High-speed railway construction will produce a large amount of abandoned dregs, so it is necessary to build enough dreg deposition fields along the railway. The task of the department of soil and water conservation is to monitor the construction and usage of abandoned dreg fields according to the design in the whole process of railway construction. As long linear construction projects, many high-speed railways go through regions of complex terrain, which poses great difficulties to monitoring current status of abandoned dreg fields. With the advantages of low cost, flexible launch and landing, safety, under-cloud-flying, hyperspatial image resolution, Unmanned Aerial Vehicles (UAVs) are very suitable for obtaining remote sensing imagery along the railway. One segment of the high-speed railway from Chongqing to Wanzhou and its neighborhood was chosen as the study area to demonstrate key technologies and specific procedures of monitoring abandoned dreg fields using the UAV system. The UAV system and its components are introduced along with the flight trajectories, acquired UAV imagery, and attitude data. Image preprocessing and generation of DEM and DOM are described in detail followed by image-based measurement accuracy assessment and abandoned dreg field status investigation on the resulting DOM and DEM. Results prove the feasibility and effectiveness of applying the fixed wing UAV system to rapidly monitoring the construction and usage of abandoned dreg fields
Due to its unique geographical location and regional climate, the Yellow River and its tributaries are prone to ice jams almost every spring. Ice jams can cause levees to burst, leading to severe flooding, property damage, and human casualties. Hence, there is an urgent need to carry out observations of ice conditions and make risk assessments of ice jam occurrence. Field observation is the most reliable technique, but it is usually too expensive and time-consuming, which has led to the evaluation of applied remote sensing for data capture and analysis. Owing to the factors of timeliness, image resolution, human safety, and cost, satellite or manned aerial remote sensing cannot fully meet the requirements of ice condition observation. An unmanned aerial vehicle (UAV) remote sensing system is proposed for the collection of river ice imagery, providing the benefits of low cost, flexible launch and landing logistics, safety, and appropriate hyperspatial image resolution. One Inner Mongolian segment of the Yellow River was chosen as a test area to demonstrate key technologies and specific procedures of observation and assessment of ice conditions using the UAV system. The specific UAV remote sensing system and its components are introduced along with the procedures of UAV operation and imagery acquisition. Image preprocessing techniques and ice information extraction are described in detail followed by analysis and risk assessment of the ice conditions based on the resulting panoramic imagery. Results prove the feasibility and effectiveness of applying the fixed-wing UAV system to rapid observation and risk assessment of ice jam formation over the Yellow River under harsh weather conditions including low temperatures and strong winds.
The development and application of spatial database ultimately create the demand for spatial information security, and
access control is our primary concern. The access control requirements for spatial database contain two special aspects:
1) fine-grained; 2) meeting certain conditions, including spatial and non-spatial. In this paper, we propose a view-based
mechanism to implement access control functionalities. We firstly present the authorization model for spatial data. Then
we thoroughly discuss the definition of various views and their authorization, and explain the advantages and
disadvantages of this model. We also provide a reference framework for the view-based access control system, and the
components and control flow are explained. Finally, we use a case study to demonstrate the feasibility and effectiveness
of view-based authorization model for securing spatial database access.
The data-intensive and computation-intensive characteristics of the geo-processing require scalable, flexible, and distributed geo-computing platforms. We employ P2P and Grid technologies to construct a prototype of P2P-Grid GIS, which can integrate distributed spatial data and computing resources to accomplish complex and large-scale spatial processing tasks. The JXTA is a general P2P toolkit originally used in our system. It has many modules and functionalities unnecessary for the prototype, which prove to decrease the system performance. Therefore, we design our own P2P communication scheme called CoreP2P. In this paper, we firstly give a brief description of the architecture of P2P-Grid GIS. We also identify the group communication requirements in the P2P-Grid GIS, which include spatial data transfer and control message transmission. Then, we discuss the components of CoreP2P and their respective
functionalities in detail. Finally, we build the P2P-Grid GIS based on CoreP2P and compare the performance with JXTA-based system.
GridGIS is the application of grid computing technology on GIS field, which aims to realize the spatial information sharing and cooperative service. However, current grid technologies are generally difficult to use, so the development and deployment of Web portals that simplifies usage of grid resources has become popular. Grid-enabled portals can thus serve as simple, single points of entry or gateway to multiple computing resources, providing access to complex grid
tools and services. In this paper, we give an overview of GridGIS project and the key role of that GridGIS portal is playing in reaching its goals. Then, we describe the portal and Open Grid Computing Environment (OGCE) portal toolkit. Basing on OGCE and integrated Open Geospatial Consortium (OGC) Web service, we design the architecture of the GridGIS portal. In an open source development environment, we develop and deploy GridGIS portal, which includes
authentication module, Grid Port Information Repository (GPIR) portlet, Comprehensive File Management (CFM) portlet, Grid Resource Allocation and Management (GRAM) portlet and Map Viewer portlet.