La compressió amb pèrdua en imatges destinades a la generació de cartografia temàtica : nous resultats

La compressió d'imatge amb pèrdua (e.g., JPEG i JPEG2000) permet elevades compressions (fins i tot reduint la imatge a menys d'un 10% de la seva grandària original) tot mantenint una qualitat notable. Tanmateix, hi ha hagut poques anàlisis quantitatives de les implicacions d'aquestes compressions quan s'utilitza classificació digital d'imatges per a generar cartografia temàtica. A fi d'avaluar i reflexionar sobre les implicacions de la compressió, s'han cartografiat dues àrees amb diferents nivells de fragmentació espacial i dos tipus de paisatge principals: conreus i zones forestals. Cada una d'aquestes àrees s'ha analitzat utilitzant quatre escenes d'imatges Landsat i algunes variables topo-climàtiques. Els resultats mostren la influència de la compressió en la qualitat de la cartografia temàtica generada usant paràmetres quantitatius habituals (encert global i àrea classificada), així com consideracions visuals (modificació de l'efecte sal i pebre en la cartografia resultant)

Nou centre de dades d'observació de la Terra amb aplicacions innovadores

Els investigadors Alaitz Zabala i Xavier Pons, del Departament de Geografia de la UAB, i Joan Masó, del CREAF, participen en el projecte Next Generation GEOSS for Innovation Business (NextGEOSS) del programa Horizon 2020, per tal de posar en funcionament un centre de dades per a l'explotació de les dades d'observació de la Terra. En aquest article expliquen els principals objectius del projecte i com hi participa el grup de recerca GRUMETS.Los investigadores Alaitz Zabala y Xavier Pons, del Departamento de Geografía de la UAB, y Joan Masó, del CREAF, participan en el proyecto Next Generation GEOSS for Innovation Business (NextGEOSS) del programa Horizon 2020, para poner en funcionamiento un centro de datos para la explotación de los datos de observación de la Tierra. En este artículo explican los principales objetivos del proyecto y cómo participa el grupo de investigación GRUMETS.Researchers Alaitz Zabala and Xavier Pons, from UAB Geography Department, and Joan Masó, from CREAF, participate in Next Generation GEOSS for Innovation Business (NextGEOSS) Horizon 2020 project, to develop a centralised hub for Earth Observation data. In this article they explain the main project objectives as well as how GRUMETS research group contribute to them

New Model for Geospatial Coverages in JSON : Coverage Implementation Schema and Its Implementation With JavaScript

Map browsers currently in place present maps and geospatial information using common image formats such as JPEG or PNG, usually created from a service on demand. This is a clear approach for a simple visualization map browser but prevents the browser from modifying the visualization since the content of the image file represents the intensity of colors of each pixel. In a desktop GIS, a coverage dataset is an array of values quantifying a certain property in each pixel of a subdomain of the space. The standard used to describe and distribute coverages is called web coverage service (WCS). Traditionally, encoding of coverages was too complex for map browsers implemented in JavaScript, relegating the WCS to a data download, a process that creates a file that will be later used in a desktop GIS. The combination of a coverage implementation schema in JSON, binary arrays, and HTML5 canvas makes it possible that web map browsers can be directly implemented in JavaScript

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

Cartografía de usos y cubiertas del suelo del sureste de la Península Ibérica a partir de la clasificación de imágenes Landsat en el quinquenio 2000-2004

Se presenta la metodología utilizada en la obtención de la cartografía de usos y cubiertas del suelo para la zona oriental de Andalucía (ámbito de 29.259 km²) en el quinquenio 2000-2004, empleando el clasificador híbrido y utilizando imágenes Landsat junto con las variables auxiliares. Las áreas de entrenamiento se han obtenido de manera semiautomática a partir del SIOSE y depuradas con umbrales de NDVI. Se han ejecutado bancos de pruebas en función de las variables incluidas en el clasificador. Los mejores resultados, en cuanto a porcentaje de acierto y área clasificada,se han obtenido excluyendo la radiación 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%

Effects of JPEG and JPEG2000 lossy compression on remote sensing image classification for mapping crops and forest areas

This study measures the effect of lossy image compression on the digital classification of crops and forest areas. A hybrid classification method using satellite images and other variables has been used. The results contribute interesting new data on the influence of compression on the quality of the produced cartography, both from a "by pixel" perspective and regarding the homogeneity of the obtained polygons. The classified area in classifications only carried out with radiometric variables or with NDVI and humidity (for crops) increases as image compression increases, although the increase is smaller for JPEG2000 formats and for crops. On the other hand, the classified area decreases in classifications which also take into account topoclimatic variables (for forests). Overall image accuracy diminishes at high compression ratios (CR), although the point of inflection occurs at different CR depending on the compression format. As a rule, the JPEG2000 format gives better results quantitatively for forests (accuracy and classified area) and visually (images with less "salt and pepper" effect) for both land covers

Efectes de la compressió d'imatges en la generació de cartografia temàtica : avaluació en alguns casos de classificació digital

Els formats de compressió amb pèrdua permeten elevades raons de compressió amb una qualitat de la imatge notable per a raons de compressió moderades. Aquesta memòria de recerca pretén valorar la influència de la compressió amb pèrdua sobre la classificació digital sobre dos tipus d'usos del sòl (forestal i agrícola) i en dues àrees de diferents nivells de fragmentació per a cada us del sòl. L'àrea classificada augmenta a nivells de compressió elevats, especialment usant el format JPEG. L'encert de la classificació disminueix a nivells de compressió elevades. En general el format JPEG2000 dóna millors resultats que JPEG

Environmental and socioeconomic factors of abandonment of rainfed and irrigated crops in northeast Spain

Changes over the last century in the economic model of European countries and the development of the market economy have led to intense shifts in land occupation patterns. Agricultural abandonment is an important consequence of these processes and has modified natural and cultural landscapes, involving side-effects for society. Understanding how environmental and socio-economic factors influence the abandonment process can provide useful insights for managing investments, whether from the public or the private sector. In Spain, the Pyrenees and the Ebro Depression are two differentiated areas in terms of land-use dynamics, particularly in terms of the agricultural model carried out. In this paper we have analyzed the agricultural abandonment in these areas during the 1987-2012 period in relation to several potential explanatory factors. The analysis focuses on the abandonment of rainfed and irrigated herbaceous crops in order to derive specific explanations according to the crop type and geographical region. Crop covers were classified from four Landsat scenes, and conditions were described by topographic variables, human factors and drought occurrence. Boosted regression trees (BRT) were used to identify the most important variables and to describe the relationships between agricultural abandonment and key factors. Topography derived variables were found to be the main determinants, except for irrigated crops in the Ebro Basin, where locational factors play a more important role. BRT models allowed us to identify other significant patterns such as: the vulnerability of irrigated crops to drought; the higher dependence of agricultural activity in the Pyrenees on internal networks; pattern shifts of land abandonment in the analyzed sub-periods, and; evidence of the importance of economic diversification for maintaining cropland

Factors affecting forest dynamics in the Iberian Peninsula from 1987 to 2012 : the role of topography and drought

In southern Europe, climate trends are expected to be characterized by an increase in temperatures and less water availability. Analyzing the role of structural factors and the influence of a changing climate provides insights into the evolution of forest ecosystems in regions with similar environmental conditions. The Mediterranean fringe of the Iberian Peninsula is of particular interest due to its diverse topo climatic conditions and the increase in drought episodes during the last decades. This work studies forest dynamics in large areas of this geographical region by analyzing nine forest transitions. Vegetation covers were classified from three Landsat scenes for the period 1987-2012, and sub-periods 1987-2002 and 2002-2012. Conditions were described by topography derived variables, human factors and drought-occurrence variables. Boosted regression trees were used to identify the most important variables and describe the relationships between the forest dynamics and key factors. Variables such as solar radiation, topographic wetness index and tolerance to drought have been shown to be key factors in forest succession and when comparisons are made between vegetation groups. Main findings: The transition rate to Mediterranean and sub-Mediterranean broadleaf forests has increased during the analyzed period, while the transition rate to coniferous forests has decreased; Transitions to Mediterranean and sub-Mediterranean broadleaf forests are positively associated with drought occurrence while transitions to conifers are negatively affected by drought; Transitions from shrublands to forest stages are more vulnerable to factors controlling water availability; Important interactions between topography derived variables and drought have been found. The study provides robust evidence that drought occurrence plays an important role in the decline of conifers and the expansion of broadleaves, which could become the dominant species in many areas of the Mediterranean if climate model forecasts are met