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arXiv 2018年

作者： Li, Tongwen Shen, Huanfeng Yuan, Qiangqiang Zhang, Liangpei School of Resource and Environmental Sciences Wuhan University Wuhan430079 China Collaborative Innovation Center of Geospatial Technology Wuhan430079 China Key Laboratory of Geographic Information System Ministry of Education Wuhan University Wuhan430079 China School of Geodesy and Geomatics Wuhan University Wuhan430079 China State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing Wuhan University Wuhan430079 China

Satellite-derived aerosol optical depth (AOD) has been increasingly employed for the estimation of ground-level PM2.5, which is often achieved by modeling the relationship between AOD and PM2.5. To evaluate the accuracy of PM2.5 estimation, the cross-validation (CV) technique has been widely used. There have been several CV-based validation approaches applied for the AOD-PM2.5 models. However, the applicable conditions of these validation approaches still remain unclear. Additionally, is there space to develop better validation approaches for the AOD-PM2.5 models? The contributions of this study can be summarized as two aspects. Firstly, we comprehensively analyze and assess the existing validation approaches, and give the suggestions for applicable conditions of them. Then, the existing validation approaches do not take the distance to monitoring station into consideration. A new validation approach considering the distance to monitoring station is proposed in this study. Among the existing validation approaches, the sample-based CV is used to reflect the overall prediction ability;the site-based CV and the region-based CV have the potentials to evaluate spatial prediction performance;the time-based CV and the historical validation are capable of evaluating temporal prediction accuracy. In addition, the validation results indicate that the proposed validation approach has shown great potentials to better evaluate the accuracy of PM2.5 estimation. This study provides application implications and new perspectives for the validation of AOD-PM2.5 models. Copyright © 2018, The Authors. All rights reserved.

关键词： Forecasting

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Geographically and temporally weighted neural networks for satellite-based mapping of ground-level PM2.5

arXiv

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arXiv 2018年

The integration of satellite-derived aerosol optical depth (AOD) and station-measured PM2.5 provides a promising approach for obtaining spatial PM2.5 data. Several spatiotemporal models, which considered spatial and temporal heterogeneities of AOD-PM2.5 relationship, have been widely adopted for PM2.5 estimation. However, they generally described the complex AODPM2.5 relationship based on a linear hypothesis. Previous machine learning models yielded great superiorities for fitting the nonlinear AOD-PM2.5 relationship, but seldom allowed for its spatiotemporal variations. To simultaneously consider the nonlinearity and spatiotemporal heterogeneities of AOD-PM2.5 relationship, geographically and temporally weighted neural networks (GTWNNs) were developed for satellite-based estimation of ground-level PM2.5 in this study. Using satellite AOD products, NDVI data, and meteorological factors over China as input, GTWNNs were set up with station PM2.5 measurements. Then the spatial PM2.5 data of those locations with no ground stations could be obtained. The proposed GTWNNs have achieved a better performance compared with previous spatiotemporal models, i.e., daily geographically weighted regression and geographically and temporally weighted regression. The sample-based and site-based cross-validation R2 values of GTWNNs are 0.80 and 0.79, respectively. On this basis, the spatial PM2.5 data with a resolution of 0.1 degree were generated in China. This study implemented the combination of geographical law and neural networks, and improved the accuracy of satellite-based PM2.5 estimation. Copyright © 2018, The Authors. All rights reserved.

关键词： Neural networks

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Does quality control matter? A revisit of surface urban heat island intensity estimated by satellite-derived land surface temperature products

Does quality control matter? A revisit of surface urban heat...

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ISPRS geospatial Week 2017

作者： Lai, Jiameng Zhan, Wenfeng Huang, Fan Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology International Institute for Earth System Science Nanjing University Nanjing Jiangsu210046 China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application Nanjing210023 China

Temporally regular and spatially continuous monitoring of surface urban heat island (SUHI) has been extremely difficult until the advent of spaceborne land surface temperature (LST) products. The higher errors of these LST products compared with in-situ measurements, nevertheless, have resulted in a comparatively inaccuracy and may distort the interpretation of SUHI. Although reports have shown that LST quality matters to the SUHI interpretation, a systematic investigation on how the SUHI indicators are responsive to the LST quality across cities within dissimilar bioclimates remains rare. With regard to this issue, our study chose eighty-six major cities across the mainland China and analyzed the SUHI intensity (SUHII) discrepancies (referred to as ΔSUHII) between using and not using quality control (QC) flags from Moderate Resolution Imaging Spectroradiometer data. Our major findings include: (1) the SUHII can be significantly impacted by the MODIS QC flags, and the associated seasonal ΔSUHIIs generally account for 25.5% (29.6%) of the total intensity in the day (night). (2) The ΔSUHIIs differ season-by-season and significant discrepancies also appear among northern and southern cities, with northern ones often possessing a higher annual mean ΔSUHII. (3) The internal ΔSUHIIs within an individual city are also heterogeneous, with the variations exceeding 5.0 K (3.0 K) in northern (southern) cities. (4) The ΔSUHII is significantly negatively related to the SUHII and cloud cover percentage mostly in transitional seasons. Our findings highlight that one needs to be very careful when using the LST-product-based SUHII to interpret the SUHI.

关键词： Quality control

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Enhanced modeling of remotely sensed Annual Land surface temperature cycle

Enhanced modeling of remotely sensed Annual Land surface tem...

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ISPRS geospatial Week 2017

作者： Zou, Zhaoxu Zhan, Wenfeng Jiang, Lu Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology International Institute for Earth System Science Nanjing University Nanjing Jiangsu210046 China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application Nanjing210023 China

Satellite thermal remote sensing provides access to acquire large-scale Land surface temperature (LST) data, but also generates missing and abnormal values resulting from non-clear-sky conditions. Given this limitation, Annual Temperature Cycle (ATC) model was employed to reconstruct the continuous daily LST data over a year. The original model ATCO used harmonic functions, but the dramatic changes of the real LST caused by the weather changes remained unclear due to the smooth sine curve. Using Aqua/MODIS LST products, NDVI and meteorological data, we proposed enhanced model ATCE based on ATCO to describe the fluctuation and compared their performances for the Yangtze River Delta region of China. The results demonstrated that, the overall root mean square errors (RMSEs) of the ATCE was lower than ATCO, and the improved accuracy of daytime was better than that of night, with the errors decreased by 0.64 K and 0.36 K, respectively. The improvements of accuracies varied with different land cover types: the forest, grassland and built-up areas improved larger than water. And the spatial heterogeneity was observed for performance of ATC model: the RMSEs of built-up area, forest and grassland were around 3.0 K in the daytime, while the water attained 2.27 K;at night, the accuracies of all types significantly increased to similar RMSEs level about 2 K. By comparing the differences between LSTs simulated by two models in different seasons, it was found that the differences were smaller in the spring and autumn, while larger in the summer and winter. © Authors 2017. CC BY 4.0 License.

关键词： Atmospheric temperature

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Two methods for remote estimation of complete urban surface temperature

Two methods for remote estimation of complete urban surface ...

引用

ISPRS geospatial Week 2017

作者： Jiang, Lu Zhan, Wenfeng Zou, Zhaoxu Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology International Institute for Earth System Science Nanjing University Nanjing Jiangsu210046 China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application Nanjing210023 China

Complete urban surface temperature (TC) is a key parameter for evaluating the energy exchange between the urban surface and atmosphere. At the present stage, the estimation of TC still needs detailed 3D structure information of the urban surface, however, it is often difficult to obtain the geometric structure and composition of the corresponding temperature of urban surface, so that there is still lack of concise and efficient method for estimating the TC by remote sensing. Based on the four typical urban surface scale models, combined with the Envi-met model, thermal radiant directionality forward modeling and kernel model, we analyzed a complete day and night cycle hourly component temperature and radiation temperature in each direction of two seasons of summer and winter, and calculated hemispherical integral temperature and TC. The conclusion is obtained by examining the relationship of directional radiation temperature, hemispherical integral temperature and TC: (1) There is an optimal angle of radiation temperature approaching the TC in a single observation direction when viewing zenith angle is 45 ∼ 60 °, the viewing azimuth near the vertical surface of the sun main plane, the average absolute difference is about 1.1 K in the daytime. (2) There are several (3∼5 times) directional temperatures of different view angle, under the situation of using the thermal radiation directionality kernel model can more accurately calculate the hemispherical integral temperature close to TC, the mean absolute error is about 1.0 K in the daytime. This study proposed simple and effective strategies for estimating TC by remote sensing, which are expected to improve the quantitative level of remote sensing of urban thermal environment.

关键词： Surface temperature

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Residents'environmental conservation behaviour in the mountain tourism destinations in China:Case studies of Jiuzhaigou and Mount Qingcheng

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Journal of Mountain Science 2017年第12期14卷 2555-2567页

作者： zhang yu-ling zhang jie zhang hong-ou zhang ruo-yang wang yang guo yong-rui wei zong-cai guangzhou institute of geography Guangzhou 510070China guangdong open laboratory of geospatial information technology and application Guangzhou 510070China school of geographic and oceanographic science nanjing universityNanjing 210046China shenzhen tourism college jinan universityShenzhen 518053China school of history culture and tourism jiangsu normal universityJiangsu Normal UniversityXuzhou 221116China school of architecture state key laboratory of subtropical building sciencesouth china university of technologyGuangzhou 510641China

This study aimed at gaining an understanding of the formation of residents' Environmental Conservation Behaviour(ECB) to promote sustainable tourism development in Chinese mountain areas. In particular, a theoretical framework was constructed by merging residents' mountain attachment and their environmental values,and awareness of environmental consequences based on the Cognition Behaviour Theory. This research sampled 642 residents with convenience sampling method in Jiuzhaigou and Mount Qingcheng, and structural equation modelling analysis was conducted to identify the relationships among the above variables. Results verified that mountain attachment affected people's awareness of environmental consequences, which then affected their *** values and mountain attachment directly and positively influenced ECB. Moreover,awareness of environmental consequences played the most prominent role in predicting ECB among all the predictors in this study. In all, this study derived several significant implications which can not only contribute to environmental management policies in tourism field but also help to improve the levels of the antecedents of residents' ECB and promote sustainable tourism development in Chinese mountain areas.

关键词： Sustainable tourism development Mountain attachment Environmental Conservation Behaviour Environmental values Cognitive Behaviour Theory

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Randomized consensus based distributed kalman filtering over wireless sensor networks

arXiv

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arXiv 2018年

作者： Qin, Jiahu Wang, Jie Shi, Ling Kang, Yu Department of Automation University of Science and Technology of China Hefei230027 China Department of Electronic and Computer Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong Department of Automation State Key Laboratory of Fire Science Institute of Advanced Technology University of Science and Technology of China Hefei230027 China Key Laboratory of Technology in Geo-Spatial Information Processing and Application System Chinese Academy of Sciences Beijing100190 China

This paper is concerned with developing a novel distributed Kalman filtering algorithm over wireless sensor networks based on randomized consensus strategy. Compared with centralized algorithm, distributed filtering techniques require less computation per sensor and lead to more robust estimation since they simply use the information from the neighboring nodes in the network. However, poor local sensor estimation caused by limited observability and network topology changes which interfere the global consensus are challenging issues. Motivated by this observation, we propose a novel randomized gossip based distributed Kalman filtering algorithm. information exchange and computation in the proposed algorithm can be carried out in an arbitrarily connected network of nodes. In addition, the computational burden can be distributed for a sensor which communicates with a stochastically selected neighbor at each clock step under schemes of gossip algorithm. In this case, the error covariance matrix changes stochastically at every clock step, thus the convergence is considered in a probabilistic sense. We provide the mean square convergence analysis of the proposed algorithm. Under a sufficient condition, we show that the proposed algorithm is quite appealing as it achieves better mean square error performance theoretically than the noncooperative decentralized Kalman filtering algorithm. Besides, considering the limited computation, communication and energy resources in the wireless sensor networks, we propose an optimization problem which minimizes the average expected state estimation error based on the proposed algorithm. To solve the proposed problem efficiently, we transform it into a convex optimization problem. And a sub-optimal solution is attained. Examples and simulations are provided to illustrate the theoretical results. Copyright © 2018, The Authors. All rights reserved.

关键词： Kalman filters

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An interactive system for low-poly illustration generation from images using adaptive thinning

An interactive system for low-poly illustration generation f...

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IEEE International Conference on Multimedia and Expo (ICME)

作者： Yiting Ma Xuejin Chen Yu Bai University of Science and Technology of China CAS Key Laboratory of Technology in Geo-spatial Information Processing and Application System

ISBN: (纸本)9781509060689

Low-poly style illustrations, which have 3D abstract appearance, have become a popular stylish recently. Most previous methods require special knowledges in 3D modeling and need tedious interactions. We present an interactive system for non-expert users to easily manipulate the low-poly style illustration. Our system consists of two parts: vertex sampling and mesh rendering. In the vertex sampling stage, we extract a set of candidate points from the image and rank them according to their importance of structure preserving using adaptive thinning. Based on the pre-ranked point list, the user can select an arbitrary number of vertices for the triangle mesh construction. In the mesh rendering stage, we optimize triangle colors to create stereo-looking low-polys. We also provide three tools for exible modication of vertex numbers, color contrast, and local region emphasis. The experiment results demonstrate that our system outperforms state-of-the-art method via simple user interactions.

关键词： Image color analysis Rendering (computer graphics) Tools Approximation error Interactive systems Three-dimensional displays Image edge detection

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Distance Measurement system Based on Binocular Stereo Vision

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IOP Conference Series: Earth and Environmental Science 2019年第5期252卷

作者： Xiyan Sun Yingzhou Jiang Yuanfa Ji Wentao Fu Suqing Yan Qidong Chen Baoguo Yu Xingli Gan Guangxi Key Laboratory of Precision Navigation Technology and Application Guilin University of Electronic Technology Guilin 541004 China National & Local Joint Engineering Research Center of Satellite Navigation and Location Service Guilin 541004 China Guangxi Experiment Center of Information Science Guilin University of Electronic Technology Guilin 541004 China Key laboratory of radio wave environment and modeling technology Qingdao 266000 China State key laboratory of satellite navigation system and equipment technology Shijiazhuang 050000 China

Binocular stereo vision uses two cameras of the same specification instead of human eyes for measurement and judgment. The basic principle of binocular vision ranging is to simultaneously capture the image of the measured object by using two left and right cameras. The objectmeasuredisdifferent, andthe positions under the different camera screensaredifferent, this difference in position is called disparity. The three-dimensional information of the object is obtained according to the principle of disparity. The binocular stereo vision ranging system, which combines the advantages of high efficiency and high precision, is ideal for non-contact detection and quality control. This paper proposes a method combining MATLAB calibration and OpenCV matching to achieve binocular stereo vision. Using the MATLAB calibration tool to perform stereo calibration of the camera, combined with OpenCV for stereo rectification and stereo matching, the disparity value is obtained, and the distance from the target to the camera is calculated by disparity. Simulations show that this method can satisfy the distance measurement.

关键词：

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Dynamic data packing towards the optimization of QoC and QoS in networked control systems

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Science China(Technological Sciences) 2016年第1期59卷 72-80页

作者： KANG Yu ZHAO YunBo Department of Automation and State Key Laboratory of Fire Science University of Science and Technology of China Key Laboratory of Technology in Geo-Spatial Information Processing and Application System Chinese Academy of Sciences Department of Automation Zhejiang University of Technology

A class of networked control systems is investigated whose communication network is shared with other applications. The design objective for such a system setting is not only the optimization of the control performance but also the efficient utilization of the communication resources. We observe that at a large time scale the data packet delay in the communication network is roughly varying piecewise constant, which is typically true for data networks like the Internet. Based on this observation, a dynamic data packing scheme is proposed within the recently developed packet-based control framework for networked control systems. As expected this proposed approach achieves a fine balance between the control performance and the communication utilization: the similar control performance can be obtained at dramatically reduced cost of the communication resources. Simulations illustrate the effectiveness of the proposed approach.

关键词： networked control systems packet delay variation dynamic data packing quality of control quality of service

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