Zhou Huang

Practical application of unmanned aerial vehicles for mountain hazards survey

Mountain disasters like landslides occur frequently in Southwest China. Hence, it is urgent to timely conduct geological survey in disastrous region and take necessary measures to treat identified hazards. Field survey is reliable but too expensive and time-consuming. Satellite or manned aerial remote sensing have the advantages of region-scale coverage and moderate timeliness, but restricted by the factors of mist, image resolution, human safety, and cost. Unmanned Aerial Vehicle (UAV) remote sensing is a very promising approach for rapid disaster investigation in regional scope, as giving consideration to both accuracy and spatial coverage. In this paper, we demonstrate our practice and experiences in applying UAVs in the survey of mountain hazards from the aspects of UAV customization and modification, UAV image pre-processing, and UAV imagery Interpretation.

Local acceleration in Distributed Geographic Information Processing with CUDA

DGIP (Distributed Geographic Information Processing) has become a new tendency of GIS (Geographic Information System) recently. DGIP focuses on how to organize and process a series of geographic resources in distributed computing environment and now existing research is mainly carried out from a global point of view. But it is noticeable that each computing node in distributed computing environment will carry a heavy load with growth of data quantity. So this paper concentrates on how to make each computing node fulfill the subtask more quickly to achieve efficient local acceleration. The paper designs a prototype for distributed remote sensing image processing and achieves local acceleration in each computing node with CUDA (Compute Unified Device Architecture). Firstly, the paper introduces the distributed procedure of the prototype and overviews the architecture and programming model of CUDA. Then the paper takes Mean Filter as an example to design and implement the parallel program with CUDA to accelerate the procedure of remote sensing image processing in each node. To evaluate the performance of the local acceleration, the paper carries out a group of comparative tests between the parallel implementation with CUDA and the conventional implementation. The results demonstrate that the local acceleration with CUDA runs more than 20 times faster than conventional process.

A global-view-oriented approach to directory management in distributed spatial database

Based on discussion on general methods of constructing global directory in DSMDS (Distributed Spatial Database Management System), a new approach based on relation model was brought forward. It specifies three main components of the global directory, including directory organization, directory update and extern interface. Then the authors implemented an actual global directory named SDirectoryService as well, key approaches and techniques in implementation were discussed in detail. Some experiments were designed and performed to check the efficiency, correctness and feasibility of the global directory, which reveal the directory works well on each aspect. By using the directory effective global query processing was achieved in DSMDS.

Toward an integrated framework for geosensor grid

Abstract Grid computing is deemed as a good solution to the digital earth infrastructure. Various geographically dispersed geospatial resources can be connected and merged into a ‘supercomputer’ by using the grid-computing technology. On the other side, geosensor networks offer a new perspective for collecting physical data dynamically and modeling a real-time virtual world. Integrating geosensor networks and grid computing in geosensor grid can be compared to equipping the geospatial information grid with ‘eyes’ and ‘ears.’ Thus, real-time information in the physical world can be processed, correlated, and modeled to enable complex and advanced geospatial analyses on geosensor grid with capability of high-performance computation. There are several issues and challenges that need to be overcome before geosensor grid comes true. In this paper, we propose an integrated framework, comprising the geosensor network layer, the grid layer and the application layer, to address these design issues. Key technologies of the geosensor grid framework are discussed. And, a geosensor grid testbed is set up to illustrate the proposed framework and improve our geosensor grid design.

Development of a Grid GIS Prototype for Geospatial Data Integration

Recently, there has been a fast proliferation of applications creating geospatial data distributed somewhere that has to be processed, queried and analyzed efficiently. Consequently, there is a need for effective data processing technologies that are able to support such distributed query and analysis operations. The emergence of grid computing offers a well solution to accomplish this goal. Development technologies to accomplish grid GIS were derived in this paper. After discussing the structure of grid GIS for geospatial data integration, one actual prototype system was designed and then implemented. Several implementation methods, including global directory construction and global parsing algorithm, were brought forward in this paper. Through the grid system, integration of distributed geospatial data was achieved.

Building the distributed geographic SQL workflow in the Grid environment

Over recent years, massive geospatial information has been produced at a prodigious rate, and is usually geographically distributed across the Internet. Grid computing, as a recent development in the landscape of distributed computing, is deemed as a good solution for distributed geospatial data management and manipulation. Thus, the Grid computing technology can be applied to integrate various distributed resources into a ‘super-computer’ that enables efficient distributed geospatial query processing. In order to realize this vision, an effective mechanism for building the distributed geospatial query workflow in the Grid environment needs to be elaborately designed. The workflow-building technology aims to automatically transform the global geospatial query into an equivalent distributed query process in the Grid. In response to this goal, detailed steps and algorithms for building the distributed geospatial query workflow in the Grid environment are discussed in this article. Moreover, we develop corresponding software tools that enable Grid-based geospatial queries to be run against multiple data resources. Experimental results demonstrate that the proposed methodology is feasible and correct.

An Effective NoSQL-Based Vector Map Tile Management Approach

Within a digital map service environment, the rapid growth of Spatial Big-Data is driving new requirements for effective mechanisms for massive online vector map tile processing. The emergence of Not Only SQL (NoSQL) databases has resulted in a new data storage and management model for scalable spatial data deployments and fast tracking. They better suit the scenario of high-volume, low-latency network map services than traditional standalone high-performance computer (HPC) or relational databases. In this paper, we propose a flexible storage framework that provides feasible methods for tiled map data parallel clipping and retrieval operations within a distributed NoSQL database environment. We illustrate the parallel vector tile generation and querying algorithms with the MapReduce programming model. Three different processing approaches, including local caching, distributed file storage, and the NoSQL-based method, are compared by analyzing the concurrent load and calculation time. An online geological vector tile map service prototype was developed to embed our processing framework in the China Geological Survey Information Grid. Experimental results show that our NoSQL-based parallel tile management framework can support applications that process huge volumes of vector tile data and improve performance of the tiled map service.

An approach for heterogeneous and loosely coupled geospatial data distributed computing

Most GIS (Geographic Information System) applications tend to have heterogeneous and autonomous geospatial information resources, and the availability of these local resources is unpredictable and dynamic under a distributed computing environment. In order to make use of these local resources together to solve larger geospatial information processing problems that are related to an overall situation, in this paper, with the support of peer-to-peer computing technologies, we propose a geospatial data distributed computing mechanism that involves loosely coupled geospatial resource directories and a term named as Equivalent Distributed Program of global geospatial queries to solve geospatial distributed computing problems under heterogeneous GIS environments. First, a geospatial query process schema for distributed computing as well as a method for equivalent transformation from a global geospatial query to distributed local queries at SQL (Structured Query Language) level to solve the coordinating problem among heterogeneous resources are presented. Second, peer-to-peer technologies are used to maintain a loosely coupled network environment that consists of autonomous geospatial information resources, thus to achieve decentralized and consistent synchronization among global geospatial resource directories, and to carry out distributed transaction management of local queries. Finally, based on the developed prototype system, example applications of simple and complex geospatial data distributed queries are presented to illustrate the procedure of global geospatial information processing.

Fundamental aspects of access control for geospatial data

Abstract In recent years, geographical information systems have been employed in a wide variety of application domains, and as a result many research efforts are being devoted to those upcoming problems. Geospatial data security, especially access control, has attracted increased research interests within the academic community. The tendency towards sharing and interoperability of geospatial data and applications makes it common to acquire and integrate geospatial data from multiple organisations to accomplish a complex task. Meanwhile, many organisations have the requirement for securing access to possessed sensitive or proprietary geospatial data. In this heterogeneous and distributed environment, consistent access control functionality is crucial to promote controlled accessibility. As an extension of general access control mechanisms in the IT domain, the mechanism for geospatial data access control has its own requirements and characteristics of granularity and geospatial logic. In this paper, we address several fundamental aspects concerning the design and implementation of an access control system for geospatial data, including the classification, requirements, authorisation models, storage structures and management approaches for authorisation rules, matching and decision-making algorithms between authorisation rules and access requests, and its policy enforcement mechanisms. This paper also presents a system framework for realising access control functionality for geospatial data, and explain access control procedures in detail.

Inferring spatial interaction patterns from sequential snapshots of spatial distributions

ABSTRACT Spatial interactions underlying consecutive sequential snapshots of spatial distributions, such as the migration flows underlying temporal population snapshots, can reflect the details of spatial evolution processes. In the era of big data, we have access to individual-level data, but the acquisition of high-quality spatial interaction data remains a challenging problem. Most research has been focused on distributions of movable objects or the modelling of spatial interaction patterns, with few attempts to identify hidden spatial interaction patterns from temporal transitions of spatial distributions. In this article, we introduced an approach to infer spatial interaction patterns from sequential snapshots of spatial population distributions by incorporating linear programming and the spatial constraints of human movement. Experiments using synthetic data were conducted using four simple scenarios to explore the characteristics of our method. The proposed method was used to extract interurban flows of migrants during the Chinese Spring Festival in 2016. Our research demonstrated the feasibility of using discrete multi-temporal snapshots of population distributions in space to infer spatial interaction patterns and offered a general analytical framework from snapshot data to spatial interaction patterns.