Hydrologic and geologic control of carbonate water chemistry in the subarctic nahanni karst,canada     

George A. Brook  Derek C. Ford 《地球表面变化过程与地形》1982,7(1):1-16

There are six classes of water and five geologic environments in the subarctic Nahanni karst. During the summers of 1972 and 1973, 214 water samples were collected from 15 of the 30 hydrogeologic categories. Linear discriminant function analysis, using five measured and two derived chemical variables, indicates that there are statistically significant (0.005 level) differences in water chemistry between similar waters in different geologic environments, between waters in the same geologic environment, and between waters in different hydrogeological categories. Geological environment labels a natural water because it determines the availability of soil CO₂ and of soluble minerals. Measurements indicate that mean soil log PCO₂ is greatest in areas of shale mantled by till (?2.39), and least in areas of sandy fluvioglacial drift (?3.27). Low values on the sandy drift are due to the sparse shrub vegetation, and to the high degree of soil aeration; soils in areas of shale are clay-rich and support a dense boreal forest. Hydrology influences water chemistry because it determines how much CO₂ natural waters pick up from the environment and how much they subsequently lose to the atmosphere, and as a result, whether they dissolve or deposit soluble materials. The similarity between mean calculated log PCO₂ in natural waters (?2.92) and mean measured soil log PCO₂ (?2.80) suggests that natural waters in Nahanni are dose to equilibrium with mean soil CO₂ levels.  相似文献   

对应分析约束下的重磁联合反演及其在塔里木盆地的应用   总被引：2，自引：3，他引：2       下载免费PDF全文

黎益仕  殷秀华 《地震地质》1996,18(4):361-368

综合应用重磁对应分析和重磁联合反演的基础上提出对重磁联合反演的一种改进方法：约束联合反演，即利用重磁异常相关系数对联合反演中目标函数进行加权。实验结果表明，该方法有利于迭代反演的收敛性。把该方法应用于塔里木盆地东部库尔勒～若羌剖面，结果说明，以对应分析的结果作为先验认识，有助于合理地建立最优化反演的初始模型，能提高解释结果的质量  相似文献   

非量测相机摄影测量的整体平差   总被引：1，自引：0，他引：1  

李全海 《测绘工程》1996,5(1):32-35

论述了整体平差处理非量测相机摄影测量问题的计算模型，并对一些实例进行了解算。通过实例解算结果的分析比较，获得一些有益的结论。  相似文献   

Sub-pixel classification of SPOT-VEGETATION time series for the assessment of regional crop areas in Belgium   总被引：1，自引：0，他引：1  

Sara Verbeiren  Herman Eerens  Isabelle Piccard  Ides Bauwens  Jos Van Orshoven 《International Journal of Applied Earth Observation and Geoinformation》2008,10(4):486

Global time series of low resolution images are available with high repeat frequency and at low cost, but their analysis is hampered by the presence of mixed pixels and the difficulty in locating detailed spatial features. This study examined the potential of sub-pixel classification for regional crop area estimation using time series of monthly NDVI-composites of the 1 km resolution sensor SPOT-VEGETATION. Belgium was selected as test zone, because of the availability of ample reference data in the form of a vectorial GIS with the boundaries and cover type of the large majority of agricultural fields. Two different methods were investigated: the linear mixture model and neural networks. Both result in area fraction images (AFIs), which contain for each 1 km pixel the estimated area proportions occupied by the different cover types (crops or other land use). Both algorithms were trained with part of the reference data and validated with the remainder. Validation was repeated at three different levels: the 1 km pixel, the municipality and the agro-statistical district. In general, the neural network outperformed the linear mixture model. For the major classes (winter wheat, maize, forest) the obtained acreage estimates showed good agreement with the true values, especially when aggregated to the level of the municipality (R² ≈ 85%) or district (R² ≈ 95%). The method seems attractive for wide-scale, regional area estimation in data-poor countries.  相似文献   

Street as a big geo-data assembly and analysis unit in urban studies: A case study using Beijing taxi data     

《Applied geography (Sevenoaks, England)》2017

Quantitative research of urban geography has benefited greatly from the rapid development of big geo-data. Spatial assembly is an essential analytical step to summarize and perceive geographical environment from individual behaviours. Most research focuses on the methodology of how to utilize the big data, while the adopted spatial units for data aggregation remain areal in nature. This article conceptually proposes an idea of sensing cities from a street perspective, emphasizes the significance of street units in quantitative urban studies. Using a three-month taxi trajectory dataset and the major streets in Beijing, we explore the spatio-temporal patterns of urban mobility on streets, cluster streets into nine types based on their dynamic functions and capacities. Additionally, we discuss the differences and connections between the linear street unit and traditional areal units, investigate the possibility of uncovering urban communities using streets, and point out the complexity of streets. We conclude that street unit as a supplement to areal units, is able to effectively minify the modifiable areal unit problem (MAUP), sense urban dynamics, depict urban functions, and understand urban structures.  相似文献   

Automated mapping of impervious surfaces in urban and suburban areas: Linear spectral unmixing of high spatial resolution imagery     

《International Journal of Applied Earth Observation and Geoinformation》2017

Quantifying impervious surfaces in urban and suburban areas is a key step toward a sustainable urban planning and management strategy. With the availability of fine-scale remote sensing imagery, automated mapping of impervious surfaces has attracted growing attention. However, the vast majority of existing studies have selected pixel-based and object-based methods for impervious surface mapping, with few adopting sub-pixel analysis of high spatial resolution imagery. This research makes use of a vegetation-bright impervious-dark impervious linear spectral mixture model to characterize urban and suburban surface components. A WorldView-3 image acquired on May 9th, 2015 is analyzed for its potential in automated unmixing of meaningful surface materials for two urban subsets and one suburban subset in Toronto, ON, Canada. Given the wide distribution of shadows in urban areas, the linear spectral unmixing is implemented in non-shadowed and shadowed areas separately for the two urban subsets. The results indicate that the accuracy of impervious surface mapping in suburban areas reaches up to 86.99%, much higher than the accuracies in urban areas (80.03% and 79.67%). Despite its merits in mapping accuracy and automation, the application of our proposed vegetation-bright impervious-dark impervious model to map impervious surfaces is limited due to the absence of soil component. To further extend the operational transferability of our proposed method, especially for the areas where plenty of bare soils exist during urbanization or reclamation, it is still of great necessity to mask out bare soils by automated classification prior to the implementation of linear spectral unmixing.  相似文献   

Estimating fractional vegetation cover and the vegetation index of bare soil and highly dense vegetation with a physically based method     

《International Journal of Applied Earth Observation and Geoinformation》2017

Normalized difference vegetation index (NDVI) of highly dense vegetation (NDVI_v) and bare soil (NDVI_s), identified as the key parameters for Fractional Vegetation Cover (FVC) estimation, are usually obtained with empirical statistical methods However, it is often difficult to obtain reasonable values of NDVI_v and NDVI_s at a coarse resolution (e.g., 1 km), or in arid, semiarid, and evergreen areas. The uncertainty of estimated NDVI_s and NDVI_v can cause substantial errors in FVC estimations when a simple linear mixture model is used. To address this problem, this paper proposes a physically based method. The leaf area index (LAI) and directional NDVI are introduced in a gap fraction model and a linear mixture model for FVC estimation to calculate NDVI_v and NDVI_s. The model incorporates the Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) model parameters product (MCD43B1) and LAI product, which are convenient to acquire. Two types of evaluation experiments are designed 1) with data simulated by a canopy radiative transfer model and 2) with satellite observations. The root-mean-square deviation (RMSD) for simulated data is less than 0.117, depending on the type of noise added on the data. In the real data experiment, the RMSD for cropland is 0.127, for grassland is 0.075, and for forest is 0.107. The experimental areas respectively lack fully vegetated and non-vegetated pixels at 1 km resolution. Consequently, a relatively large uncertainty is found while using the statistical methods and the RMSD ranges from 0.110 to 0.363 based on the real data. The proposed method is convenient to produce NDVI_v and NDVI_s maps for FVC estimation on regional and global scales.  相似文献   

线性准地转模型中副热带感热加热强迫的定常波          下载免费PDF全文

张亚妮  刘屹岷  吴国雄  姚秀萍 《Acta Meteorologica Sinica》2016,74(6):889-901

通过求取定常线性准地转位涡模式的解析解,研究了感热加热强迫所激发的副热带定常波的结构特征,讨论了基本流、牛顿冷却及地面摩擦等对定常波振幅和位相的影响。结果表明,东风时定常波在垂直方向上表现为上、下层反位相的第一斜压结构,且地面系统远强于中高层;西风时定常波呈现出向上的传播特征,在高层,随着风速增大振幅随高度的升高有增大趋势。在近地层,东风时气旋（反气旋）主体位于加热西（东）侧;西风时气旋（反气旋）主体位于加热东（西）侧,近地层以上相反。此外,发现东、西风基本流的作用具有对称特征,这与潜热加热显著不同。研究结果还表明,牛顿冷却对定常波有重要影响,基本流越弱影响越显著。在静止大气中,感热加热强迫下无斯韦尔德鲁普（Sverdrup）解,考虑牛顿冷却时,感热强迫在热源范围内的近地层和中高层分别激发出气旋式和反气旋式环流,气旋中心位于加热中心略偏西的位置。在非静止大气中,牛顿冷却项使地面系统中心向上风方向移动,东风时向东移。牛顿冷却对高、低层系统均有削弱作用。地面摩擦则明显不同,它总会使低层系统减弱,高层系统增强。  相似文献   

计算机代数实验课程初探     

薛长虹 《成都信息工程学院学报》1998,(4)

从高等院校数学课程教学模式的探讨入手,提出了数学课与计算机实验相结合的改革思想,并通过实践对开设数学实验课各个环节的合理定位作了详细的描述,主要采用Ｍａｔｌａｂ软件作为线性代数实验课的实验工具,辅助理论教学,开设数学实验课,并对开设实验课后的成效及尚存的问题进行了剖析。  相似文献   

线性四叉树和线性八叉树邻域寻找的一种新算法   总被引：26，自引：0，他引：26  

肖乐斌  龚建华  谢传节 《测绘学报》1998,27(3):195-203

线性四叉树和线性八叉树邻域寻找的一种新算法肖乐斌①龚建华②谢传节①（①中国科学院地理研究所资源与环境信息系统国家重点实验室,北京,１００１０１）（②香港中文大学地理系地球信息科学联合实验室,香港）ＡＮＥＷＡＬＧＯＲＩＴＨＭＦＯＲＳＥＡＲＣＨＩＮＧＮＥ...  相似文献