中国上市公司的时空变化及机制研究     

李黎  李成名  戴昭鑫  吴政  满旺 《测绘科学》2019,44(6):324-329,336

针对在中国地区发展不均衡的态势下,上市公司分布格局时空演变问题,该文对2009-2017年中国大陆各省上市公司的数量和总资产采用Local Moran’s I指数与Getis-Ord Gi*统计量进行研究,分析了中国大陆上市公司的空间分布格局和时间演变趋势,总结出中国上市公司相关指标的高值聚集和高低聚集分布格局、热点区域及其经济辐射能力。并且以北京、上海和广东为热点区域典型代表,从上市公司产业结构和区域经济发展两方面对时空变化机制的成因进行深入探讨。  相似文献   

Simulation of landscape spatial layout evolution in rural-urban fringe areas: a case study of Ganjingzi District   总被引：2，自引：0，他引：2  

Jun Yang  Andong Guo  Yonghua Li  Yuqing Zhang  Xueming Li 《地理信息系统科学与遥感》2019,56(3):388-405

In recent years, the rapid expansion of urban spaces has accelerated the mutual evolution of landscape types. Analyzing and simulating spatio-temporal dynamic features of urban landscape can help to reveal its driving mechanisms and facilitate reasonable planning of urban land resources. The purpose of this study was to design a hybrid cellular automata model to simulate dynamic change in urban landscapes. The model consists of four parts: a geospatial partition, a Markov chain (MC), a multi-layer perceptron artificial neural network (MLP-ANN), and cellular automata (CA). This study employed multivariate land use data for the period 2000–2015 to conduct spatial clustering for the Ganjingzi District and to simulate landscape status evolution via a divisional composite cellular automaton model. During the period of 2000–2015, construction land and forest land areas in Ganjingzi District increased by 19.43% and 15.19%, respectively, whereas farmland, garden lands, and other land areas decreased by 43.42%, 52.14%, and 75.97%, respectively. Land use conversion potentials in different sub-regions show different characteristics in space. The overall land-change prediction accuracy for the subarea-composite model is 3% higher than that of the non-partitioned model, and misses are reduced by 3.1%. Therefore, by integrating geospatial zoning and the MLP-ANN hybrid method, the land type conversion rules of different zonings can be obtained, allowing for more effective simulations of future urban land use change. The hybrid cellular automata model developed here will provide a reference for urban planning and policy formulation.  相似文献   

An improved building detection approach using L-band POLSAR two-dimensional time-frequency decomposition over oriented built-up areas     

Lei Deng  Ying He  Zhi-hui Mao  Jie Yu 《地理信息系统科学与遥感》2019,56(1):1-21

The objective of this study is to efficiently extract detailed information about various man-made targets in oriented built-up areas using polarimetric synthetic aperture radar (POLSAR) images. This paper develops an improved approach for building detection by utilizing Two-Dimensional Time-Frequency (2-D TF) decomposition. This method performs outstandingly in distinguishing between man-made and natural targets based on the isotropic behaviors, frequency-sensitive responses, and scattering mechanisms of objects. The proposed method can preserve the spatial resolution and exploit the advantages of TF decomposition; specifically, the exact outlines of buildings can be effectively located, and more types of features (e.g., flat roofs, roads, and walls that are oblique to the radar illumination) can be distinguished from forests in complex built-up areas by 2-D TF decomposition. The coarser-resolution subaperture images that are produced in the azimuth direction, which correspond to different looking angles, are beneficial for detecting man-made structures with main scattering centers oriented at oblique angles with respect to the radar illumination. In the range direction, the obtained subaperture images, which correspond to various observation frequencies, can be helpful in distinguishing flat roofs and roads from forests. This method was successfully implemented to analyze both NASA/JPL L-band AIRSAR and L-band EMISAR data sets. The building detection results of the proposed method exhibit a significant improvement over those of other methods and reach an overall accuracy over 80%, with approximately 20% higher than the accuracies of K-means clustering and the entropy/alpha-Wishart classifier and approximately 10% higher than the accuracy of the support vector machine method. Moreover, building details can be precisely detected, obliquely oriented buildings can be identified, and the distinction between buildings and forests is significantly improved, as both visually and statistically indicated. This method is highly adaptable and has substantial application value.  相似文献   

中国区域MuSyQ叶面积指数产品验证与分析     

马培培  李静  柳钦火  何彬彬  赵静 《遥感学报》2019,23(6):1232-1252

对多源遥感数据协同生产的2010年—2015年中国区域1 km空间分辨率5天合成的MuSyQ（Multi-source data Synergized Quantitative remote sensing production system）叶面积指数LAI产品进行验证。参考现有的LAI产品（MODIS c5,GLASS LAI）和中国生态系统研究网络部分农田和森林站点可用的LAI地面测量数据,从时空连续性、时空一致性、精度和准确性等方面对中国区域的MuSyQ LAI产品进行定性和定量分析与评价。结果表明：（1） MuSyQ LAI产品在保证精度优于MODIS产品的情况下,时间分辨率和时空连续性均有提高。MuSyQ LAI与其他LAI产品（MODIS c5,GLASS LAI）在整体上有很好的一致性（RMSE=1.0,RMSE=0.81）,但对常绿阔叶林高值处的描述不稳定;（2） 与LAI地面测量数据相比,MuSyQ LAI产品与地面参考图对比结果较好（最高相关性（R²=0.54）和较低总体误差（RMSE=0.96））,其在阔叶作物生长季高值处有些许低估且在某些阔叶林站点有些高估。整体上,MuSyQ LAI产品呈现出较高的精度,可靠的空间分布和连续稳定的时间分布,且对森林LAI的描述具有更可靠的动态范围。  相似文献   

广角水体体散射函数测量技术及其应用研究进展     

徐聪辉  李彩 《遥感学报》2019,23(6):1078-1090

水体体散射函数是描述水体中光在各方向散射特性的一个重要的固有光学参数,对水色遥感、水环境监测与保护、海气交互过程研究、水下军事目标跟踪等领域具有十分重要的意义。水体体散射函数测量尤其是覆盖0°—180°范围的广角体散射函数测量技术起步较晚,直接测量难度较大,一直以来都是一个棘手的科学难题。本文梳理了国内外广角水体体散射函数测量技术的发展历程,对于广角体散射函数测量技术,从原理上大致可以分为单一探测器转动式、多个固定探测器阵列式以及面阵CCD成像式等3大类,对不同测量原理下的测量技术进行详细分析,并对广角水体体散射函数测量技术在海洋生物光学、气泡跟踪、水色遥感等方面的相关应用进展进行总结和归纳,并对未来广角水体体散射函数的发展趋势和应用前景进行展望。  相似文献   

Estimation of crowd density from UAVs images based on corner detection procedures and clustering analysis     

Ali Almagbile 《地球空间信息科学学报》2019,22(1):23-34

With rapid developments in platforms and sensors technology in terms of digital cameras and video recordings, crowd monitoring has taken a considerable attentions in many disciplines such as psychology, sociology, engineering, and computer vision. This is due to the fact that, monitoring of the crowd is necessary to enhance safety and controllable movements to minimize the risk particularly in highly crowded incidents (e.g. sports). One of the platforms that have been extensively employed in crowd monitoring is unmanned aerial vehicles (UAVs), because UAVs have the capability to acquiring fast, low costs, high-resolution and real-time images over crowd areas. In addition, geo-referenced images can also be provided through integration of on-board positioning sensors (e.g. GPS/IMU) with vision sensors (digital cameras and laser scanner). In this paper, a new testing procedure based on feature from accelerated segment test (FAST) algorithms is introduced to detect the crowd features from UAV images taken from different camera orientations and positions. The proposed test started with converting a circle of 16 pixels surrounding the center pixel into a vector and sorting it in ascending/descending order. A single pixel which takes the ranking number 9 (for FAST-9) or 12 (for FAST-12) was then compared with the center pixel. Accuracy assessment in terms of completeness and correctness was used to assess the performance of the new testing procedure before and after filtering the crowd features. The results show that the proposed algorithms are able to extract crowd features from different UAV images. Overall, the values of Completeness range from 55 to 70 % whereas the range of correctness values was 91 to 94 %.  相似文献   

灰关联GM(1,N)模型在建筑物沉降分析中的应用     

成枢  周龙飞  郭祥琳 《测绘与空间地理信息》2019,42(5):10-13

针对建筑物沉降变形中各监测点相互关联、相互影响的情形,可将灰色系统理论中的GM(1,N)模型引入到建筑物沉降分析中。本文利用灰度关联方法确定相关因子的关联度,建立GM(1,N)模型,并与回归分析、GM(1,1)模型比较。通过工程实例,得出灰关联GM(1,N)模型预测精度明显高于另外两种模型,验证了该模型在进行建筑物沉降分析预测中应用的可行性。  相似文献   

Building a model-based personalised recommendation approach for tourist attractions from geotagged social media data     

Xiaoyu Sun  Xia Peng  Yiran Chen  Yu Liu 《International Journal of Digital Earth》2019,12(6):661-678

When travelling, people are accustomed to taking and uploading photos on social media websites, which has led to the accumulation of huge numbers of geotagged photos. Combined with multisource information (e.g. weather, transportation, or textual information), these geotagged photos could help us in constructing user preference profiles at a high level of detail. Therefore, using these geotagged photos, we built a personalised recommendation system to provide attraction recommendations that match a user's preferences. Specifically, we retrieved a geotagged photo collection from the public API for Flickr (Flickr.com) and fetched a large amount of other contextual information to rebuild a user's travel history. We then created a model-based recommendation method with a two-stage architecture that consists of candidate generation (the matching process) and candidate ranking. In the matching process, we used a support vector machine model that was modified for multiclass classification to generate the candidate list. In addition, we used a gradient boosting regression tree to score each candidate and rerank the list. Finally, we evaluated our recommendation results with respect to accuracy and ranking ability. Compared with widely used memory-based methods, our proposed method performs significantly better in the cold-start situation and when mining ‘long-tail’ data.  相似文献   

Impact of different sampling rates on precise point positioning performance using online processing service     

Serdar Erol  Reha Metin Alkan  ?.Murat Ozulu  Veli Il?i 《地球空间信息科学学报》2021,24(2):302-312

In this study, the effect of different sampling rates (i.e. observation recording interval) on the Precise Point Positioning (PPP) solutions in terms of accurac...  相似文献   

不同草地类型净初级生产力(NPP)模拟及其敏感性分析     

张美玲  陈全功  蒋文兰 《干旱区地理》2021,44(2):369-378

气候变化问题作为人类社会可持续发展面临的重大挑战,受到国际社会越来越强烈的关注.全球气候变化深刻影响着草地生态系统,定量评估区域和不同类型草地生态系统的生产力,研究其对气候变化的敏感性可以为草地生态系统适应未来气候变化提供基础数据和理论依据.草原综合顺序分类系统(CSCS)将天然草原分为42类(其中中国包含41类),并...  相似文献