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Modeling the Uncertainty of Slope and Aspect Estimates Derived from Spatial Databases 总被引:1,自引:0,他引:1
Estimates of slope and aspect are commonly made from digital elevation models (DEMs), and are subject to the uncertainty present in such models. We show that errors in slope and aspect depend on the spatial structure of DEM errors. We propose a general-purpose model of DEM errors in which a spatially auto-regressive random field is added as a disturbance term to elevations. In addition, we propose a general procedure for propagating such errors through GIS operations. In the absence of explicit information on the spatial structure of DEM errors, we demonstrate the potential utility of a worst-case analysis. A series of simulations are used to make general observations about the nature and severity of slope and aspect errors. 相似文献
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Gary Simon 《Geographical analysis》1997,29(3):267-278
Spatial correlations are replaced by ordinary correlations by projecting the two-dimensional coordinates of a map onto a single axis making angle θ with the horizontal (east-west) axis. This calculation permits the use of exact test statistics. Moreover, the correlations can be plotted in polar coordinate form and the significance of the maximum correlation can be tested. The plot is a useful aid in assessing the reasonableness of the isotropy assumption. 相似文献
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Gary Smith 《Australian Journal of International Affairs》2010,64(5):566-582
Australia is at risk of being left behind by the pace of India's emergence as a regional and global power and its lack of engagement with India during this emergence. The Rudd Labor government is developing a framework which may make Australia a significant partner with India. There is the potential for a thoroughgoing engagement of interests and ideals in proposals Australia has put forward in three areas. Australia's vision of an Asia Pacific Community, with cooperation as its habitual operating principle, and with a membership that includes India and the USA as well as China and Japan, fills a multilateral gap. Secondly, the International Commission on Nuclear Non-Proliferation and Disarmament may provide a global framework assisting the development of Australian and Indian initiatives in the controlling and winding back of nuclear proliferation. Thirdly, Australia's national carbon pollution reduction program is intended to demonstrate international leadership and engagement in climate change, and opens the prospect for Australia of a substantial bilateral partnership with India (and others) to advance common interests around climate change. Australia, while emphasising its close relationship with the USA, is preparing to live in a region where the USA will, over time, be less influential as its relative power declines. As other great powers rise, Australia can actively pursue a hedging strategy to diversify its dependencies, and develop a much deeper engagement with that other emerging Asian giant. 相似文献
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Recent years have witnessed a proliferation of state government policies addressing immigration‐related issues. This article addresses an example of state policy regarding immigration: since 2001, 11 state legislatures have granted undocumented high school graduates in‐state tuition status should they wish to attend public post‐secondary schools, while 18 others have considered, and rejected, the same policy. We argue that these outcomes are largely explicable by the manner in which the policy is presented and debated within state legislatures, especially the terms in which policy targets are socially constructed and state jurisdictional authority is framed. We apply this framework to two states (Kansas and Arkansas) that, in spite of demographic institutional similarities, reached different outcomes on in‐state tuition bills. The different outcomes can be traced to the manner in which policy deliberations in Kansas focused on positive evaluations of undocumented high school students, portraying them as “proto‐citizens,” while in Arkansas debate became centered on the state's jurisdictional authority to enact such a policy, an issue frame that effectively killed the legislation. This article suggests the importance of both social constructions and issue framing when state legislatures become the lead actors in crafting immigration policies. 相似文献
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Don?Hein Gary?HillEmail author W.?Ross?H.?Ramsay 《International Journal of Historical Archaeology》2004,8(4):247-266
Sawankhalok, located in north central Thailand, was an early stoneware ceramic production site where the first kilns were dug cave-like into the natural ground, a method used in China for thousands of years. After a century or so, kilns at Sawankhalok began to be constructed of brick. It is suggested that if the bricks were pre-fired then an external influence may have been responsible. To the contrary, if raw unfired clay was used in the construction of the kilns the evolution was more likely a consequence of conceptual continuity.With the aid of chemical and mineralogical analyses it is shown that the kiln bricks were unfired at the time of kiln construction thereby suggesting that traditional conservatism, apparent in many aspects of the industry, caused processes to remain unaltered in the absence of a persuasive reason for change. These conclusions reflect on the degree of indigenous technology and artistic development associated with Sawankhalok ceramics as opposed to external influence. 相似文献
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