Detección de errores temáticos en el CORINE Land Cover a través del estudio de cambios: Comunidad de Madrid (2000-2006)

Thematic cartography use to be the starting point in several works. It is necessary to be careful with the errors that data source may have to achieve a good outcome. Using a simple methodology we can identify thematic errors in the CORINE Land Cover cartography from the years 2000 and 2006 through the database intersection. That map intersection will give us a group of stable and changing polygons and a cross tabulation matrix with which the surface gain or loss can be interpreted. By means of studies through sampling stable and changing polygons and their verification with orthophotos we can find several thematic errors in the cartography used. Besides, the use of confusion matrices determines the level of global accuracy and categories most prone to error.La cartografía temática suele ser el punto de partida en muchos trabajos. Es necesario tener cuidado con los errores que pueda presentar la fuente de datos para conseguir un buen resultado. Utilizando una sencilla metodología se pueden determinar errores temáticos en las cartografías CORINE Land Cover de los años 2000 y 2006 a través de la intersección de ambas bases de datos. Dicha intersección de mapas nos dará una serie de polígonos estables y de cambio y una matriz de cruce con la que interpretar el balance de superficie ganada o perdida. Mediante el estudio a través de muestreos de los diferentes tipos de cambio y su verificación con ortofotos se puede llegar a encontrar diversos errores de asignación temática en las cartografías empleadas. Además, el uso de las matrices de confusión permite establecer el nivel de exactitud global y de las categorías más propensas a errores. [fr] La cartographie thématique est généralement le point de départ pour de nombreuses activités. Des précautions doivent être prises pour les erreurs qui peuvent survenir dans la source de données pour obtenir un bon résultat. En utilisant une méthode simple permet de déterminer les erreurs dans les cartes thématiques de la CORINE Land Cover 2000 et 2006 par l’intersection de deux bases de données. Cette intersection des cartes nous donnent un ensemble de polygones stables et de changement et une matrice du croisement avec laquelle interpréter le bilan de surface gagnée ou perdue. Au moyen de l’étude à travers des échantillonnages de différents taux de change et sa vérification avec ortofotos on peut arriver à trouver de diverses erreurs d’assignation thématique dans la cartographie employée. De plus, l’usage des matrices de confusion permet d’établir le niveau d’exactitude globale et des catégories les plus enclines aux erreurs

Sensitivity analysis for cellular-automata based models. A methodological approach on prospective scenario assessment

En el presente trabajo se desarrolla una propuesta que podría formar parte de un proceso de validación para modelos prospectivos (no necesariamente predictivos) de simulación del crecimiento urbano basado en autómatas celulares (AC). Concretamente, se plantea la aplicación de un análisis de sensibilidad que pretende explorar el grado de influencia de cada uno de los parámetros de los modelos tradicionalmente empleados en la simulación del crecimiento urbano, valorando si la ausencia de uno o varios de ellos supone una alteración significativa de los resultados. Para ello se ha empleado un modelo desarrollado para simular un crecimiento urbano futuro deseable en la Comunidad de Madrid y que, por tanto, no se limita a reproducir en el futuro lo acontecido en el pasado, aplicación que tradicionalmente se ha llevado a cabo con los modelos basados en AC. La propuesta se basa en la generación de diferentes versiones del modelo derivadas de la eliminación de diversos parámetros de los que conforman la versión original. Los resultados muestran la gran influencia de factores como la aptitud y la vecindad. La evaluación de los resultados del análisis de sensibilidad, por otro lado, nos ofrece información interesante sobre aquellas localizaciones que podríamos considerar soluciones robustas del modelo y que, por tanto, minimizarían el riesgo asumido al tomar la decisión de urbanizarlas.This paper presents a Sensitivity Analysis (SA) as part of a validation procedure to be applied to prospective models for urban simulation growth based on Cellular Automata (CA). This SA explores the influence of each factor integrating the CA model on the results to simulate the future urban growth in Madrid region. The proposal is based on the generation of different versions of the original model, erasing one factor at a time. The results show a relevant influence of the suitability and neighbourhood factors. The evaluation of the results of the SA also offers interesting information about those locations that could be considered robust solutions of the model (in order to be urbanized), minimizing the decision risk.Ministerio de Educación y Cienci

Análisis de Sensibilidad aplicado a modelos de crecimiento urbano basados en autómatas celulares de estructura irregular

This work presents a Sensitivity Analysis (SA), as part of a validation process that is applied on an urban growth Cellular Automata (CA) based-model with irregular structure (MUGICA, Model for Urban Growth simulation using an Irregular Cellular Automata). This model has been developed to simulate urban growth of three municipalities located in an important industrial corridor (Corredor del Henares) in the central area of Spain. Although the methodology employed in this work has already been applied in models based on a raster structure, it is intended to verify its viability in the previous simulation phase, that is, in the calibration period (2000-2010) in a model of irregular structure such as MUGICA, which uses the cadastral plot as reference unit. This procedure aims to explore the degree of influence of each of the parameters on the results of the model, individually and as a whole. For this purpose, a successive elimination of the parameters is performed to evaluate if the absence of one or several of them implies a significant alteration of the results. The results show, firstly, the viability to apply this methodology in a vector environment. On the other hand, it has been possible to verify the significative influence of the suitability and accessibility factors in the development of urban land, as would be expected in a model of these characteristics.En el presente trabajo se aplica un Análisis de Sensibilidad (AS), como parte de un proceso de validación, sobre un modelo de simulación del crecimiento urbano basado en Autómatas Celulares (AC) de estructura irregular (MUGICA, Model for Urban Growth simulation using an Irregular Celular Automata). Este modelo ha sido desarrollado para simular el crecimiento urbano de tres municipios pertenecientes a un importante corredor urbano-industrial (Corredor del Henares) localizado en la zona central peninsular de España. Si bien la metodología utilizada en este trabajo ya ha sido aplicada en modelos basados en una estructura raster, se pretende comprobar su viabilidad en un modelo de estructura irregular como MUGICA, el cual emplea la parcela catastral como unidad de referencia. El objetivo es explorar el grado de influencia de cada uno de los factores en los resultados del modelo, de manera individual y en sus diferentes combinaciones. Para ello se realiza una eliminación sucesiva de los factores con el fin de evaluar si la ausencia de uno o varios de ellos supone una alteración significativa de los resultados. Los resultados muestran, en primer lugar, la viabilidad de la aplicación de esta metodología en este tipo de entorno irregular. Por otro lado, se ha podido constatar la gran influencia de los factores accesibilidad y aptitud en el desarrollo de suelo urbano, como sería de esperar en un modelo de estas características

Simulación prospectiva del crecimiento urbano en la Comunidad Autónoma de Madrid a partir de modelos basados en autómatas celulares y modelos basados en EMC

En el presente trabajo se analizan los resultados de varias simulaciones prospectivas de crecimiento urbano, entre los años 2000 y 2020, realizadas en la Comunidad de Madrid, aplicando dos modelos diferentes: uno basado en Autómatas Celulares (AC) y otro en técnicas de Evaluación MultiCriterio (EMC). El objetivo es comparar los resultados de las simulaciones de ambos modelos para detectar si se aproximan o están fuertemente influidos por la técnica empleada. Esto también permitiría, en cierta forma, evaluar los modelos desarrollados y su utilidad, pudiendo generar una cartografía de los resultados más robustos, es decir, de localizaciones que reiteradamente aparecen en las distintas simulaciones como las más apropiadas para desarrollar una futura ocupación urbana. En este caso concreto, se ha podido comprobar la escasa coincidencia entre resultados, evidenciando la necesidad, por un lado, de utilizar metodologías de comparación de mapas más flexibles, que permitan valorar mejor las semejanzas/diferencias encontradas, y, por otro, de detectar particularidades de los modelos que estén condicionando los resultados e, inclusive, deficiencias en su desarrollo.Proyecto SIMURBAN2: Instrumentos de Geosimulación y planificación ambiental en la ordenación territorial de ámbitos metropolitanos. Aplicación a escalas intermedias (Ref.: CSO2012-38158-C02-01)

Configuring the neighbourhood effect in irregular cellular automata based models

Cellular automata (CA) models have been widely employed to simulate urban growth and land use change. In order to represent urban space more realistically, new approaches to CA models have explored the use of vector data instead of traditional regular grids. However, the use of irregular CA-based models brings new challenges as well as opportunities. The most strongly affected factor when using an irregular space is neighbourhood. Although neighbourhood definition in an irregular environment has been reported in the literature, the question of how to model the neighbourhood effect remains largely unexplored. In order to shed light on this question, this paper proposed the use of spatial metrics to characterise and measure the neighbourhood effect in irregular CA-based models. These metrics, originally developed for raster environments, namely the enrichment factor and the neighbourhood index, were adapted and applied in the irregular space employed by the model. Using the results of these metrics, distance-decay functions were calculated to reproduce the push-and-pull effect between the simulated land uses. The outcomes of a total of 55 simulations (five sets of different distance functions and eleven different neighbourhood definition distances) were compared with observed changes in the study area during the calibration period. Our results demonstrate that the proposed methodology improves the outcomes of the urban growth simulation model tested and could be applied to other irregular CA-based models

A search for ultra-high-energy photons at the Pierre Auger Observatory exploiting air-shower universality

The Pierre Auger Observatory is the most sensitive detector to primary photons with energies above ∼0.2 EeV. It measures extensive air showers using a hybrid technique that combines a fluorescence detector (FD) with a ground array of particle detectors (SD). The signatures of a photon-induced air shower are a larger atmospheric depth at the shower maximum (X$_{max}$) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced background. Using observables measured by the FD and SD, three photon searches in different energy bands are performed. In particular, between threshold energies of 1-10 EeV, a new analysis technique has been developed by combining the FD-based measurement of X$_{max}$ with the SD signal through a parameter related to its muon content, derived from the universality of the air showers. This technique has led to a better photon/hadron separation and, consequently, to a higher search sensitivity, resulting in a tighter upper limit than before. The outcome of this new analysis is presented here, along with previous results in the energy ranges below 1 EeV and above 10 EeV. From the data collected by the Pierre Auger Observatory in about 15 years of operation, the most stringent constraints on the fraction of photons in the cosmic flux are set over almost three decades in energy

Study on multi-ELVES in the Pierre Auger Observatory

Since 2013, the four sites of the Fluorescence Detector (FD) of the Pierre Auger Observatory record ELVES with a dedicated trigger. These UV light emissions are correlated to distant lightning strikes. The length of recorded traces has been increased from 100 μs (2013), to 300 μs (2014-16), to 900 μs (2017-present), to progressively extend the observation of the light emission towards the vertical of the causative lightning and beyond. A large fraction of the observed events shows double ELVES within the time window, and, in some cases, even more complex structures are observed. The nature of the multi-ELVES is not completely understood but may be related to the different types of lightning in which they are originated. For example, it is known that Narrow Bipolar Events can produce double ELVES, and Energetic In-cloud Pulses, occurring between the main negative and upper positive charge layer of clouds, can induce double and even quadruple ELVES in the ionosphere. This report shows the seasonal and daily dependence of the time gap, amplitude ratio, and correlation between the pulse widths of the peaks in a sample of 1000+ multi-ELVES events recorded during the period 2014-20. The events have been compared with data from other satellite and ground-based sensing devices to study the correlation of their properties with lightning observables such as altitude and polarity

Extraction of the Muon Signals Recorded with the Surface Detector of the Pierre Auger Observatory Using Recurrent Neural Networks

We present a method based on the use of Recurrent Neural Networks to extract the muon component from the time traces registered with water-Cherenkov detector (WCD) stations of the Surface Detector of the Pierre Auger Observatory. The design of the WCDs does not allow to separate the contribution of muons to the time traces obtained from the WCDs from those of photons, electrons and positrons for all events. Separating the muon and electromagnetic components is crucial for the determination of the nature of the primary cosmic rays and properties of the hadronic interactions at ultra-high energies. We trained a neural network to extract the muon and the electromagnetic components from the WCD traces using a large set of simulated air showers, with around 450 000 simulated events. For training and evaluating the performance of the neural network, simulated events with energies between 1018.5, eV and 1020 eV and zenith angles below 60 degrees were used. We also study the performance of this method on experimental data of the Pierre Auger Observatory and show that our predicted muon lateral distributions agree with the parameterizations obtained by the AGASA collaboration