Xavier Pons
Universitat Autònoma de Barcelona, Departament de Geografia, Faculty Member
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sensing as a tool to map forest fires, to study the fire regime and their effects on plant communities and
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Se presenta la metodologia utilizada en la obtencion de la cartografia de usos y cubiertas del suelo para la zona oriental de Andalucia (ambito de 29.259 km²) en el quinquenio 2000-2004, empleando el clasificador hibrido y utilizando... more
Se presenta la metodologia utilizada en la obtencion de la cartografia de usos y cubiertas del suelo para la zona oriental de Andalucia (ambito de 29.259 km²) en el quinquenio 2000-2004, empleando el clasificador hibrido y utilizando imagenes Landsat junto con las variables auxiliares. Las areas de entrenamiento se han obtenido de manera semiautomatica a partir del SIOSE y depuradas con umbrales de NDVI. Se han ejecutado bancos de pruebas en funcion de las variables incluidas en el clasificador. Los mejores resultados, en cuanto a porcentaje de acierto y area clasificada,se han obtenido excluyendo la radiacion solar de invierno y la banda 1. El proceso se ha realizado por separado para cubiertas naturales y urbanas, con un grado de acierto global superior al 88%, y para cultivos, con un acierto superior al 86%.
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La reflectividad derivada de imagenes satelitales sigue generalmente el ciclo fenologico de las cubiertas presentes en el territorio. A pesar de ello, es posible encontrar zonas donde la reflectividad es practicamente invariante. Estas... more
La reflectividad derivada de imagenes satelitales sigue generalmente el ciclo fenologico de las cubiertas presentes en el territorio. A pesar de ello, es posible encontrar zonas donde la reflectividad es practicamente invariante. Estas areas definidas como pseudoinvariantes (API) permiten comparar y calibrar imagenes provenientes de distintos sensores y procesar series temporales con una elevada coherencia. Se presenta un nuevo metodo automatico (especialmente util en entornos Big Data) para seleccionar API a partir del producto diario MOD09GA derivado de imagenes Terra-MODIS, utilizando una serie temporal de 14 anos y las bandas del espectro solar (visible, infrarrojo cercano y de onda corta) con una resolucion espacial de 500 m. Dicha metodologia consta de dos etapas de filtrado, una primera que evalua la calidad de las imagenes de la serie mediante tecnicas geoestadisticas, seleccionando las mejores, y una segunda que define umbrales especificos para cada banda espectral, en func...
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Field spectroradiometers are key instruments for the synergetic work with airborne and satellite imagery. However, there is limited information about the technical details of their performance. The objective of this study is to set and... more
Field spectroradiometers are key instruments for the synergetic work with airborne and satellite imagery. However, there is limited information about the technical details of their performance. The objective of this study is to set and validate the optimum measurement protocol for a spectroradiometer operating in the visible and near infrared wavelengths. We assessed the protocol followed to measure field reflectances of natural and artificial objects. We then validated the data with hyperspectral measurements simultaneously acquired by airborne and satellite sensors. The spectroradiometer studied is the Ocean Optics USB2000+ (200-1100 nm) and the airborne sensors are CASI-550 (410- 962 nm) and AISA Eagle II (406-994 nm).
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Accurate mapping of open-pit mine areas is a prerequisite for the efficient resource management of extractive companies, but also detailed mapping is a requirement for public administrations, especially regarding the monitoring of... more
Accurate mapping of open-pit mine areas is a prerequisite for the efficient resource management of extractive companies, but also detailed mapping is a requirement for public administrations, especially regarding the monitoring of restored areas. In previous works, our team has contributed to a better knowledge of the use of Unmanned Aerial Systems (UAS) technologies for soil/vegetation restoration monitoring purposes, and in this work, we present a novel protocol to support combined interests of both private companies and governmental agencies. We introduce a case study in which we show the capability of multispectral sensors onboard of a low-weight multicopter to describe land cover typologies in restored areas (such as grass, scrubs, trees, topsoil and mine spoils) by applying remote sensing and GIS techniques. Moreover, we assess the capability of digital terrain models (Digital Elevation Model, Digital Surface Model, Digital Slope Model) derived from photogrammetric techniques,...
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Los cambios en los usos del suelo afectan a la biodiversidad y son uno de los principales componentes del cambio global. Durante las últimas décadas las áreas montañosas del noroeste peninsular han estado sometidas a un abandono del medio... more
Los cambios en los usos del suelo afectan a la biodiversidad y son uno de los principales componentes del cambio global. Durante las últimas décadas las áreas montañosas del noroeste peninsular han estado sometidas a un abandono del medio rural que ha provocado una intensa dinámica de cambios en las cubiertas del suelo. En los últimos años los datos procedentes de Landsat han sido ampliamente utilizados en el cartografiado de las cubiertas del suelo a través de clasificación multiespectral, siendo particularmente útiles en áreas montañosas donde la accesibilidad es limitada. En este trabajo evaluamos las dinámicas temporales de las cubiertas y usos del suelo ocurridos en una zona montañosa del NW de la Península Ibérica durante el período 2000-2010, mediante una comparación post-clasificación y tres índices de área relativa. Dicha evaluación incluye: 1) la corrección radiométrica de las imágenes Landsat, 2) la definición precisa de las áreas de entrenamiento y 3) la incorporación de...
The work that we present is a part of a general study aimed to characterize the fire regimes in Catalonia (NorthEast of Spain) and the effects of wildfires on regeneration dynamics of plant communities. For that purpose, a semi-automatic... more
The work that we present is a part of a general study aimed to characterize the fire regimes in Catalonia (NorthEast of Spain) and the effects of wildfires on regeneration dynamics of plant communities. For that purpose, a semi-automatic method was applied to de- tect burned forest areas in the 3 million ha region of Catalonia. The methodology employed more than a hundred of MSS images from Landsat satellites com- prising a period of time of 19 years. (1975-1993). They were geometrical and radiometrically corrected and the time series was registered. NDVI images were com- posed. Some masks were applied in order to avoid changes on plant cover dues to different causes. Sub- traction of consecutive NDVI images was employed to locate the forest areas affected by fire. This approach is based on the sudden decline that the plant commu- nities undergone when they burn. Linear regression models were used to fit the empirical changes observed for several test fires with NDVI differences bet...
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Geospatial data is used not only to contemplate reality but also, in combination with analytical tools, to generate new information that requires interpretation. In this process data users gain knowledge about the data and its limitations... more
Geospatial data is used not only to contemplate reality but also, in combination with analytical tools, to generate new information that requires interpretation. In this process data users gain knowledge about the data and its limitations (the user side of data quality) as well as knowledge on the status and evolutions of the studied phenomena. Knowledge can be annotations on top of the data, responses to questions, a careful description of the processes applied, a piece of software code or scripts applied to the data, usage reports or a complete scientific paper. This paper proposes an extension of the current Open Geospatial Consortium standard for Geospatial User Feedback to include the required knowledge elements, and a practical implementation. The system can incrementally collect, store, and communicate knowledge elements created by users of the data and keep them linked to the original data by means of permanent data identifiers. The system implements a Web API to manage feed...
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Resum En aquest article es descriu l'evolució històrica de les tres principals fonts per localitzar les cobertes i usos del sòl (CUS): el treball de camp, la fotografia aèria i la teledetecció amb imatges de satèl·lit. A continuació,... more
Resum En aquest article es descriu l'evolució històrica de les tres principals fonts per localitzar les cobertes i usos del sòl (CUS): el treball de camp, la fotografia aèria i la teledetecció amb imatges de satèl·lit. A continuació, s'analitza el mètode més emprat a l'hora de quantificar els canvis de les CUS, la comparació postclassificació o superposició de ma-pes, per tal d'indicar-ne les principals problemàti-ques que pot comportar. Finalment, es presenta un exemple d'anàlisi de canvis de CUS (de 1977 a 1997) de vint-i-un municipis de l'Alt Empordà a partir d'imatges de satèl·lit. MOTS CLAU: cobertes i usos del sòl, treball de camp, fotografia aèria, teledetecció amb imatges de satèl·lit, comparació postclassificació. Abstract The evolution of methods and instruments for the detection of land cover and land use and for the analysis of changes in them This paper describes the historical evolution of the three main sources for the study of land cover a...
Remote Sensing (RS) digital classification techniques require sufficient, accurate and ubiquitously distributed ground truth (GT) samples. GT is usually considered “true” per se; however, human errors, or differences in criteria when... more
Remote Sensing (RS) digital classification techniques require sufficient, accurate and ubiquitously distributed ground truth (GT) samples. GT is usually considered “true” per se; however, human errors, or differences in criteria when defining classes, among other reasons, often undermine this veracity. Trusting the GT is so crucial that protocols should be defined for making additional quality checks before passing to the classification stage. Fortunately, the nature of RS imagery allows setting a framework of quality controls to improve the confidence in the GT areas by proposing a set of filtering rules based on data from the images themselves. In our experiment, two pre-existing reference datasets (rDS) were used to obtain GT candidate pixels, over which inconsistencies were identified. This served as a basis for inferring five key filtering rules based on NDVI data, a product available from almost all RS instruments. We evaluated the performance of the rules in four temporal stu...
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Research Interests: Landscape Ecology, Geography, Earth Sciences, Environmental Science, Remote Sensing, and 11 moreConservation planning, Biological Sciences, Environmental Sciences, Land Cover, Forest Management, Solar radiation, Spatial Pattern, Size Distribution, Fractal Dimension, Environmental Parameter, and Lorenz Curve
Lineage information is the part of the metadata that describes “what”, “when”, “who”, “how”, and “where” geospatial data were generated. If it is well-presented and queryable, lineage becomes very useful information for inferring data... more
Lineage information is the part of the metadata that describes “what”, “when”, “who”, “how”, and “where” geospatial data were generated. If it is well-presented and queryable, lineage becomes very useful information for inferring data quality, tracing error sources and increasing trust in geospatial information. In addition, if the lineage of a collection of datasets can be related and presented together, datasets, process chains, and methodologies can be compared. This paper proposes extending process step lineage descriptions into four explicit levels of abstraction (process run, tool, algorithm and functionality). Including functionalities and algorithm descriptions as a part of lineage provides high-level information that is independent from the details of the software used. Therefore, it is possible to transform lineage metadata that is initially documenting specific processing steps into a reusable workflow that describes a set of operations as a processing chain. This paper p...
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This study analyzes the spatio-temporal dynamics of the drivers of forest expansion in the Iberian Peninsula for the periods 1987–2002–2017 through a 185 km-wide north–south Landsat scene transect. The analysis has considered a variety of... more
This study analyzes the spatio-temporal dynamics of the drivers of forest expansion in the Iberian Peninsula for the periods 1987–2002–2017 through a 185 km-wide north–south Landsat scene transect. The analysis has considered a variety of biogeographical regions [0–3500 m.a.s.l, annual rainfalls 150–2200 mm] and 30 explanatory variables. A rigorous map production at 30 m resolution, including detailed filtering methods and uncertainty management at pixel scale, provided high-quality land cover maps. The main forest expansion trajectories were related to explanatory variables using boosted regression trees. Proximity to previous forests was a key common factor for forest encroachment in all forest types, with other factors being distance to the hydrographic network, temperature and precipitation for broadleaf deciduous forests (BDF), precipitation, temperature and solar radiation for broadleaf evergreen forests (BEF) and precipitation, distance to province capitals, and solar radiati...
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In emergency situations, it is of paramount importance that accurate assessments showing what is happening in the field, and when and where it is happening, are distributed quickly. This increases the aid workers' awareness of the... more
In emergency situations, it is of paramount importance that accurate assessments showing what is happening in the field, and when and where it is happening, are distributed quickly. This increases the aid workers' awareness of the situation and can be used to organize the workers more efficiently. The increasing number of satellite images available means that new data can be obtained rapidly and the information can be kept constantly up to date. These data can be distributed easily using open standards over the Internet. In a large post-disaster event, the demand for information increases dramatically, which can negatively impact the performance of the services provided. Here, we assess seven of the most popular server solutions (GeoServer, MapServer, MiraMon Map Server, Express Server, ArcGIS Server, TileCache and GeoWebCache) for map service standards (WMS, WMTS, WMTS-C, TMS), and compare their response times, user functionalities and usability.
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This is a document issuing from the project: Linking Pan-European Landcover Change to Pressures on Biodiversity (BIOPRESS); a project funded by the European Commission DG Research under the specific research and technological development... more
This is a document issuing from the project: Linking Pan-European Landcover Change to Pressures on Biodiversity (BIOPRESS); a project funded by the European Commission DG Research under the specific research and technological development programme “Energy, Environment and Sustainable Development” and the “Global Monitoring for the Environment and Security” initiative of the Fifth Framework Programme (GMES: http://www.gmes.info/). The main objective of the BIOPRESS project was to determine historical changes (1950 – 1990 – 2000) in land cover across Europe for the purpose of measuring changes in habitats and their biodiversity. The BIOPRESS project is strongly linked to CORINE Land Cover project, as it uses the same 44 class nomenclature (CORINE Land Cover nomenclature: http://reports.eea.eu.int/COR0-landcover/en). The adopted approach was to sample Europe using 2 x 15 km transects and 30 x 30 km windows, containing one or more Natura-2000 sites, and establish changes by finding and ...
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Research Interests: Landscape Ecology, Earth Sciences, Landscape, Biological Sciences, Environmental Sciences, and 15 moreLand Cover, Fragmentation, Patch Size, Iberian Peninsula, Land cover change, Agricultural land use change, Landscape Pattern, Human Activity, Nearest Neighbour, Land Cover Mapping, Diversity index, Landscape Heterogeneity, Fire regime, Normalized Difference Vegetation Index, and agricultural land
Research Interests: Botany, Geography, Forestry, Climate Change, Conservation Biology, and 15 moreDisaster risk management, Fire Ecology, Forest Ecology And Management, Biology, Ecology, Forest Ecology, Indigenous Peoples, Global Warming, Global change, Biodiversity Research, global Climate change, Forest Management, Forest succession, Ecological Applications, and Alpine and Arctic Research
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En el presente número 18 de GeoFocus, el segundo de 2016, se nos presentan 10 trabajos en que la Ciencia y la Tecnología de la Información Geográfica hace aportaciones en áreas tan diversas como la evaluación multicriterio (Belenguer;... more
En el presente número 18 de GeoFocus, el segundo de 2016, se nos presentan 10 trabajos en que la Ciencia y la Tecnología de la Información Geográfica hace aportaciones en áreas tan diversas como la evaluación multicriterio (Belenguer; Domínguez-Walle, Vargas-Tristán, Pérez, Niño-Maldonado, Treviño-Carreón, Herrera), toponimia [gracias a una de las muchísimas aplicaciones que tiene esta relativamente reciente -al menos en su uso generalizadoforma de teledetección que es el lidar] (Membrado), gestión territorial (Lanceta, Entraigas, de Dominicis, Vercelli), fusión de imágenes de teledetección (Borini, Montorio, Pérez-Cabello, Vlassova), prospectiva (Naranjo, Gutiérrez, Ruíz, Cuadrado), riesgos biológicos (Manzano, Folgueiras, Germinal, Prieto), gestión de recursos públicos (Nieto, Cárdenas), recursos renovables (Martín, Domínguez, Amador) o accesibilidad viaria (López-Escolano, Pueyo, Postigo, Alonso).
can save the status of the application and share this status with other users that need to deal with the same information and use different client vendor products in an interoperable way. The extensibility of the Atom format was essential... more
can save the status of the application and share this status with other users that need to deal with the same information and use different client vendor products in an interoperable way. The extensibility of the Atom format was essential to define a format that could be used in RSS enabled web browser, Mass Market map viewers and emerging geospatial enable integrated clients that support Open Geospatial Consortium (OGC) services. The status exchange between a web client application and Geographic Information System desktop solution is demonstrated.
Following the previous works of the atlas of Catalonia and the atlas of the peninsular Spain, we have obtained a digital cartography for the Balearic Islands. This methodology of climatic interpolation uses GIS tools, statistical analysis... more
Following the previous works of the atlas of Catalonia and the atlas of the peninsular Spain, we have obtained a digital cartography for the Balearic Islands. This methodology of climatic interpolation uses GIS tools, statistical analysis (multiple regression) and exclusively mathematical interpolation methods. The data of the meteorological stations (mean air temperature –minimum, mean and maximum– and precipitation) are used as dependent variables and different geographical factors (altitude, latitude, continentality, solar radiation and terrain curvature) are used as independent variables to compute the interpolation. Also we have developed a comparison of the behavior of the geoclimatic variables in function of whether the studied area is a peninsula or an island.
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Many spatial applications require the use of Digital Terrain Models (DTM) of variables such as elevation, climate, etc. Although there often exists such models in the form of a raster DTM, in some cases the only terrain model that is... more
Many spatial applications require the use of Digital Terrain Models (DTM) of variables such as elevation, climate, etc. Although there often exists such models in the form of a raster DTM, in some cases the only terrain model that is available is in the form of less adequate models such as isolines (contour lines, isotherms, etc.). When such is the case it is not a trivial process to obtain a MDT since isolines present some special geostatistical properties. Additionally, other complementary data sources of height and morphology information should not be discarded in the process of DTM generation, despite the fact that their data size makes them seem of less importance. This work presents a methodology for obtaining raster DTMs which makes use of the different datasets available: isolines, 2D and 3D breaklines, polygonal zones with constant value (e.g. lakes), point data, nodata zones, 3D objects (e.g., roads), etc. The implemented methodology is not a single algorithm but a set of ...
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La obtención de datos de fenología de la vegetación natural y los cultivos resulta imprescindible para obtener mapas detallados (más de 20 categorías de esta temática) a partir de clasificación de imágenes. Para dicho fin se requiere del... more
La obtención de datos de fenología de la vegetación natural y los cultivos resulta imprescindible para obtener mapas detallados (más de 20 categorías de esta temática) a partir de clasificación de imágenes. Para dicho fin se requiere del uso de múltiples fechas de adquisición. Sin embargo, esta variedad de fechas suele conllevar la presencia de sombras, nubes, nieves, etc, que acarrean la pérdida de una importante superficie clasificable. En esta comunicación se presenta un clasificador no supervisado (IsoMM) que permite un mejor aprovechamiento de las imágenes de una serie temporal gracias a un particular tratamiento de los valores NoData. El nuevo algoritmo ha sido aplicado a la obtención de mapas de zonas forestales y agrícolas de varios miles de ha, con una leyenda de más de 25 categorías en dichas zonas usando imágenes Landsat. En este escenario IsoMM permite clasificar hasta un 40% más de superficie respecto al tratamiento habitual, manteniendo un acierto global del 90%.
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Georeferencing satellite images is an essential pro cedure to carry out most remote sensing applications. The quality of this process w ill affect all the ulterior procedures and products. Independent test ground co ntrol points (GCPs)... more
Georeferencing satellite images is an essential pro cedure to carry out most remote sensing applications. The quality of this process w ill affect all the ulterior procedures and products. Independent test ground co ntrol points (GCPs) are required to assess the quality of the correction. H owever, a representative number is hardly obtained when they are manually located. This work studies the effect of the number of GCPs in the geometric correction qual ity when they are manually located. The methodology has been applied to Landsa t TM images in a region with complex relief (heights ranging from 0 to 3000+ m). The work presents a spatial representation of the error and discusses its role in the visualisation of the quality. Moreover, we critically discuss the usage of indica tors as the RMS error without considering the number of GCPs or the method used i n their placement in the realistic assessment of the geometric quality of th e imagery. Indeed, it is shown that, for the studie...
This paperpresents a semiautomatic methoaotogy forfira scars mapping from a time series of Landsat MSS images over the forest surface of Catalonia (1975- 1993). This series has deen enlarged from two years of TM images (1994-1995).... more
This paperpresents a semiautomatic methoaotogy forfira scars mapping from a time series of Landsat MSS images over the forest surface of Catalonia (1975- 1993). This series has deen enlarged from two years of TM images (1994-1995). Results are a map series offire history during 21 years as well as fire recurrence level. Omission errors are 23 % for bumed areas greater than 200 ha while commissior) errors are 8% for areas greater than 50 ha. Detected fire scars were incorporated into a geographic information system in order to characterise the fira regime ofthe study area. Fire size distribution and the numtjer ofspot fires originated from each fire as well as the maximum distance reached from the main fire are analysed. Sonw aspects aljoutpost-fire regeneraron monitoring through normalised difference vegetation index (NDVI) are also shown.
El trabajo comprueba el efecto de la compresion degradativa de imagenes sobre la clasificacion digital de zonas forestales. El metodo de clasificacion utilizado es una clasificacion mixta de imagenes de satelite y variables... more
El trabajo comprueba el efecto de la compresion degradativa de imagenes sobre la clasificacion digital de zonas forestales. El metodo de clasificacion utilizado es una clasificacion mixta de imagenes de satelite y variables topo-climaticas para la cartografia de cubiertas vegetales. Los resultados aportan interesantes novedades respecto a la influencia de la compresion en la calidad de la cartografia obtenida, tanto desde un punto de vista ‘por pixel’ como a nivel de homogeneidad de los poligonos obtenidos. La superficie clasificada en clasificaciones realizadas solo con variables radiometricas aumenta al aumentar la compresion de las imagenes, aunque el aumento es menor para formatos JPEG2000, especialmente en zonas fragmentadas. Por el contrario la superficie clasificada se reduce en las clasificaciones que ademas consideran variables topo-climaticas. El acierto global de las imagenes se reduce a elevadas compresiones, aunque el punto de inflexion se situa en diferentes lugares se...
A semiautomatic method to map forest fires during large periods by means of remote sensing imagery has been developed. This methodology has been applied to the period 1975-1993 and results have been given as a forest fire map series and a... more
A semiautomatic method to map forest fires during large periods by means of remote sensing imagery has been developed. This methodology has been applied to the period 1975-1993 and results have been given as a forest fire map series and a fire history map of Catalonia (Northeast of Spain). These maps have been lately converted to vector layers and all results have been integrated into a GIS. The results have been contrasted to independent administration data and commission and omission errors have been evaluated. Fire frequencies and NDVI post-fire values have been used to retrieve valuable information on the fire regime and to evaluate plant regeneration rates in Mediterranean plant communities. GIS tools are being used for further landscape analysis.
This paper shows the main aspects of technology in which the MiraMon Map Reader, a program of free diffusion for the distribution and exploration of geographical information through Internet or on CD, is based. The information can be... more
This paper shows the main aspects of technology in which the MiraMon Map Reader, a program of free diffusion for the distribution and exploration of geographical information through Internet or on CD, is based. The information can be raster (1 to 32 bits per pixel) or vector with topology, and is distributed using the most advanced algorithms of data compression. The information provided by the MiraMon Map Reader neither is a small part of the initial data nor a screen dump, but it supplies all the graphic, alphanumerical and documentary information of any type related to each map to be distributed. Data are certified to guarantee its integrity and the authorship of the distributor. The technology of the Reader is already working in two web servers and an important amount of geomatic data is distributed from them.
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Dep. Geografia. Universitat Autonoma de Barcelona. Cerdanyola del Valles, 08193. Jordi.Cristobal@uab.es. Dep. Biologia Animal, Vegetal y Ecologia. Unidad de Botanica. Universitat Autonoma de Barcelona. Cerdanyola del Valles, 08193.... more
Dep. Geografia. Universitat Autonoma de Barcelona. Cerdanyola del Valles, 08193. Jordi.Cristobal@uab.es. Dep. Biologia Animal, Vegetal y Ecologia. Unidad de Botanica. Universitat Autonoma de Barcelona. Cerdanyola del Valles, 08193. Miquel.Ninyerola@uab.es. Centro de Investigacion Ecologica y Aplicaciones Forestales (CREAF). Universitat Autonoma de Barcelona. Cerdanyola del Valles, 08193. Xavier.Pons@uab.es.
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This study focuses on the recovery of information from shadowed pixels in RGB or multispectral imagery sensed from unmanned aerial vehicles (UAVs). The proposed technique is based on the concept that a property characterizing a given... more
This study focuses on the recovery of information from shadowed pixels in RGB or multispectral imagery sensed from unmanned aerial vehicles (UAVs). The proposed technique is based on the concept that a property characterizing a given surface is its spectral reflectance, i.e., the ratio between the flux reflected by the surface and the radiant flux received by the surface, and this ratio is usually similar under direct-plus-diffuse irradiance and under diffuse irradiance when a Lambertian behavior can be assumed. Scene-dependent elements, such as trees, shrubs, man-made constructions, or terrain relief, can block part of the direct irradiance (usually sunbeams), in which part of the surface only receives diffuse irradiance. As a consequence, shadowed surfaces comprising pixels of the image created by the UAV remote sensor appear. Regardless of whether the imagery is analyzed by means of photointerpretation or digital classification methods, when the objective is to create land cover ...
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The main objective of this research is to apply unmanned aerial system (UAS) data in synergy with field spectroradiometry for the accurate radiometric correction of Landsat-8 (L8) and Sentinel-2 (S2) imagery. The central hypothesis is... more
The main objective of this research is to apply unmanned aerial system (UAS) data in synergy with field spectroradiometry for the accurate radiometric correction of Landsat-8 (L8) and Sentinel-2 (S2) imagery. The central hypothesis is that imagery acquired with multispectral UAS sensors that are well calibrated with highly accurate field measurements can fill in the scale gap between satellite imagery and conventional in situ measurements; this can be possible by sampling a larger area, including difficult-to-access land covers, in less time while simultaneously providing good radiometric quality. With this aim and by using near-coincident L8 and S2 imagery, we applied an upscaling workflow, whereby: (a) UAS-acquired multispectral data was empirically fitted to the reflectance of field measurements, with an extensive set of radiometric references distributed across the spectral domain; (b) drone data was resampled to satellite grids for comparison with the radiometrically corrected ...
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The present study illustrates an original methodology for estimating irrigation requirements and quantifying real water consumption in a long-established Mediterranean rural community (Delta Llobregat, Barcelona, Spain), combining data... more
The present study illustrates an original methodology for estimating irrigation requirements and quantifying real water consumption in a long-established Mediterranean rural community (Delta Llobregat, Barcelona, Spain), combining data from remote sensing, field mapping and in situ measurements. Because of land fragmentation and crop diversification, SPOT-5 imagery was used, given its spatial and temporal resolution and spectral attributes. Simultaneously, four flow meters were installed in two representative locations to measure water inputs and outputs every 5 min. Conveyance and irrigation efficiency were estimated for the entire irrigation community. The average conveyance efficiency was 46.8% and the classical and net irrigation efficiency reached 26.4 and 59.8%, respectively, with half of the water volume (55% or 3.2 hm3) returned to the river or diverted to wetlands, the maximum percentage of estimated error being about 3.4%. These results indicate an exceptionally high water loss rate due to the irrigation system (flooding), the ageing conveyance network and urban infrastructure breakdown. The applied protocol proved useful for monitoring low-efficiency irrigation systems in small communities experiencing intense urban and industrial pressures. Copyright © 2016 John Wiley & Sons, Ltd.