Haidong Zhong

Monitoring urban expansion and land use/land cover changes of Shanghai metropolitan area during the transitional economy (1979–2009) in China

This study explored the spatio-temporal dynamics and evolution of land use/cover changes and urban expansion in Shanghai metropolitan area, China, during the transitional economy period (1979–2009) using multi-temporal satellite images and geographic information systems (GIS). A maximum likelihood supervised classification algorithm was employed to extract information from four landsat images, with the post-classification change detection technique and GIS-based spatial analysis methods used to detect land-use and land-cover (LULC) changes. The overall Kappa indices of land use/cover change maps ranged from 0.79 to 0.89. Results indicated that urbanization has accelerated at an unprecedented scale and rate during the study period, leading to a considerable reduction in the area of farmland and green land. Findings further revealed that water bodies and bare land increased, obviously due to large-scale coastal development after 2000. The direction of urban expansion was along a north-south axis from 1979 to 2000, but after 2000 this growth changed to spread from both the existing urban area and along transport routes in all directions. Urban expansion and subsequent LULC changes in Shanghai have largely been driven by policy reform, population growth, and economic development. Rapid urban expansion through clearing of vegetation has led to a wide range of eco-environmental degradation.

A solution for the data collection in the field survey based on Mobile and Wireless GIS

Traditional data collection methods for geological investigation, profile measurement, and other field survey in the research community of geosciences are generally based on the manual measuring and recording by the investigators. The most popular “instruments” used in the traditional survey are pencils as well as printed hard copy charts. The methods are obviously complicated and inefficient, at the same time the collected data are always inaccurate and not compatible with the digital process in computer. For these reasons, a solution for the data collection in the field survey based on Mobile and Wireless GIS is proposed in this study. Key technologies involved in the solution are reviewed at first. Then, a prototype of mobile GIS with basic GIS functions is designed and implemented based on independent development. Important technologies of implementation some basic GIS services for data collection in mobile environment introduced and many key challenges related, which are overcome in the process of the system development, are studied in detail.

Vulnerability assessment of combined impacts of sea level rise and coastal flooding for China's coastal region using remote sensing and GIS

Chinas coastal region is physically and socio-economically vulnerable to accelerated sea-level rise and associated coastal flooding because of its low topography, highly developed economy and highly-dense population. In this study, we present a scenario of sea level rise and storm surge flooding along the Chinas coastal region over the next century and apply them to a digital elevation model (DEM) which acquired by the shuttle radar topography mission (SRTM) to illustrate the extent and spatial distribution to which coastal areas are susceptible to permanent inundation and episodic flooding due to storm events. To perform flood scenario analysis and vulnerability assessment, a method for producing several sets of data was implemented by combining remote sensing processing, the use of grid-based socio-economic data, and subsequent analysis using Geographical Information Systems (GIS). This analysis shows that inundation and coastal flooding will mainly occur in the major delta without the protection of dike systems. However, due to the concentration of population and economic activities in Chinas coastal region, societal and economic consequences of continued sea-level rise would be substantial. Finally, some suggestions are presented for decision-makers, and other concerned stakeholders to develop appropriate public policies and mitigation measures.

An approach for integrating geospatial processing services into three-dimensional GIS

Three-dimensional (3D) GIS is gaining more and more acceptance among both scientists and the general public. Though powerful in data visualization, 3D GIS is comparatively weak in geospatial analysis. In order to enhance 3D GISs analysis capability, we present an approach for integrating geospatial processing services into 3D GIS. The architecture of our approach contains four layers which are the Presentation layer, the Application layer, the Service layer and the Data layer. Two different workflows are designed for this architecture to deal with geospatial tasks of different complexities. We also implement this approach in a 3D GIS project named Digital Chongming Island (DCI), Shanghai, China. By successfully integrating a variety of geospatial processing services into DCI, we have demonstrated that our approach is feasible and effective.

A method for representing thematic data in three-dimensional GIS

The effective representation of thematic data in 3D GIS can not only visualize tabular data intuitively in 3D environment, but also enable users to analyze thematic data directly on 3D GIS platform, thereby facilitating the decision making process. This paper proposes a method for representing thematic data in 3D GIS. Three steps are included in the method. In the first step, user is required to input some thematic representation parameters, all of which are then automatically converted into a XML fragment. In the second step, the API of the 3D GIS platform is employed to build graphic symbols according to the representation parameters and the thematic data. In the last step, we create legend and annotations to accurately interpret the meanings of the graphic symbols to user. This method has also been implemented as a module in a 3D GIS project named Digital Chongming Island, and the census data of Chongming Island are effectively represented in 3D environment.

Spatial indexing of global geographical data with HTM

Spatial indexing is one of the most important techniques in the field of spatial data management. Many kinds of techniques of spatial indexing have been successfully developed, and each of them has advantages towards special applications. As a type of spatial data structure, Hierarchical Triangular Mesh (HTM) has excellent features of global continuity, stability, hierarchy and uniformity, which has attracted much interest of researchers for many years. This paper investigates the method that using HTM as indexing for global geographical data (only point-like objects now). The HTM is defined by subdividing a unit sphere recursively and the basic elements in it are spherical triangles that are coded as integers called HTM codes in the computer system. At the global scale, all the regions on the sphere are spherical, which can be intersected with HTM elements obeying some equations. The spatial position of each input object can also be represented by a HTM code. HTM codes thus become the bridge between query regions and input objects. Our system is based on the combination of database management system (DBMS) and distributed file system. The major information of input files is extracted as metadata that are stored on tables of DBMS, while the original files are stored on the distributed file system (called HDFS) which has potential abilities to support parallel processing. Millions of point-like objects on the global were examined and the experiments indicated the system were acceptable.