Converting local spectral and spatial information from a priori classifiers into contextual knowledge for impervious surface classification     

Li LuoGiorgos Mountrakis 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(5):579-587

A classification model was demonstrated that explored spectral and spatial contextual information from previously classified neighbors to improve classification of remaining unclassified pixels. The classification was composed by two major steps, the a priori and the a posteriori classifications. The a priori algorithm classified the less difficult image portion. The a posteriori classifier operated on the more challenging image parts and strived to enhance accuracy by converting classified information from the a priori process into specific knowledge. The novelty of this work relies on the substitution of image-wide information with local spectral representations and spatial correlations, in essence classifying each pixel using exclusively neighboring behavior. Furthermore, the a posteriori classifier is a simple and intuitive algorithm, adjusted to perform in a localized setting for the task requirements. A 2001 and a 2006 Landsat scene from Central New York were used to assess the performance on an impervious classification task. The proposed method was compared with a back propagation neural network. Kappa statistic values in the corresponding applicable datasets increased from 18.67 to 24.05 for the 2006 scene, and from 22.92 to 35.76 for the 2001 scene classification, mostly correcting misclassifications between impervious and soil pixels. This finding suggests that simple classifiers have the ability to surpass complex classifiers through incorporation of partial results and an elegant multi-process framework.  相似文献   

南京市区不同下垫面对近地层温度影响   总被引：1，自引：1，他引：0  

裴海瑛  姜爱军  叶香 《气象科学》2011,31(6):777-783

利用南京市内设立在4种不同典型下垫面的自动气象观测站逐时温度资料,采用对比分析方法,分析不同下垫面对城市近地层温度的影响.结果表明,城市绿地在日出日落后温度变化最明显,春秋两季温度变化速率超过2℃/h,夏冬两季也可达1.2℃/h,这使得绿地夜晚温度较低;城市水体日出日落后的温度变化速率最小,因而城市水体夜晚温度较高,尤其在春秋两季最为明显;城市中的生活区和校区在日出日落后温度变化速率稍高于城市水体,夜间温度一般高于绿地,低于水体.另外,不同下垫面对城市气温的季节变化也有影响,城市水体秋冬季节温度高,绿地在夏季温度低,使得温度的平均年变化减小;城市生活区和校区温度的季节变化特征与前两者相反.温度年变化在四季转换过程中的不均匀性在不同下垫面上也有不同的特点,在冬半年,城市水体温度的月际变化较大,而绿地月际变化小,夏半年则出现完全相反的情况.  相似文献   

Spectral study of the Eunomia asteroid family : I. Eunomia     

Andreas Nathues  Stefano Mottola  Gerhard Neukum 《Icarus》2005,175(2):452-463

We present color ratio curves of the S-Asteroid 15 Eunomia, which have been extracted from high-precision photometric lightcurves obtained in three different VNIR wavelength bands at the Bochum Telescope, La Silla. The measured color ratio curves and near infrared spectra were used to derive a detailed surface composition model whose shape has been computed by V-lightcurve inversions. According to this analysis, the asteroid shows on one hemisphere a higher concentration of pyroxene, which causes an increased 440/700 nm and a reduced 940/700 nm reflectance ratio as well as a pronounced 2-μm absorption band. The remaining surface shows a higher concentration of olivine, leading to a reduced 440/700 nm and slightly increased 940/700 nm color ratio. In addition, we found that the maximum of the 440/700 nm color ratio curve coincide with the minimum of the 940/700 nm color ratio curve and vice versa. We demonstrate on the basis of USGS laboratory spectra that this anti-cyclical behavior can be explained by choosing Fe-rich olivine and a pyroxene with moderate Fe content as varying mineral phases. Furthermore, our observations confirm that 15 Eunomia is an irregular elongated and at least partially differentiated body. Previous spectral investigations of several smaller fragments of the Eunomia asteroid family revealed that the amount of fragments showing an increased pyroxene content exceeds the amount of pyroxene-poor fragments (Nathues, 2000, DLR Forschungsbericht, ISSN 1434-8454). This finding together with the observation that the major fraction of Eunomia's surface is enriched in olivine let us claim that a large fraction of the original pyroxene-enriched crust layer has been lost due to a major collision that created the Eunomia asteroid family. Significant spectral evidences, consistent with high concentrations of metals have been found neither in the rotational resolved spectra of 15 Eunomia nor in its fragments. This led to the conclusion that either no core consisting mainly of metals exists or that an eventual one has not been unearthed by the impact.  相似文献   

Frictional contact of laminated elastic half‐spaces allowing interface cavities. Part 2: Numerical results     

A. A. Kryshtafovych  S. J. Matysiak 《国际地质力学数值与分析法杂志》2001,25(11):1089-1099

The paper presents some numerical results of the problem on contact of stratified elastic half‐spaces possessing unevenness of their surface layers. The approach of the Jacobi polynomials is used to reduce the singular integral equation of the problem to a system of linear algebraic equations. On the basis of the system's solution the dependence of gaps' geometric characteristics on external load and friction is investigated for two types of initial boundary disturbances, namely a local symmetric recess and a periodic set of recesses at a flat boundary. Numerical results are presented in figures for a few elastic and geometric parameters of joint components. The analysis shows that elastic properties and geometric structure of a laminated half‐space have a significant influence on the shape of interface gaps and their location. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

地带性与非地带性夷平面^*   总被引：6，自引：0，他引：6  

张信宝  周力平  汪阳春  吴积善  贺秀斌  齐永青 《第四纪研究》2007,27(1):93-99

夷平面是指由剥蚀和夷平作用所产生的,以截面形式横切所有在年龄上先于它的地层和构造的一种平缓地形。前人普遍认为,夷平面是在构造相对稳定条件下经过长期外营力作用形成的一个接近基准面的平坦地形,是地貌长期演化的终极产物。 流水侵蚀是夷平面形成的动力学基础。"夷平面"一直是解释新生代以来大的构造格局和地貌演化的重要理论依据,如我国青藏高原隆升的研究。 基于气候地貌学原理,文章提出了寒冻夷平面和干旱夷平面的概念;从坡地演化过程理论模型入手,探讨了寒冻、干旱夷平面和流水夷平面的形成机理;提出有别于传统"构造侵蚀旋迴"理论的"构造隆升和地面剥夷动态平衡"的气候夷平地貌假说;此外,还简要分析了这三类夷平面的全球分布规律。  相似文献   

三维激光扫描技术与断层面形貌量化分析在基岩区古地震研究中的应用     

邹俊杰  何宏林  耿爽  石峰  周永胜  孙稳 《震灾防御技术》2022,17(1):56-67

由于对第四纪地层的严重依赖,传统古地震探槽研究方法在基岩区难以发挥作用,导致无法获取基岩区断层的强震活动历史。本研究以山西地堑系的交城断裂为目标断裂,以断裂北段2处基岩断层面为研究对象,通过三维激光扫描技术获取基岩断层面高精度形貌,基于变差函数法结合滑动窗口操作量化断层表面形貌特征,开展在基岩区提取断裂古地震信息的实例研究。结果显示,2处基岩断层面的形貌在高度上具有明显的分段特征,指示了断层面在地震事件作用下的分段出露过程。这种断层面形貌分段特征可以用来识别古地震事件和同震位移量。在思西村基岩断层面上,识别出由老到新的3次古地震事件,同震倾滑位移量依次为2.0 m、1.9 m和2.3 m,在上兰镇基岩断层面上,识别出由老到新的3次古地震事件,同震倾滑位移量依次为1.4 m、2.5 m和2.0 m,指示了交城断裂北、中段具有产生同震位移量大于2 m、震级大于7.5级的破裂型地震的能力。上述研究成果表明,基于三维激光扫描和形貌量化分析方法开展基岩断层面古地震研究,可以准确而高效地识别古地震事件次数和同震位移量,扩展古地震的研究对象,拓宽古地震的研究空间。在未来的研究中,可以适时地开展宇宙成因核素测年以测定断层面的暴露年龄,获得发震年代,给予地震序列年龄框架。  相似文献   

The radiolysis of SO₂ and H₂S in water ice: Implications for the icy jovian satellites     

M.H. Moore  R.L. Hudson 《Icarus》2007,189(2):409-423

Spectra of Europa, Ganymede, and Callisto reveal surfaces dominated by frozen water, hydrated materials, and minor amounts of SO₂, CO₂, and H₂O₂. These icy moons undergo significant bombardment by jovian magnetospheric radiation (protons, electrons, and sulfur and oxygen ions) which alters their surface compositions. In order to understand radiation-induced changes on icy moons, we have measured the mid-infrared spectra of 0.8 MeV proton-irradiated SO₂, H₂S, and H₂O-ice mixtures containing either SO₂ or H₂S. Samples with H₂O/SO₂ or H₂O/H₂S ratios in the 3-30 range have been irradiated at 86, 110, and 132 K, and the radiation half-lives of SO₂ and H₂S have been determined. New radiation products include the H₂S₂ molecule and HSO⁻₃, HSO⁻₄, and SO²⁻₄ ions, all with spectral features that make them candidates for future laboratory work and, perhaps, astronomical observations. Spectra of both unirradiated and irradiated ices have been recorded as a function of temperature, to examine thermal stability and phase changes. The formation of hydrated sulfuric acid in irradiated ice mixtures has been observed, along with the thermal evolution of hydrates to form pure sulfuric acid. These laboratory studies provide fundamental information on likely processes affecting the outer icy shells of Europa, Ganymede, and Callisto.  相似文献   

Optical ages on loess derived from outwash surfaces constrain the advance of the Laurentide Ice Sheet out of the Lake Superior Basin,USA     

Randall J. Schaetzl  Steven L. Forman  John W. Attig 《Quaternary Research》2014

We present textural and thickness data on loess from 125 upland sites in west-central Wisconsin, which confirm that most of this loess was derived from the sandy outwash surfaces of the Chippewa River and its tributaries, which drained the Chippewa Lobe of the Laurentide front during the Wisconsin glaciation (MIS 2). On bedrock uplands southeast of the widest outwash surfaces in the Chippewa River valley, this loess attains thicknesses > 5 m. OSL ages on this loess constrain the advance of the Laurentide ice from the Lake Superior basin and into west-central Wisconsin, at which time its meltwater started flowing down the Chippewa drainage. The oldest MAR OSL age, 23.8 ka, from basal loess on bedrock, agrees with the established, but otherwise weakly constrained, regional glacial chronology. Basal ages from four other sites range from 13.2 to 18.5 ka, pointing to the likelihood that these sites remained geomorphically unstable and did not accumulate loess until considerably later in the loess depositional interval. Other OSL ages from this loess, taken higher in the stratigraphic column but below the depth of pedoturbation, range to nearly 13 ka, suggesting that the Chippewa River valley may have remained a loess source for several millennia.  相似文献   

On the chemical composition of Titan’s dry lakebed evaporites     

D. Cordier  J.W. Barnes  A.G. Ferreira 《Icarus》2013

Titan, the main satellite of Saturn, has an active cycle of methane in its troposphere. Among other evidence for a mechanism of evaporation at work on the ground, dry lakebeds have been discovered. Recent Cassini infrared observations of these empty lakes have revealed a surface composition poor in water ice compared to that of the surrounding terrains—suggesting the existence of organic evaporites deposits. The chemical composition of these possible evaporites is unknown. In this paper, we study evaporite composition using a model that treats both organic solids dissolution and solvent evaporation. Our results suggest the possibility of large abundances of butane and acetylene in the lake evaporites. However, due to uncertainties of the employed theory, these determinations have to be confirmed by laboratory experiments.  相似文献   

Facets of uncertainty in digital elevation and slope modeling     

Zhang Jingxiong  Li Deren 《地球空间信息科学学报》2013,16(3):163-170

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