to Earth observation to retrieve geophysical parameters of the surface, such as the soil moisture, the topography and the wind speed. Then, the instrument that implements the IPT technique is described: it is the Soil Moisture Interference pattern technique GNSS-R Observations at L-band (SMIGOL) reflectometer. SMIGOL is an autonomous instrument consisting of a patch antenna with a symmetric pattern, a commercial GPS receiver, a GPS amplifier, a datalogger, a microcontroller, and a well-tailored power supply system containing batteries, solar panels, a buck boost power supply, and a battery charger. Some of the applications developed in the remote sensing laboratory (RSLab) using the IPT are presented, including soil moisture, vegetation height, water surface monitoring on reservoirs and topography. All these applications are supported with a critical analysis, and with the results of different field campaigns performed to validate the algorithms developed. Finally, a very detailed analysis of a field campaign performed in Vilanova i la Geltrú, Catalunya, Spain, to see how the IPT performs over dynamic surfaces is shown. All the intermediate steps of the signal processing are explained. From this campaign two different conclusions result; water-level monitoring cannot be performed under the same hypotheses as in reservoirs, and; the high dynamics of the water appear as a noise in the interference patterns which is correlated to the wind speed. An empirical formula relating the IPT observables and the wind speed is derived.[CASTELLÀ] Esta Tesis de Máster sigue las líneas futuras de investigación recomendadas en la Tésis doctoral de Dra. Nereida Rodríguez Álvarez. Se basa en la aplicación de la técnica patrón de interferencias (IPT) sobre superficies dinámicas para monitorizar el nivel del agua. Las señales los Sistemas Globales de Navegación por Satélite (GNSS) son presentadas para, consecuentemente, introducir la técnica Delay Doppler Map (DDM) y la técnica de IPT que se presenta en detalle. Se muestran también las ecuaciones básicas para comprender plenamente los conceptos. Ambas técnicas se pueden aplicar a día de hoy para la observación de la Tierra para recuperar parámetros geofísicos de la superficie, tales como la humedad del suelo, la topografía y la velocidad del viento. El instrumento que aplica la técnica de IPT se describe: es el reflectómetro Soil Moisture Interference pattern technique GNSS-R Observations at L-band (SMIGOL). SMIGOL es un instrumento autónomo que consta de una antena parche con un diagrama de radiación simétrico, un receptor GPS comercial, un amplificador de GPS, un datalogger, un microcontrolador y un sistema de alimentación bien confeccionado que contiene baterías, paneles solares, una fuente de alimentación conmutada, y un cargador de baterías. Algunas de las aplicaciones desarrolladas en el Laboratorio de Teledetección (RSLab) usando la IPT se presentan, incluyendo la humedad del suelo, altura de la vegetación, la monitorización del nivel de agua en embalses y la topografía. Todas estas aplicaciones son analizadas críticamente, junto con los resultados de diferentes campañas de medida realizadas para validar los algoritmos previamente desarrollados. Por último, se muestra un análisis muy detallado de una campaña de medida realizada en Vilanova i la Geltrú, Catalunya, España, para ver cómo la IPT funciona sobre superficies dinámicas. Se muestran detalladamente todos los pasos intermedios del procesado de los datos. De esta campaña de medidas se obtienen dos conclusiones distintas; la monitorización del nivel de agua sobre superficies dinámicas no puede realizarse bajo las mismas hipótesis que en el caso de los embalses, y; la alta dinámica del mar aparece en forma de ruido en los patrones de interferencia y dicho ruido está correlado con la velocidad del viento. Se deriva una fórmula empírica sobre las características observables del IPT y la velocidad del viento.[CATALÀ] Aquesta Tesi de Màster segueix les línies futures de recerca recomanades en la Tesi doctoral de Dra Nereida Rodríguez Álvarez. Es basa en l'aplicació de la tècnica patró d'interferències (IPT) sobre superfícies dinàmiques per monitoritzar el nivell de l'aigua. Els senyals dels Sistemes Globals de Navegació per Satèl lit (GNSS) són presentats per, conseqüentment, introduir la tècnica Delay Doppler Map (DDM) i la tècnica d'IPT que es presenta en detall. Es mostren també les equacions bàsiques per a comprendre plenament els conceptes. Ambdues tècniques es poden aplicar a dia d'avui per a l'observació de la Terra per recuperar paràmetres geofísics de la superfície, com ara la humitat del sòl, la topografia i la velocitat del vent. L'instrument que aplica la tècnica d'IPT es descriu: és el reflectòmetre Soil Moisture Interference pattern technique GNSS-R Observations at L-band (SMIGOL). SMIGOL és un instrument autònom que consta d'una antena impresa amb un diagrama de radiació simètric, un receptor GPS comercial, un amplificador de GPS, un datalogger, un microcontrolador i un sistema d'alimentació ben confeccionat que conté bateries, panells solars, una font de alimentació commutada, i un carregador de bateries. Algunes de les aplicacions desenvolupades en el Laboratori de Teledetecció (RSLAB) usant la IPT es presenten, incloent la humitat del sòl, alçada de la vegetació, la monitorització del nivell d'aigua en embassaments i la topografia. Totes aquestes aplicacions són analitzades críticament, juntament amb els resultats de diferents campanyes de mesura realitzades per validar els algorismes prèviament desenvolupats. Finalment, es mostra una anàlisi molt detallat d'una campanya de mesures realitzada a Vilanova i la Geltrú, Catalunya, Espanya, per veure com la IPT funciona sobre superfícies dinàmiques. Es mostren detalladament tots els passos intermedis del processat de les dades. D'aquesta campanya de mesures s'obtenen dues conclusions diferents: la monitorització del nivell d'aigua sobre superfícies dinàmiques no pot realitzar sota les mateixes hipòtesis que en el cas dels embassaments, i; l'alta dinàmica del mar apareix en forma de soroll en els patrons d'interferència i aquest soroll està correlat amb la velocitat del vent. Es deriva una fórmula empírica sobre les característiques observables de la IPT i la velocitat del vent

The NASA Geodynamics Program: An overview

This NASA Geodynamics Program overview collectively examines the history, scientific basis, status, and results of the NASA Program and outlines plans for the next five to eight years. It is intended as an informative nontechnical discussion of geodynamics research

Geodesy: A look to the future

The report deals with the current and future uses of contemporary geodetic data and poses some questions and possibilities for the future. It is anticipated that the document will generate interest in present and future geodetic data for the solution of problems in Earth, ocean, and atmospheric sciences

Localization Precise in Urban Area

Nowadays, stand-alone Global Navigation Satellite System (GNSS) positioning accuracy is not sufficient for a growing number of land users. Sub-meter or even centimeter accuracy is becoming more and more crucial in many applications. Especially for navigating rovers in the urban environment, final positioning accuracy can be worse as the dramatically lack and contaminations of GNSS measurements. To achieve a more accurate positioning, the GNSS carrier phase measurements appear mandatory. These measurements have a tracking error more precise by a factor of a hundred than the usual code pseudorange measurements. However, they are also less robust and include a so-called integer ambiguity that prevents them to be used directly for positioning. While carrier phase measurements are widely used in applications located in open environments, this thesis focuses on trying to use them in a much more challenging urban environment. To do so, Real Time-Kinematic (RTK) methodology is used, which is taking advantage on the spatially correlated property of most code and carrier phase measurements errors. Besides, the thesis also tries to take advantage of a dual GNSS constellation, GPS and GLONASS, to strengthen the position solution and the reliable use of carrier phase measurements. Finally, to make up the disadvantages of GNSS in urban areas, a low-cost MEMS is also integrated to the final solution. Regarding the use of carrier phase measurements, a modified version of Partial Integer Ambiguity Resolution (Partial-IAR) is proposed to convert as reliably as possible carrier phase measurements into absolute pseudoranges. Moreover, carrier phase Cycle Slip (CS) being quite frequent in urban areas, thus creating discontinuities of the measured carrier phases, a new detection and repair mechanism of CSs is proposed to continuously benefit from the high precision of carrier phases. Finally, tests based on real data collected around Toulouse are used to test the performance of the whole methodology

Contributions to the determination of electromagnetic bias in Gnss-R altimetry

In this Ph. D. dissertation the electromagnetic bias in GNSS-R (Global Navigation Satellite Systems Reflectometry) altimetry has been studied. GNSS-R altimetry is a new type of system that uses navigation signals as signals of opportunity for Earth observation. The electromagnetic bias has been a topic of research for several decades in conventional radar altimetry, typically at C and Ku bands, and pointing in the nadir direction, but it is a new subject in altimetry GNSS-R. Previous studies on the electromagnetic bias have been first reviewed: the Weakly Non-Linear theory (WNL), the Modulation Transfer Function (MTF), and a combination of both models. After a brief study of both the WNL and the MTF, a combined method is selected, simulated and validated at Ku and C bands, and then extrapolated at L band, the band of the GNSS signals. Then, the EM bias is studied in the time domain and it is characterized using statistical descriptors. Finally, the impact of natural phenomena such as rain, waves and currents in the electromagnetic bias is calculated. In conclusion, this dissertation has demonstrated that the electromagnetic bias is not only a function of the wind speed (or waves), but also a function of both the incidence and azimuth angles. The study in the time domain has been shown that it exhibits a non-linear behavior. Moreover, heavy rains decrease the electromagnetic bias, as they damp the waves, while sea currents in the opposite direction of the wind speed increase the electromagnetic bias, because they increase the surface "roughness", while currents with the same direction of the wind, reduce itEn esta tesis doctoral se estudia el sesgo electromagnético en altimetría GNSS-R (Global Navigation Satellite Systems Reflectometry). La altimetría GNSS-R es un nuevo tipo de sistema que utiliza las señales de navegación como señales de oportunidad para la observación de la tierra. El sesgo electromagnético ha sido un tema de investigación durante varias décadas en altimetría radar convencional utilizando típicamente las bandas C y Ku, y apuntando en la dirección nadir, pero es un tema novedoso en altimetría GNSS-R. En primer lugar se revisan los estudios previos sobre el sesgo electromagnético: la Weakly Non-Linear theory (WNL), la Modulation Transfer Function (MTF), y modelos combinados de ambos. Después de un breve estudio tanto de la WNL como de la MTF, se selecciona un modelo combinado, se simula, y valida en las bandas C y Ku, y luego es extrapolado a la banda L, la banda de las señales de los GNSS. En segundo lugar, se estudia el sesgo electromagnético en el dominio del tiempo y es caracterizado utilizando descriptores estadísticos. Por último, se calcula el impacto de los fenómenos naturales como la lluvia, el oleaje y las corrientes en el sesgo electromagnético . En conclusión, esta tesis doctoral ha demostrado que el sesgo electromagnético no es sólo una función de la velocidad del viento (o del oleaje), sino que también es una función tanto del ángulo de incidencia, como del ángulo de acimut. El estudio en el dominio del tiempo ha demostrado que tiene un comportamiento no lineal. Por otra parte, las fuertes lluvias disminuyen el sesgo electromagnético, pues amortiguan las olas, mientras que las corrientes con dirección opuesta al viento aumentan el sesgo electromagnético, pues aumentan la "rugosidad" superficial, mientras que la corriente tiene la misma dirección de la velocidad del viento, lo reduce

The determination of subtle deformation signals using a permanent CGPS network in the Aegean

Geophysical motions can occur over a broad temporal spectrum, from high frequency seismic movements to very long period tectonic deformation. The Aegean region is tectonically one of the most active areas on Earth. There have, over the past 15 years, been a range of campaign style GPS studies which have looked to increase our knowledge of the area and better define the geodynamic processes involved. In 2002 the Center for the Observation and Modelling of Earthquakes and Tectonics (COMET) established a network of continuously operating GPS receivers (CGPS) throughout the region in order to add to the knowledge gained from previous studies. This thesis focuses on which tectonic motions can be observed using the COMET continuous GPS network. Approaches for the precise analytical estimation of subtle tectonic motion are presented. Daily coordinate estimates of COMET sites and a number of ITRF (International Terrestrial Reference Frame) sites around Europe were calculated using a precise point positioning strategy and ambiguity resolution using NASA’s GIPSY – OASIS II processing software and IGS (International GPS Service) precise products. Time series produced showed post fit standard deviations of 2-3 mm in the horizontal and 6-8 mm in the vertical. Significant annual periodic variation is observed in the time series. The coordinate time series studies were further refined using a selection of filters. Firstly, gross and sigma filters were applied to remove outliers, the data then had a range of regional filters applied looking to best define and remove the common mode error in the area. These filters produced mixed results with time series improvement occurring on a site by site basis. In some cases noise was reduced by a factor of 2 whilst in other cases there was little or no improvement. This combined with a lack of knowledge of the individual site movements led to the use of a filtered baseline method, whereby common mode error was removed purely on a site by site basis. This method revealed expansion across the Hellenic arc of the order of a few millimetres per year and sub millimetre north-south compaction behind the arc. It also revealed first evidence of transient motion at a number of sites parallel to the Hellenic arc. The transient signals occurred every 12 months ±1.5 and lasting for 40 – 100 days. These signals were not so much a reversal of tectonic motion akin to the silent earthquakes observed in Cascadia, Japan and Mexico, instead they appeared more as a pause in the otherwise consistent movement of the Aegean microplate overriding the subducting African lithosphere. In addition to the observed tectonic signals, the effects and implications of the two post processing strategies are analysed and discussed. Higher temporal frequency positioning is carried out on seismic events (Mw 6.7 earthquake Kithera, Mw 8.1 and Mw 6.7 earthquakes, Macquarie island) using instantaneous positioning followed by “sidereal filtering” whereby integer-cycle phase ambiguities are resolved using only single epochs of dual frequency phase and pseudorange data. These positions are then siderealy stacked to reduce the effects of geometry related error. The technique reduces geometry related noise by a factor ≈2 using epoch by epoch 30 second data. The feasibility of the technique for observing pre, co and post seismic signals is demonstrated. A visualisation tool was developed to allow the simultaneous observation of the tectonic motion of a CGPS network data over any spatial and temporal regimes

Solid Earth science in the 1990s. Volume 3: Measurement techniques and technology

Reports are contained from the NASA Workshop on Solid Earth Science in the 1990s. The techniques and technologies needed to address the program objectives are discussed. The Measurement Technique and Technology Panel identified (1) candidate measurement systems for each of the measurements required for the Solid Earth Science Program that would fall under the NASA purview; (2) the capabilities and limitations of each technique; and (3) the developments necessary for each technique to meet the science panel requirements. In nearly all cases, current technology or a development path with existing technology was identified as capable of meeting the requirements of the science panels. These technologies and development paths are discussed

Field-based measurement of hydrodynamics associated with engineered in-channel structures: the example of fish pass assessment

The construction of fish passes has been a longstanding measure to improve river ecosystem status by ensuring the passability of weirs, dams and other in- channel structures for migratory fish. Many fish passes have a low biological effectiveness because of unsuitable hydrodynamic conditions hindering fish to rapidly detect the pass entrance. There has been a need for techniques to quantify the hydrodynamics surrounding fish pass entrances in order to identify those passes that require enhancement and to improve the design of new passes. This PhD thesis presents the development of a methodology for the rapid, spatially continuous quantification of near-pass hydrodynamics in the field. The methodology involves moving-vessel Acoustic Doppler Current Profiler (ADCP) measurements in order to quantify the 3-dimensional water velocity distribution around fish pass entrances. The approach presented in this thesis is novel because it integrates a set of techniques to make ADCP data robust against errors associated with the environmental conditions near engineered in-channel structures. These techniques provide solutions to (i) ADCP compass errors from magnetic interference, (ii) bias in water velocity data caused by spatial flow heterogeneity, (iii) the accurate ADCP positioning in locales with constrained line of sight to navigation satellites, and (iv) the accurate and cost-effective sensor deployment following pre-defined sampling strategies. The effectiveness and transferability of the methodology were evaluated at three fish pass sites covering conditions of low, medium and high discharge. The methodology outputs enabled a detailed quantitative characterisation of the fish pass attraction flow and its interaction with other hydrodynamic features. The outputs are suitable to formulate novel indicators of hydrodynamic fish pass attractiveness and they revealed the need to refine traditional fish pass design guidelines

Experimental evaluation of a mixer-ejector hydrokinetic turbine at two open-water test sites and in a tow tank

For marine hydrokinetic energy to become viable it is essential to develop energy conversion devices that extract energy with high efficiency, and to field-test them in an environment similar to the one in which they are designed to eventually operate. FloDesign Inc., with FloDesign Wind Turbine Corp., developed a Mixer-Ejector Hydrokinetic Turbine (MEHT) that encloses the turbine in a specially designed shroud to increase mass flow through the turbine rotor. A scaled version of this turbine was evaluated experimentally at two open-water tidal energy test sites, and in a tow tank. State-of-the-art instrumentation was used to measure free stream and wake velocities, turbine power extraction, test platform loadings and platform motion induced by sea state. The MEHT was able to generate power from tidal currents over a wide range of conditions, with low-velocity start-up. The decay of the wake velocity deficit was found to improve with increasing free stream turbulence