Jorge Delgado García

Unmanned Aerial Systems (UAS) for environmental applications special issue preface

Drones are indeed a key new technology for remote sensing, and one that has grown rapidly in recent years. According to the database, Web of Science (published by Clarivate Analytics), the first significant use in IJRS of any of the terms UAS, unmanned aerial vehicle (UAV) or drones, for example, in the title, abstract, or keyword of an article, was in 2009, in a paper by Dunford et al. (2009). It was not until 2012 that another paper used one of those terms. After that, the numbers increased very quickly, and by 2017, IJRS published 68 papers that referenced these terms. Most notably, 2017 also saw the first IJRS special issue on UAS, titled ‘Unmanned aerial vehicles for environmental applications’ (The Editors 2017). This current special issue is a direct follow-on from that major collection of papers, and the fact that we are able to have two major special issues on this topic in the space of just over one year, is further evidence of its importance

Extracción Automática de Edificios a partir de Modelos Digitales de Superficies : el sistema BUILDING

En este trabajo se plantea una aproximacion al complicado problema de la localizacion, extraccion y representacion vectorial de manera semiautomatica de edificaciones situadas en zonas urbanas o suburbanas, a partir del analisis de modelos de superficie, lo suficientemente densos como para representar la escena urbana, y de imagenes aereas orientadas de la zona de estudio. Elmetodo propuesto utiliza como informacion de partida losmodelos digitales de superficie generados de forma automaticamediante tecnicas fotogrametricas o de sistemas LIDAR con una densidad demalla elevada, asi como de un modelo previo de forma geometrica de los edificios existentes en la zona. Estos modelos de superficie, seran tratados mediante operaciones de morfologia matematica para la diferenciar los puntos que pertenecen al terreno propiamente dicho, de los pertenecientes a objetos situados sobre el, asi como por momentos geometricos invariantes para obtener el rectangulo representativo del objeto localizado. Una vez localizados los posibles edificios, asi como los rectangulos que representan a cada uno de ellos, se procedera a refinar estos resultados trabajando sobre los fotogramas aereos correspondientes. Mediante analisis digital de imagenes se realizara una extraccion de bordes y con la ayuda de la transformada de Hough se obtendra el rectangulo principal de la imagen. Este rectangulo junto con la altura delmismo extraida en la fase anterior, formara el prisma de base rectangular que representara al edificio. Todas estas operaciones han sido implementadas en un sistema de desarrollo propio, el sistema BUILDING, cuyos resultados iniciales son presentados en este trabajo para poner de manifiesto las posibilidades y problemas de la metodologia propuesta. In this work we present an approximation to the complicated problem of the semiautomatic location, extraction and vector representation of buildings. This approximation is based on surface obtained from the high-density model analysis and of the oriented aerial images of a determinate area. The proposed method uses as input information the digital surface models (obtained from photogrammetric process or LIDAR mapping data capture according to a very high density grid) and a previous geometric model of the form of the existent buildings in the zone. The surface models will be processed using mathematical morphology operators in order to classify ground points and non-ground points. Furthermore, the regions that have been classified as non-ground regions will be processed using invariant geometric moments in order to obtain the representative rectangle of localized object. Once the possible buildings have been detected, their representative rectangles are defined. The results will be refined using the complementary information provided by aerial photogrammetric imagery. Using digital image analysis procedures it is possible to extract the main borders presented in the images and applying the Hough’s transform the principal rectangle will be obtained. This rectangle combined with the heights obtained from the DSM in the same location, constitute the rectangular base prism that represent to the building. All these operations have been implemented in an own developed system,whose preliminary results are presented in this works in order to establish the capabilities and problems of the methodology.

Evaluacion de macroceldas de corrosion embebidos en vigas de concreto reforzado bajo ambiente salino

In this work, corrosion of reinforcing steel in concrete beams exposed to two environments was evaluated. The two environments used were: drinking water (white) and salt water (5% NaCl sol.) for 18-months. The concrete had a water/cement ratio of 0.40 and 0.60, respectively. Monitoring was carried out by measuring macrocell voltage and current, with open-circuit potentials and electrochemical noise. The results presented more probability of corrosion in beams immersed in salt water with higher water/cement ratios and reaching the system a state of passivation. The macrocells were very useful for analyzing the corrosion system and correlated electrochemical techniques.