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Peter M. Atkinson 《International Journal of Applied Earth Observation and Geoinformation》2004,5(4):277-291
A simple approach for incorporating a spatial weighting into a supervised classifier for remote sensing applications is presented. The classifier modifies the feature-space distance-based metric with a spatial weighting. This is facilitated by the use of a non-parametric (k-nearest neighbour, k-NN) classifier in which the spatial location of each pixel in the training data set is known and available for analysis. A remotely sensed image was simulated using a combined Boolean and geostatistical unconditional simulation approach. This simulated image comprised four wavebands and represented three classes: Managed Grassland, Woodland and Rough Grassland. This image was then used to evaluate the spatially weighted classifier. The latter resulted in modest increase in the accuracy of classification over the original k-NN approach. Two spatial distance metrics were evaluated: the non-centred covariance and a simple inverse distance weighting. The inverse distance weighting resulted in the greatest increase in accuracy in this case. 相似文献
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The neoliberalization of ecosystem services: wetland mitigation banking and problems in environmental governance 总被引:1,自引:0,他引:1
Morgan M. Robertson 《Geoforum》2004,35(3):361-373
Wetland mitigation banking is an American neoliberal environmental policy that has created a functioning market in `ecosystem services', commodities defined using the holistic measures of ecological science. The development of this market is discussed as a project of environmental governance, defined as the nation-state's regulation of ecological relations within its territory towards stabilizing capitalist relations of power and accumulation. I argue that the wetland banking industry serves as a bellwether that presages problems that other strategies of neoliberal environmental governance will experience. Ethnographic, economic and ecological data from the Chicago-area wetland banking industry inform a discussion of two major obstacles to neoliberal strategy: the problem of relying on ecological science to define the unit of trade, and the problem of aligning the somewhat independent relations of law, politics, markets and ecosystems across an array of spatial scales. Theoretical guidance is sought from recent work on `social natures' and from the Regulationist approach to institutional political economics. 相似文献
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3维数据模型的建立是实现真3维GIS的一个核心问题。在充分分析现有3维数据模型的基础上,比较了传统模型的优缺点。针对空间目标建模的特点,设计了一种面向对象的3维数据模型。考虑到软件的实用性和可扩展性,着重论述了3维交互式设计及数据管理。 相似文献
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In this paper, we discuss the development of electronic atlas in China, with focus on the issues of visualization. We particularly categorise this development into four periods, and then analyse the characters in each period and discuss the visualization issues. The four periods are highlighted: 1) Infant period (<1990) characterized as computer assisted mapping with products of screen maps; 2) Starting period (1991-1995) characterized as object-oriented mapping with products of interactive maps/atlases; 3) Advancing period (1996-2000) characterized as integrated mapping with products of multimedia cartographic maps; 4) New era (> 2001) characterized as web mapping and adaptive map design with products of Internet maps and atlas as well as adaptive maps. It is obvious that the development follows the logical way from static to dynamic, and even real time visualization, from single user to multiple users, from presentation to exploration for effective communication and knowledge construction. Current research and development projects are focused on customisation of atlas information systems for real-time tasks, Internet operability, small displays and mobile environments. The major challenges involved in each of such customisation processes are identified and commented in relation to the further development of visualization. 相似文献
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Mohammad M. Sohrabi Rohan Benjankar Daniele Tonina Seth J. Wenger Daniel J. Isaak 《水文研究》2017,31(9):1719-1733
Stream water temperature plays a significant role in aquatic ecosystems where it controls many important biological and physical processes. Reliable estimates of water temperature at the daily time step are critical in managing water resources. We developed a parsimonious piecewise Bayesian model for estimating daily stream water temperatures that account for temporal autocorrelation and both linear and nonlinear relationships with air temperature and discharge. The model was tested at 8 climatically different basins of the USA and at 34 sites within the mountainous Boise River Basin (Idaho, USA). The results show that the proposed model is robust with an average root mean square error of 1.25 °C and Nash–Sutcliffe coefficient of 0.92 over a 2‐year period. Our approach can be used to predict historic daily stream water temperatures in any location using observed daily stream temperature and regional air temperature data. 相似文献
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Most of previous analyses on the active earth pressure were performed in two-dimensional cases using the Mohr-Coulomb (M-C) failure function to describe the soil strength. However, all failures of retained slopes indicate a somewhat three-dimensional (3D) feature, and the M-C function is found to overestimate the tensile strength of cohesive soil. In this work, a kinematic limit analysis–based approach is developed for computing the 3D active earth pressure resulting from cohesive backfills. The concept of tensile strength cutoff is adopted to implement the reduction or elimination of tensile strength from the strength envelope. An extended 3D horn failure mechanism that is associated with the modified strength envelope is developed to characterize the collapse of retained slopes. The resultant of active earth pressure is evaluated from the work rate balance equation and expressed as an unfactored coefficient. The obtained results indicate that less support provided by the wall is required when allowing the existence of soil cohesion and 3D effects and that eliminating the tensile strength can observably increase the active earth pressure, especially for the backfill with a great level of cohesion. 相似文献
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For civil engineering structures with a tightness role, structural permeability is a key issue. In this context, this paper presents a new proposition of a numerical modelling of leakage rate through a cracked concrete structure undergoing mode I cracking. The mechanical state of the material, considered in the framework of continuum mechanics based on finite element modelling, is described by means of the stress‐based nonlocal damage model which takes into account the stress state and provides realistic local mechanical fields. A semi‐discrete method based on the strong discontinuity approach to estimate crack opening is then considered in the post‐treatment phase. Using a Poiseuille's like relation, the coupling between the mechanical state of the material and its dry gas conductivity is performed. For validation purposes, an original experimental campaign is conducted on a dry concrete disc loaded in a splitting setup. During the loading, gas conductivity and digital image correlation analysis are performed. The comparison with the 3D experimental mechanical global response highlights the performance of the mechanical model. The comparison between crack openings measured by digital image correlation and estimated by the strong discontinuity method shows a good agreement. Finally, the results of the semi‐discrete approach coupled with the gas conductivity compared with experimental data show a good estimation of the structural conductivity. Consequently, if the mechanical problem is well modelled at the global scale, then the proposed approach provides good estimation of gas conductivity. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献