To balance the contour accuracy and completeness of single threshold Alpha Shapes in extracting point cloud building contours, we present a dual-threshold Alpha Shapes algorithm using a simple ring design concept contour search algorithm to obtain both a good integrity and a relatively high geometric precision of the building’s contour. Furthermore, the initial contour is simplified based on least squares algorithm. In the presence of noise, the simplified contour lines of the present algorithm are closer to the actual contours compared with the classic Douglas Peucker algorithm.
In order to reduce the effect of inter-annual variations on cloud parameter, we computed the cloud parameter drought index with Inner Mongolia Autonomous Region as a case study. According to ground observation data, we selected appropriate characteristic value to calculate the background field data, and then modified the cloud parameter drought index. Results revealed that modified through background field data, the risk level of desert in middle and west Inner Mongolia and farmland in southeast Inner Mongolia reduced in 2006 and 2007, and the area of high risk level decreased apparently. In 2008, the high risk level in the north part of west Inner Mongolia and the southeast Inner Mongolia reduced as well, so did the high risk area. According to the monitoring results in every February from 2009-2011, we can conclude that the spatial distribution of monitoring results obtained by the present method are of good continuity, and the risk levels are closer to the real situation.
Active contour is an important method to segment images. Its segmentation strategy is usually edge-based or region-based and based on the contour energy minimization. But the classical active contour is difficult to deal with the region which has weak edges or is in the complicated background. In this paper, we implement an improved statistical region-based active contour and propose a strategy to extract region of interest by polygon. Within the family of exponential probability density function, statistical region-based active contour can run by fast algorithm. We give details of the realization of the algorithm and simplify the contour by the minimum description length. Experiment results illustrate the efficiency of our proposed method in contour extraction.
To analyze the spatial pattern of land-use and characteristics of land resources in Danjiangkou water-level-fluctuating zone, land-use status quo is monitored through remote sensing based on 0.5 m Digital Orthphoto Map in the reservoir area acquired through unmanned aerial vehicle by 2013 before impoundment of the reservoir area. Moreover, the characteristics of land-use status are studied using spatial analysis and geostatistical methods in association with administrative map, slope map and 150 m, 160 m, 163.5 m, 170m water flooding lines extracted from 1∶50 000 Digital Elevation Model. Results show that the areas of water-level-fluctuating zone are 227.1 km2 and 194.3 km2 at elevation 150-160 m and 160-170 m, respectively. Water-level-fluctuating zones are mainly distributed in Xichuan, Danjiangkou and Yunxian County. Arable land is the main land form in the fluctuating zone and is mainly distributed in Xichuan. The monitoring results provide a data basis for the management of Danjiangkou water-level-fluctuating zone.
In the aim of providing basic data and decision-making basis for soil and water conservation work,we carried out dynamic monitoring on soil and water loss and ecological environment under the support of RS, GIS and GPS technologies. With Ruxi River in Three Gorges Reservoir region as study area, we obtained the pattern, intensity and distribution of soil erosion through spatial overlay based on information of land-use types, vegetation coverage and slope gradient.According to Classification standard of soil erosion, we analyzed the dynamic changes of soil and water loss in 2014 and 2015, and adopted transfer matrix to analyze the area and types of land-use changes. Results suggest that from 2014 to 2015,although the land-use patterns of Ruxi River have experienced structural adjustment, the distribution of soil and water loss were generally stable. The area of microsoil erosion was slightly increased, the area of mild and intense soil erosion kept balance,the area of moderate soil erosion was slightly reduced, and the extremely or severe conditions have been alleviated.
Image segmentation by spectral clustering is a clustering method based on points. It is characterized by the use of similarity measure matrixes. We usually need to calculate the similarity matrixes between every two cells, which consumes huge computation task and a lot of time when processing large images. To solve this problem, we propose an improved method. First, we use mean shift algorithm for polarimetric SAR image, and then select center pixel to construct similarity measure matrix. At last, we use the normalized segmentation rule for image segmentation. Computation experiment proves that the algorithm could improve the efficiency with high accuracy and satisfactory result, hence is of practical significance.
LiDAR point cloud is a 3D point set composed of massive discrete laser dots which exist in both plane and vertical directions. Because of lacking space topological relations among the discrete dots of LiDAR point cloud, it is important to establish an appropriate data structure for LiDAR point cloud as the foundation of LiDAR processing. According to the structural characteristics of LiDAR point cloud data, a two-level data structure with “non-null” regular cube grid and K-D tree is established for the organization and management LiDAR point cloud using red-black tree and K-D tree to build. The structure could reduce the structural redundancy and improve indexing efficiency.
In this paper, an automatic change detection method based on fusion of spectral and geometrical features for multi-temporal high-resolution remote sensing image is proposed. Firstly, as to the characteristic of complicated classes in urban area, spectral and geometrical difference images are developed using multi-temporal images. Secondly, with difference image as input, the membership images of changed and unchanged classes are acquired using
fuzzy classification method. Thirdly, a fusion model based on fuzzy logic theory is used to combine all kinds of membership images in order to reduce the fuzziness and to distinguish the changed and unchanged classes of special areas efficiently. Finally, change detection result is obtained using threshold segmentation algorithm and accuracy evaluation is given. Multi-temporal high-resolution images of urban area are taken as experimental data, and the experimental results prove that the change detection result fusing spectral and geometrical features has higher detection precision and lower undetected ratio compared with those from spectral or geometrical difference image methods.
The expansion of construction land use needs to be predicted in consideration of the influence of spatial pattern factors. In this research, we take the main urban area of Chongqing city as study area to predict the spatial distributions of construction land use demand and newly built construction land in 2020 using the method of average growth rate of construction land in association with land use superiority evaluation of three spatial factors (elevation, slope, and original land-use type)by GIS technological means. Results indicate that1) between 2010 and 2016, the area of urban construction land in urban Chongqing has increased from 749.14 km2 to 905.06 km2, with an average annual growth rate of 3.35%; 2) newly built area were mainly transformed from cultivated land(accounting for 53.25%) and forest land(37.89%), and more likely located in the area of slope gradient smaller than 12°and elevation below 400m, especially in the range of 0-3° slope (24.44%)and 200-300 m elevation(47.60%); 3) up to 2020, the area of urban construction land will be increased by 115.31 km2, mainly transformed from cultivated land (56.24%) and distributed in the range of 200-300m elevation (47.45%) and 0-12°slope (58.39%), mainly located in Shapingba district, Jiulongpo district and Yubei district.
Distributed hydrological model is currently the hotspot of watershed model research. In this research, the data storage, physical realization and message communication of distributed hydrological model in Web-based GISframework are discussed through integrating distributed hydrological model with Web-based GIS technology. A complete scheme of integrating distributed hydrological model with Web-based GIS is designed, based on which the network computing service of CREST (Coupled Routing and Excess Storage) model is accomplished. The results suggest that the integration of distributed hydrological model and Web-based GIS technology expands the scope of the application of distributed hydrological model.
In this paper, water pollution diffusion is simulated and analyzed by information and visualization technology during water pollution emergency events. A simulation and decision support system for water pollution based on WebGIS is proposed to represent and manage data in two-dimensional network environment. Data is the key part of the system,including data acquisition, transmission, simulation analysis and application. In this system, the visualization and interactive application of two-dimensional diffusion models of water pollution and simulation result are researched in emphasis in the Internet environment. A section of the mainstream Yangtze River is taken as the experimental region to test the effectiveness. Experimental result proves that the system could effectively support the automatic monitoring and decision-making of water pollution emergency events.
Big data technology is an emerging information technology. In this paper, the design of big data resourcesframework for water conservancy industry is presented through analyzing the characteristics of big data complexity and uncertainty as well as the application demands of water conservancy industry. The architectural design of big data resources in water resources industry is put forward. Moreover, the information sharing mechanism of integrated information platform is researched, and cloud computing and cloud storage applications, as well as 3D intelligent collaborative design process are discussed. Finally, the prospect of big data technology applied in water conservancy industry is presented. Big data technology will bring about far-reaching influence on the development of water conservancy industry.
Quickly and efficiently obtaining river network information is of great significance for basin hydrological analysis. In this paper, the fundamental information of flow direction, flow accumulation raster, and river network is extracted using ArcGIS based on DEM(digital elevation model) data with spatial resolution of 30 meters. Liugu river watershed in Liaoning province is taken as a case study. Furthermore, the extraction results are compared with the real river stream with spatial resolution of 1∶4 000 000, and the main river stream network matches well. The area difference between the extraction and the actual basin is only 1.99%, indicating that the spatial information technology is available to the watershed characteristics extraction. The extraction data could provide data support for hydrologic simulation and digital basin construction.
The North Hubei Water Transfer Project is the biggest water resource project in Hubei Province. It has problems inclusive of big investment,limited construction period,long water conveyance line,complex engineering process,many construction units involved,and uneven personnel quality.In view of this,according to technical specifications for hydro-project construction management issued by the Ministry of water resources and several internal management documents issued by the Administration of the North Hubei Water Transfer Project such as Infrastructure construction management measures for the North Hubei Water Transfer Project, we designed and implemented the information system for the construction management of North Hubei Water Transfer Project with the combination of Microsoft C# and Microsoft SQL Server 2012 program languages. The system has already been used for trial in Danjiangkou-Xiangyang construction management branch, Zaoyang-Suizhou branch, and Guangshui-Dawu branch for three months. Results show that with the aid of the system, the complex hierarchical management of multi-type users is improved, the information reporting process is standardized, the efficiency of infrastructure statistics construction is enhanced, and the engineering construction process scenario is better displayed. The work flow is standardized, transparent, and can be traced, which suggests that the information level of the North Hubei Water Transfer Project is improved remarkably.
In this research we propose an improved approach of creating tile pyramid in real time for multi-scale images to resolve the problems of poor versatility of image data and low efficiency of data updating caused by traditional virtual globes to create tile pyramid beforehand. In the proposed model, clip and mosaic of images in logic sense are obtained, and then the tile pyramid project is published as data service, and tile data is created in real time by a parallel computing program based on multiprocessor. The model was trialed with Worldwind using the multi-source images of Guangdong and Hainan Provinces. Test results show that the present method is convenient in managing original image data and responding customers’ requests. Meanwhile, it remarkably improves the efficiency of updating image data.
Non-contact surface displacement measurement, as a nondestructive measurement technology, has been widely used in many engineering fields. For concrete’s stress and strain testing and river channel’s instantaneous flow field measurement, we developed non-contact surface displacement measurement systems based on digital speckle correlation method and particle image velocimetry. Some key issues in the developed systems are discussed and the corresponding treatments are given. The experimental result proves the effectiveness of the proposed method. Nevertheless, there are still some technical defectives to be furthered researched, including 3-D velocimetry of multi-perspective CCD camera, multi-purpose line tracing, and highly-precise fusion of measurement data of different scenes.
Site monitoring plays an important role in scientific research and engineering fields. Improving the information level and practical level by applying new technology in site monitoring is currently a research hotspot. In this research, UAV (unmanned aerial vehicle) panoramic technology is applied to site monitoring to build a 3D virtual reality environment, which is integrated with monitor sensors to form a 3D panoramic site-monitoring platform using computer networks. On this platform, the 3D real-time monitoring is implemented and the user experience of site monitoring system is enhanced, which demonstrates the potential of UAV panoramic technology in site monitoring.
In view of China’s current serious water loss and soil erosion, the Unmanned Aerial Vehicle (UAV) oblique photography technique was introduced as an auxiliary monitoring method in land use field sampling in the Three Gorges Reservoir area of Yangtze River Basin to carry out remote sensing dynamic monitoring of soil and water conservation. High resolution remote sensing images obtained by satellite ZY-3 and GF-1 were selected as the main data source in soil and water conservation dynamic monitoring. Practice showed that China’s domestic satellite image quality has improved significantly by obviously reflecting the characteristics of land use types such as rice paddy field,slope farmland, orchard,tea garden, and forest land. Satellite ZY-3 and GF-1 can be effectively applied to the remote sensing dynamic monitoring of soil and water conservation. Moreover, as an auxiliary monitoring method, UAV technology has great potential in soil and water conservation and other related fields.
According to the need of photogrammetry and the characteristics of multi-rotor UAV(unmanned aerial vehicle),a scheme of oblique image acquisition using single-lens camera is proposed through analyzing the principle of conventional multi-lens camera in terms of hardware selection,process optimization and software research, and its feasibility is verified through experiment. Furthermore, the key processes of the multi-rotor UAV using single-lens camera are presented, including route planning method and aerial quality control standard. Besides,a mobile ground station App oriented to the demand of oblique image acquisition is designed.Test results show that under given operation standards,the multi-rotor UAV with single-lens camera could well implement 3D ground modeling.
In order to alleviate the impact of greenhouse gas emission on climate change, the green hydropower assessment that centers on the harmonious development between clean hydropower and eco-environment has become a research hotspot. In accordance with the current situation of research on green hydropower in China and abroad, a complete, independent, representative, comparable and implementable indicator system is proposed in this paper, and the green hydropower evaluation indicators and their thresholds are explored by analyzing the environmental, economic and social impacts of the construction and operation of cascade hydropower projects in typical areas of the upper reaches of the Yangtze River from perspectives of flood control, ship transport, energy, eco-environment, ecological compensation for immigrants and cultural and landscape compensation. International green hydropower certification system and the present technical standards in China are taken as basis. Moreover, by choosing typical cases as the pilot ones, an evaluation system of ecological protection, economic benefits and social influence that covers the full life circle of the hydropower projects is established to guarantee an environmental-friendly construction of hydropower projects in China and to promote the sustainable development of clean hydropower energy in China.
According to the requirement of mountain flood prevention project,we conducted research on flood impact and inundation of urban area.Baokang county in Hubei Province was selected as a typical mountainous county for case study.Through field investigation and data collection,we designed flood calculation schemes,and built hydrodynamics model,flood routing model and flood inundation model.The calculation results reveal that the method has good theoretical basis,fast calculation speed and accurate calculation results.Moreover,two-dimensional model nesting and rational and reliable flood impact analysis are carried out in this paper.The research results can provide valuable reference for flood control decision-making departments.
According to the 1∶10 000 topographic map in 2000 and the Strahler river classification, the spatial-dimensional features of Dianchi Lake basin which belongs to plateau mountainous area and its differences with coastal plain river network were analyzed based on GIS platform from aspects of drainage pattern,river density, river system complexity and drainage connectivity. Moreover, the influences of water conservancy projects on the regional river structure and function were evaluated, and an evaluation index F based on connectivity connotation was proposed and applied to the basin. Results showed that 1) the river structure in Dianchi Lake basin conforms with Horton law, and the difference of drainage pattern in spatial dimension is not significant; 2) compared with those of coastal areas, the drainage density is low in the basin, and the drainage development degree is not high; 3) reservoir projects increase the rate of water surface and storage capacity in the basin, which can be reflected well by the Hurst index; 4) the evaluation index F could well reflect the role of projects in basin connectivity.
To achieve the well-off water conservancy in a well-off society before 2020, the well-off water conservancy planning is undergoing in Yunnan Province. In this research, an assessment index system consisting 26 indexes in aspects of flood control and drought relief,reasonable allocation of water resources, effective water utilization, water source protection and river health, water management and water development is proposed based on the method of analytic hierarchy process (AHP). The index weights are calculated by AHP method, and the index system is used to evaluate the status quo of water conservancy development in Yunnan province in 2011. Results reveal that the score of well-off water conservancy in Yunnan province at present is 71, and there is still some way to go; whereas the score of water management ability is only 40.8, which is the main restrictive factor, consistent with the actual condition of water development in Yunnan. The results could be used as the basis for the well-off water conservancy planning in Yunnan Province.
In this paper, the spatial and temporal distribution of extreme precipitation in different time scales(1 h, 6 h, 24 h) in Zhaotong, Yunnan Province were analyzed based on the data from 19 meteorological stations during 1969-2014. The Mann-Kendall trend test and wavelet transform were used to analyze the period and trend characters of three typical stations (Yudong, Xinhua, and Niujie). Then the Inversed Distance Weight method was used to interpolate the point data into the area. The results show that the trend of extreme precipitation from three typical stations is not obvious (p>0.05). The periods for these three typical stations are 30 a, 15 a and 5-7 a,respectively. The spatial distribution of the extreme precipitation differs greatly from north to south, which is larger in the North and smaller in the South.
