Contribucions a l'anàlisi automàtica de grans volums de dades

Aquesta tesi és fonamentalment un estudi sobre la recerca d'automatismes en diferents algorismes aplicats a la ciència de la informació geogràfica. Els treballs que la formen tenen un important objectiu comú: aconseguir la màxima qualitat possible dels resultats obtinguts en substituir el mètode habitual (manual) en l'anàlisi de grans volums de dades pel corresponent mètode automàtic, que mostra diversos avantatges respecte el primer, i en el qual tenen un paper rellevant les metadades, és a dir, la informació sobre dades, objectes o recursos.Esta tesis es fundamentalmente un estudio sobre la búsqueda de automatismos en diferentes algoritmos aplicados a la ciencia de la información geográfica. Los trabajos que la forman tienen un importante objetivo común: conseguir la máxima calidad posible de los resultados obtenidos al sustituir el método habitual (manual) en el análisis de grandes volúmenes de datos por el correspondiente método automático, que muestra varias ventajas respecto al primero, y en el que tienen un papel relevante los metadatos, es decir, la información sobre datos, objetos o recursos.This thesis is basically a study of the search for automatisms in different algorithms applied to Geographical Information Science. The works that form the thesis have an important common goal: to obtain the highest possible quality in results when replacing the usual (manual) method in the analysis of large volumes of data for the corresponding automatic method. This method shows several advantages over the former and in which metadata, i.e., information about data objects or resources, play an important role

RiBaSE : a pilot for testing the OGC web services integration of water-related information and models

The design of an interoperability experiment to demonstrate how current ICT-based tools and water data can work in combination with geospatial web services is presented. This solution is being tested in three transboundary river basins: Scheldt, Maritsa and Severn. The purpose of this experiment is to assess the effectiveness of OGC standards for describing status and dynamics of surface water in river basins, to demonstrate their applicability and finally to increase awareness of emerging hydrological standards as WaterML 2.0. Also, this pilot will help in identifying potential gaps in OGC standards in water domain applications, applied to a flooding scenario in present work

A provenance metadata model integrating ISO geospatial lineage and the OGC WPS : conceptual model and implementation

Nowadays, there are still some gaps in the description of provenance metadata. These gaps prevent the capture of comprehensive provenance, useful for reuse and reproducibility. In addition, the lack of automated tools for capturing provenance hinders the broad generation and compilation of provenance information. This work presents a provenance engine (PE) that captures and represents provenance information using a combination of the Web Processing Service (WPS) standard and the ISO 19115 geospatial lineage model. The PE, developed within the MiraMon GIS & RS software, automatically records detailed information about sources and processes. The PE also includes a metadata editor that shows a graphical representation of the provenance and allows users to complement provenance information by adding missing processes or deleting redundant process steps or sources, thus building a consistent geospatial workflow. One use case is presented to demonstrate the usefulness and effectiveness of the PE: the generation of a radiometric pseudo-invariant areas bench for the Iberian Peninsula. This remote-sensing use case shows how provenance can be automatically captured, also in a non-sequential complex flow, and its essential role in the automation and replication tasks in work with very large amounts of geospatial data

Generación de un banco de áreas de reflectividad pseudoinvariante para la Península Ibérica mediante imágenes MODIS

La reflectividad derivada de imágenes satelitales sigue generalmente el ciclo fenológico de las cubiertas presentes en el territorio. A pesar de ello, es posible encontrar zonas donde la reflectividad es prácticamente invariante. Estas áreas definidas como pseudoinvariantes (API) permiten comparar y calibrar imágenes provenientes de distintos sensores y procesar series temporales con una elevada coherencia. Se presenta un nuevo método automático (especialmente útil en entornos Big Data) para seleccionar API a partir del producto diario MOD09GA derivado de imágenes Terra-MODIS, utilizando una serie temporal de 14 años y las bandas del espectro solar (visible, infrarrojo cercano y de onda corta) con una resolución espacial de 500 m. Dicha metodología consta de dos etapas de filtrado, una primera que evalúa la calidad de las imágenes de la serie mediante técnicas geoestadísticas, seleccionando las mejores, y una segunda que define umbrales específicos para cada banda espectral, en función de la dispersión que presentan los datos en la selección previa de imágenes. La aplicación de este método sobre ámbitos de características topográficas y estructura de paisaje diferenciados en la Península Ibérica ha permitido la obtención de más de 12 000 API en una superficie asimilable a 9 escenas Landsat (WRS-2). Los resultados muestran que la metodología aplicada contempla la adecuada distribución tanto interanual como intraanual de las imágenes, dando lugar a API que abarcan una amplia variedad de cubiertas con reflectividades diversas, ubicadas principalmente en zonas boscosas o seminaturales (77%),zonas agrícolas (21 %), así como en otros tipos de cubiertas no vegetales

Metodología para el análisis de accesibilidad a los recursos sanitarios : el caso de Catalunya

En la planificación de servicios públicos, como los servicios sanitarios, resulta útil poder disponer de técnicas objetivas para el análisis y la cuantificación de su adecuación a la distribución de la población en el territorio. Con este objetivo, y con la colaboración entre el Departamento de Salud de la Generalitat de Cataluña, y el Departamento de Geografía y el Centro de Investigación Ecológica y Aplicaciones Forestales (CREAF) de la UAB, se llevó a cabo, entre los años 2007 y 2008, un estudio de la accesibilidad a los centros sanitarios públicos de Cataluña, mediante la utilización de herramientas de cálculo de rutas óptimas, integradas en un SIG. Los resultados ponen de manifiesto el interesante potencial de la metodología utilizada en la planificación territorial de los servicios sanitarios y los principales puntos a mejorar en términos de accesibilidad de la población a los recursos sanitarios.In the planning of public services such as health services, it is useful to have techniques for objective analysis and quantification of its suitability to the population distribution in the territory. With this purpose, and the collaboration between the Department of Health of the Generalitat of Catalonia, and the Department of Geography and the Center for Ecological Research and Forestry Applications (CREAF) at UAB, a study of accessibility to public health centers of Catalonia, through the use of tools for optimal routing, integrated into a GIS, was carried out during the years 2007 and 2008. The results show the interesting potential of the methodology used in the planning of health services and key points to improve in terms of accessibility of people to health resources

Estudio del estándar WaterML

Altres ajuts: Máster en Teledetección y SIG en la Universitat Autònoma de BarcelonaLos estándares para la información geoespacial distribuida pueden ser de propósito general o particulares de un dominio. Algunos dominios han avanzado más que otros en la estandarización y en la interoperabilidad como por ejemplo el dominio Meteorológico-Climático o el Hidrológico. El colectivo de Hidrología detectó la necesidad del estándar WaterML, el cual ayuda a la óptima gestión de los recursos del agua. En términos generales, WaterML es un estándar que define un modelo de datos para la representación de las observaciones hidrológicas, con la intención de permitir el intercambio de este conjunto de datos a través de sistemas de información. Está basado en dos estándares: Geographic Markup Language (GML) y Observations and Measurements (O&M). WaterML en su versión 2.0 fue desarrollado por Open Geospatial Consortium (OGC), fue aprobado a mediados del 2012 y finalmente publicado a inicios del 2014. A pesar de ser un estándar emergente, diversas instituciones gubernamentales y no gubernamentales han considerado útil estandarizar la información sobre sus series temporales de datos hidrológicos y además publicarlas en la web. Este trabajo revisa y cuantifica el nivel de uso de WaterML en las aplicaciones hidrológicas actuales y sitúa a WaterML en la arquitectura del conjunto de los estándares OGC

Improving mean minimum and maximum month-to-month air temperature surfaces using satellite-derived land surface temperature

Month-to-month air temperature (T) surfaces are increasingly demanded to feed quantitative models related to a wide range of fields, such as hydrology, ecology or climate change studies. Geostatistical interpolation techniques provide such continuous and objective surfaces of climate variables, while the use of remote sensing data may improve the estimates, especially when temporal resolution is detailed enough. The main goal of this study is to propose an empirical methodology for improving the month-to-month T mapping (minimum and maximum) using satellite land surface temperatures (LST) besides of meteorological data and geographic information. The methodology consists on multiple regression analysis combined with the spatial interpolation of residual errors using the inverse distance weighting. A leave-one-out cross-validation procedure has been included in order to compare predicted with observed values. Different operational daytime and nighttime LST products corresponding to the four months more characteristic of the seasonal dynamics of a Mediterranean climate have been considered for a thirteen-year period. The results can be considered operational given the feasibility of the models employed (linear dependence on predictors that are nowadays easily available), the robustness of the leave-one-out cross-validation procedure and the improvement in accuracy achieved when compared to classical T modeling results. Unlike what is considered by most studies, it is shown that nighttime LST provides a good proxy not only for minimum T, but also for maximum T. The improvement achieved by the inclusion of remote sensing LST products was higher for minimum T (up to 0.35 K on December), especially over forests and rugged lands. Results are really encouraging, as there are generally few meteorological stations in zones with these characteristics, clearly showing the usefulness of remote sensing to improve information about areas that are difficult to access or simply with a poor availability of conventional meteorological data

The role of recent (1985-2014) patterns of land abandonment and environmental factors in the establishment and growth of secondary forests in the Iberian Peninsula

Farmland abandonment has been a widespread land-use change in the Iberian Peninsula since the second half of the 20th century, leading to the establishment of secondary forests across the region. In this study, we aimed to address changes in the recent (1985-2014) emergence patterns of these forests and examine how environmental factors affected their growth by considering differences in leaf-habit types. We used a combination of Landsat-derived land-cover maps and above-ground biomass (AGB) maps from the European Space Agency to assess the secondary forest establishment and growth, respectively, in the study region. We also obtained a set of topographic, climatic and landscape variables from diverse GIS layers and used them for determining changes over time in the environmental drivers of forest establishment and AGB using general linear models. The results highlight that secondary forest cover was still increasing in the Iberian Peninsula at a rate above the European average. Yet, they also indicate a directional change in the emergence of secondary forests towards lower and less steep regions with higher water availability (mean rainfall and SPEI) and less forest cover but are subjected to greater drought events. In addition, these environmental factors differentially affect the growth of forests with different leaf-habit types: i.e., needleleaf secondary forests being less favoured by high temperature and precipitation, and broad-leaf deciduous forests being most negatively affected by drought. Finally, these spatial patterns of forest emergence and the contrasting responses of forest leaf-habits to environmental factors explained the major development of broadleaf evergreen compared to broadleaf deciduous forests and, especially, needleleaf secondary forests. These results will improve the knowledge of forest dynamics that have occurred in the Iberian Peninsula in recent decades and provide an essential tool for understanding the potential effects of climate warming on secondary forest growth

The role of recent (1985-2014) patterns of land abandonment and environmental factors in the establishment and growth of secondary forests in the Iberian Peninsula

Farmland abandonment has been a widespread land-use change in the Iberian Peninsula since the second half of the 20th century, leading to the establishment of secondary forests across the region. In this study, we aimed to address changes in the recent (1985-2014) emergence patterns of these forests and examine how environmental factors affected their growth by considering differences in leaf-habit types. We used a combination of Landsat-derived land-cover maps and above-ground biomass (AGB) maps from the European Space Agency to assess the secondary forest establishment and growth, respectively, in the study region. We also obtained a set of topographic, climatic and landscape variables from diverse GIS layers and used them for determining changes over time in the environmental drivers of forest establishment and AGB using general linear models. The results highlight that secondary forest cover was still increasing in the Iberian Peninsula at a rate above the European average. Yet, they also indicate a directional change in the emergence of secondary forests towards lower and less steep regions with higher water availability (mean rainfall and SPEI) and less forest cover but are subjected to greater drought events. In addition, these environmental factors differentially affect the growth of forests with different leaf-habit types: i.e., needleleaf secondary forests being less favoured by high temperature and precipitation, and broad-leaf deciduous forests being most negatively affected by drought. Finally, these spatial patterns of forest emergence and the contrasting responses of forest leaf-habits to environmental factors explained the major development of broadleaf evergreen compared to broadleaf deciduous forests and, especially, needleleaf secondary forests. These results will improve the knowledge of forest dynamics that have occurred in the Iberian Peninsula in recent decades and provide an essential tool for understanding the potential effects of climate warming on secondary forest growth

Solució paral·lelitzada d'interpolació kriging amb ajust automatitzat del variograma

El principal objectiu d'aquest treball és proporcionar una metodologia per a reduir el temps de càlcul del mètode d'interpolació kriging sense pèrdua de la qualitat del model resultat. La solució adoptada ha estat la paral·lelització de l'algorisme mitjançant MPI sobre llenguatge C. Prèviament ha estat necessari automatitzar l'ajust del variograma que millor s'adapta a la distribució espacial de la variable d'estudi. Els resultats experimentals demostren la validesa de la solució implementada, en reduir de forma significativa els temps d'execució final de tot el procés.El principal objetivo de este trabajo es proporcionar una metodología para reducir el tiempo de cálculo del método de interpolación kriging sin pérdida de la calidad del modelo resultado. La solución adoptada ha sido la paralelización del algoritmo mediante MPI sobre lenguaje C. Previamente ha sido necesario automatizar el ajuste del variograma que mejor se adapta a la distribución espacial de la variable de estudio. Los resultados experimentales demuestran la validez de la solución implementada, al reducir de forma significativa los tiempos de ejecución finales del proceso completo.The main objective of this work is to provide a methodology to reduce the time needed to calculate the kriging interpolation method without losing any quality of the resulting model. The solution adopted has been the algorithm parallelization by MPI on C language. Previously, it has been necessary to automate the variogram fitting that best suits the spatial distribution of the variable at study. The experimental results demonstrate the validity of the implemented solution, to significantly reduce the execution times of the entire process