Landscape dynamics of northeastern forests

This project involves collaborative research with Stephen W. Pacala and Simon A. Levin of Princeton University to calibrate, test, and analyze models of heterogeneous forested landscapes containing a diverse array of habitats. The project is an extension of previous, NASA-supported research to develop a spatially-explicit model of forest dynamics at the scale of an individual forest stand (hectares to square kilometer spatial scales). That model (SORTIE) has been thoroughly parameterized from field studies in the modal upland environment of western Connecticut. Under our current funding, we are scaling-up the model and parameterizing it for the broad range of upland environments in the region. Our most basic goal is to understand the linkages between stand-level dynamics (as revealed in our previous research) and landscape-level dynamics of forest composition and structure

Perspectives on earth resources mapping education in the United States

Este artículo describe el papel de la ASPRS en la enseñanza de la teledetección, fotogrametn'a y SIG. La forma para llevar a cabo este objetivo es resumir las actividades de cada una de las cinco Divisiones que estructuran la Sociedad, así como aquellas realizadas por los comités nacionales de la ASPRS. A su vez, este artículo trata de resaltar la necesidad de establecer un conjunto de estándars nacionales para la enseñanza y entrenamiento de la teledetección, sugiriendo el desarrollo de un «Curriculum Nuclear en teledetección», el cual estaría estructurado en tres fases distintas, pero interrelacionadas. Por otra parte, se sugieren una serie de cursos electivos para ampliar el curriculum nuclear en teledetección. Estos cursos serían superiores a las tres fases en las que se estructura dicho curriculum.This paper describes the education role of ASPRS in remote sensing, photogrammetry and GIS. A summary of Division and National Committees education and training activities is provided. It is enhanced the need to establish National standarsfor remote sensing education and training. The paper suggests an scenario for a «Remote Sensing Core Curriculum», which is structured in three distinct, yet interrelated, phases. The objective of these courses would be to produce qualifed remote sensing specialist. On the other hand, elective courses are suggested to improve this core curriculum. These courses would be above and beyond the three phases that structured the core curriculum

Perspectives on earth resources mapping education in the United States

Este artículo describe el papel de la ASPRS en la enseñanza de la teledetección, fotogrametn'a y SIG. La forma para llevar a cabo este objetivo es resumir las actividades de cada una de las cinco Divisiones que estructuran la Sociedad, así como aquellas realizadas por los comités nacionales de la ASPRS. A su vez, este artículo trata de resaltar la necesidad de establecer un conjunto de estándars nacionales para la enseñanza y entrenamiento de la teledetección, sugiriendo el desarrollo de un «Curriculum Nuclear en teledetección», el cual estaría estructurado en tres fases distintas, pero interrelacionadas. Por otra parte, se sugieren una serie de cursos electivos para ampliar el curriculum nuclear en teledetección. Estos cursos serían superiores a las tres fases en las que se estructura dicho curriculum.This paper describes the education role of ASPRS in remote sensing, photogrammetry and GIS. A summary of Division and National Committees education and training activities is provided. It is enhanced the need to establish National standarsfor remote sensing education and training. The paper suggests an scenario for a «Remote Sensing Core Curriculum», which is structured in three distinct, yet interrelated, phases. The objective of these courses would be to produce qualifed remote sensing specialist. On the other hand, elective courses are suggested to improve this core curriculum. These courses would be above and beyond the three phases that structured the core curriculum

Incorporating density in spatiotemporal land use/cover change patterns: The case of Attica, Greece

This paper looks at the periodic land use/cover (LUC) changes that occurred in Attica, Greece from 1991 to 2016. During this period, land transformations were mostly related to the artificial LUC categories; therefore, the aim was to map LUC with a high thematic resolution aimed at these specific categories, according to their density and continuity. The classification was implemented using the Random Forests (RF) machine learning algorithm and the presented methodological framework involved a high degree of automation. The results revealed that the majority of the expansion of the built-up areas took place at the expense of agricultural land. Moreover, mapping and quantifying the LUC changes revealed three uneven phases of development, which reflect the socioeconomic circumstances of each period. The discontinuous low-density urban fabric started to increase rapidly around 2003, reaching 7% (from 2.5% in 1991), and this trend continued, reaching 12% in 2016. The continuous as well as the discontinuous dense urban fabric, almost doubled throughout the study period. Agricultural areas were dramatically reduced to almost half of what they were in 1991, while forests, scrubs, and other natural areas remained relatively stable, decreasing only by 3% in 25 years

LULC Classification and Topographic Correction of Landsat-7 ETM+ Imagery in the Yangjia River Watershed: the Influence of DEM Resolution

DEM-based topographic corrections on Landsat-7 ETM+ imagery from rugged terrain, as an effective processing techniques to improve the accuracy of Land Use/Land Cover (LULC) classification as well as land surface parameter retrievals with remotely sensed data, has been frequently reported in the literature. However, few studies have investigated the exact effects of DEM with different resolutions on the correction of imagery. Taking the topographic corrections on the Landsat-7 ETM+ images acquired from the rugged terrain of the Yangjiahe river basin (P.R. China) as an example, the present work systematically investigates such issues by means of two commonly used topographic correction algorithms with the support of different spatial resolution DEMs. After the pre-processing procedures, i.e. atmospheric correction and geo-registration, were applied to the ETM+ images, two topographic correction algorithms, namely SCS correction and Minnaert correction, were applied to assess the effects of different spatial resolution DEMs obtained from two sources in the removal of topographic effects and LULC classifications. The results suggested that the topographic effects were tremendously reduced with these two algorithms under the support of different spatial resolution DEMs, and the performance of the topographic correction with the 1:50,000-topographic-map DEM was similar to that achieved using SRTM DEM. Moreover, when the same topographic correction algorithm was applied the accuracy of LULC classification after topographic correction based on 1:50,000-topographic-map DEM was similar as that based on SRTM DEM, which implies that the 90 m SRTM DEM can be used as an alternative for the topographic correction of ETM+ imagery when high resolution DEM is unavailable

Spectral Pattern Recognition by a Two-Layer Perceptron: Effects of Training Set Size

Pattern recognition in urban areas is one of the most challenging issues in classifying satellite remote sensing data. Parametric pixel-by-pixel classification algorithms tend to perform poorly in this context. This is because urban areas comprise a complex spatial assemblage of disparate land cover types - including built structures, numerous vegetation types, bare soil and water bodies. Thus, there is a need for more powerful spectral pattern recognition techniques, utilizing pixel-by-pixel spectral information as the basis for automated urban land cover detection. This paper adopts the multi-layer perceptron classifier suggested and implemented in [5]. The objective of this study is to analyse the performance and stability of this classifier - trained and tested for supervised classification (8 a priori given land use classes) of a Landsat-5 TM image (270 x 360 pixels) from the city of Vienna and its northern surroundings - along with varying the training data set in the single-training-site case. The performance is measured in terms of total classification, map user's and map producer's accuracies. In addition, the stability with initial parameter conditions, classification error matrices, and error curves are analysed in some detail. (authors' abstract)Series: Discussion Papers of the Institute for Economic Geography and GIScienc

The complex X-ray spectrum of NGC 4507

XMM-Newton and Chandra/HETG spectra of the Compton-thin (NH 4x10^{23} cm^{-2}) Seyfert 2 galaxy, NGC 4507, are analyzed and discussed. The main results are: a) the soft X-ray emission is rich in emission lines; an (at least) two--zone photoionization region is required to explain the large range of ionization states. b) The 6.4 keV iron line is likely emitted from Compton-thick matter, implying the presence of two circumnuclear cold regions, one Compton-thick (the emitter), one Compton-thin (the cold absorber). c) Evidence of an Fe xxv absorption line is found in the Chandra/HETG spectrum. The column density of the ionized absorber is estimated to be a few x10^{22} cm^{-2}.Comment: accepted for publication in A&