sensing as a tool to map forest fires, to study the fire regime and their effects on plant commun... more sensing as a tool to map forest fires, to study the fire regime and their effects on plant communities and
Se presenta la metodologia utilizada en la obtencion de la cartografia de usos y cubiertas del su... 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%.
La reflectividad derivada de imagenes satelitales sigue generalmente el ciclo fenologico de las c... 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...
Field spectroradiometers are key instruments for the synergetic work with airborne and satellite ... 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).
Accurate mapping of open-pit mine areas is a prerequisite for the efficient resource management o... 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,...
Los cambios en los usos del suelo afectan a la biodiversidad y son uno de los principales compone... 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 C... 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...
Geospatial data is used not only to contemplate reality but also, in combination with analytical ... 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...
Resum En aquest article es descriu l'evolució històrica de les tres principals fonts per loca... 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 ubiquitous... 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...
ISPRS International Journal of Geo-Information, 2021
Lineage information is the part of the metadata that describes “what”, “when”, “who”, “how”, and ... 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...
This study analyzes the spatio-temporal dynamics of the drivers of forest expansion in the Iberia... 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...
sensing as a tool to map forest fires, to study the fire regime and their effects on plant commun... more sensing as a tool to map forest fires, to study the fire regime and their effects on plant communities and
Se presenta la metodologia utilizada en la obtencion de la cartografia de usos y cubiertas del su... 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%.
La reflectividad derivada de imagenes satelitales sigue generalmente el ciclo fenologico de las c... 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...
Field spectroradiometers are key instruments for the synergetic work with airborne and satellite ... 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).
Accurate mapping of open-pit mine areas is a prerequisite for the efficient resource management o... 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,...
Los cambios en los usos del suelo afectan a la biodiversidad y son uno de los principales compone... 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 C... 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...
Geospatial data is used not only to contemplate reality but also, in combination with analytical ... 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...
Resum En aquest article es descriu l'evolució històrica de les tres principals fonts per loca... 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 ubiquitous... 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...
ISPRS International Journal of Geo-Information, 2021
Lineage information is the part of the metadata that describes “what”, “when”, “who”, “how”, and ... 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...
This study analyzes the spatio-temporal dynamics of the drivers of forest expansion in the Iberia... 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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