Gong Huili

Using RS and GIS to monitoring Beijing wetland resources evolution

In Beijing, Wetlands have been playing a crucial role in conserving municipal freshwater and retaining biodiversity. The classification system of Beijing wetland has been set up. The interpretation keys of six main wetland types in Beijing, including River, Reservoir, City Lake, Artificial Canal, Pound and Paddy Field, were built up using TM/ETM+ multi-spectral pseudo-color composition images as the data source. The modern information technology such as RS, GIS and GPS is combined with field investigation for further analysis to obtain the historical change information of wetland area, water quality and landscape pattern, The wetland soil and plant distribution maps in different large scale were sketched, and their attribute databases including hydrology, soil and plant were built up also. From which, its trend of evolution and some driving factors are analyzed successfully. This study indicates that not only have wetland areas been reduced by half, but also their ecological environments have been degraded because of rapid economic development and population increase. Suggestions based on this research are made to reconstruct the ecological environment of the wetlands and return them to their previous state.

Research of the display question in the 3D pipeline management information system

Good visual effect and visualization of topological relation of pipeline are characteristics of 3D pipeline management information system. So display of 3D pipeline is one of the key issues to research in the design and development course of 3D pipeline management information system. This article researches how to display 3D pipeline with good effect and at high speed using coordinate transformation and clip plane in OpenGL. The result we realize has good effect and multi-level-details characteristics.

A design method for building a multi-scale navigation electronic map

The functions of successive display and intelligent zoom among objects at different scales have not been developed in existing multi-scale navigation electronic map software system. So, taken the multi-scale and multi-media characteristics into consideration, this paper discusses the design and development strategies of multi-scale navigation electronic map. The total structure is built from the view of software engineer, and the key techniques based on interpolation method are proposed in details for intelligent zoom of multi-scale road map. At last, a case in point is given to build a convenient and visual spatial information services platform for route design, route guide and route display.

Management of groundwater in Zhengzhou City, China

Quasi-three-dimensional numerical simulating and optimum management model was established for evaluating and managing groundwater resources in Zhengzhou city. Based on the coupling of simulating model with a planning model, an optimum management model of groundwater resource was established. Through optimum controlling of the groundwater seepage field, environmental problem caused by unreasonable extraction of groundwater in the study area was decreased to the minimum level, which supply scientific foundation for groundwater resource management in Zhengzhou city.

Research on evolution of land subsidence induced by nature and human activity by utilizing remote sensing technology

In Northern China, main water supply is groundwater. In recent years, as the citys construction and development, long-term over-exploitation of groundwater has induced land subsidence which endangers the safety of human lives and properties. Because Beijing is a region seriously lack of water, five water sources for emergent events were built in order to meet the demand for urban water supply. Groundwater in such sources has been exploited in large-scale, high-intensity and concentratively, which will change groundwater system and result in related environmental-induced geological disasters. Shunyi District, as the place in which Chinas largest and most advanced Capital International Airport locates, meets more and more geological disasters such as land subsidence and ground fissure. Nature-human coupled factors impact on land subsidence progressing is focused in Shunyi District, the selected study area in this research. In the study, multi-scale remotely sensed imageries are utilized to extract human activity impact factors, especially in built-up areas. Hydrologic data is collected, and precipitation is defined as one of the natural factors. Comparison is made on relations between intensity change of accumulative ground subsidence and factors including precipitation, shallow groundwater exploitation amount, and land use in the period of 1990 to 2006. Meanwhile, contribution of nature-human impact factors on land subsidence is determined by AHP, and a Grey model is constructed in this research to forecast the intensity of ground subsidence in order to provide reference for prevention, control and slowdown on land subsidence.

Texture Analysis and its Application for Single-Band SAR Thematic Information Extraction

In this paper single-band and single-polarization Radarsat-1 SAR image is used to evaluate image classification with textural analysis. Firstly, the statistic information of sample were analyzed using semivariogram to determine the optimum parameters for textural extraction; Then four textures such as Homogeneity, Mean, Angle Second Moment and Entropy had been calculated based on GLCM, and the image data were processed using Support Vector Machine classification. The results show that the water and settlement areas are extracted accurately with accuracy 99.34% and 82.54%, and the SVM method has better extension ability for SAR image classification; Assisting with textural information, the image classification based on SVM has a obvious enhancement to original SAR, especially for some complex objects such as settlement areas(about increasing accuracy 18%).

A study on optical and SAR data fusion for extracting flooded area

This article proposes a method of fusing the optical data before the flood and SAR (synthetic aperture radar) data during the flood. The main goal of this study is to evaluate the capability of data fusion to combine the information from Landsat ETM image with Radarsat SAR image for water body and flooded area extraction. The Landsat ETM data will basically provide the information of landform and background information which includes the normal water extent. The Radarsat SAR data however was taken during flood will provide information mainly on water body extent and flooded area. In the result image, flooded area was significantly enhanced. We can distinguish the flooded area and normal water area easily.

Evaluating the effectiveness of routine water quality monitoring in Miyun reservoir based on geostatistical analysis

This study used geographic information system techniques and geostatistics methods to evaluate the effectiveness of routine water quality monitoring in the western segment of the Miyun reservoir in Beijing. Methodologies as well as the sampling design are evaluated. The single-layer evaluation and three integrated evaluation methods including principal component analysis (PCA), ordinary kriging (OK)_Mean, and Mean_Layers were used to validate the effectiveness of evaluation methods, and the effectiveness of each sampling design was validated by comparing their errors. Results indicated that, while a single-layer evaluation only shows the trophic state of water at a specific level, an integrated evaluation synthetically analyzes and evaluates the trophic state of the entire water body. Furthermore, results of the integrated analysis show that a PCA method is more accurate and can represent the trophic state of the entire water body. The OK_Mean and Mean_Layers methods are only able to represent the mean level for trophic state of the entire water body but cannot reflect local trophic state and distribution details. Although methods used in the routine monitoring of Miyun reservoir have some similarities to the OK_Mean and Mean_Layers methods, their range of errors and uncertainty are greater because of a lack of detailed spatial continuous information. The analysis on the number of sampling points shows that, within a certain range of error, minor changes of sampling points will have no obvious impact on the monitoring results. For the routine monitoring of western Miyun reservoir, using only three to five sampling points for monitoring is inadequate. According to our analysis, it is more appropriate to use at least ten sampling points for monitoring these areas.

Gis supported hedonic model for assessing property value in west Oakland, California

A hedonic linear regression model is constructed in this paper to estimate property value. In our model, the property value (sales price) is a function of several selected variables such as the property characteristics, social neighborhoods, level of neighborhood environmental contaminations, level of neighborhood crimes, and locational accessibility to jobs or services. Definitions and calculation of these variables are approached by using Geographic Information System tools. For improving estimation, gravity model is employed to measure both levels of neighborhood toxic sites and crimes; and a time-based method is used to measure the locational accessibility rather than simple straight-line distance measurement. This study discovers that the relationship between house value and its nearby highway is nonlinear. The methodology could help policy makers assess the external effects of a property. Our model also could be used potentially to identify the current and historic trends of development caused by neighborhood or environments change in the study area.

Dynamic monitor and analysis of Beijing wetland resource on the basis of RS and GIS

Supported by RS and GIS technology, combining the former achievements in scientific research and lots of field investigations, we used IRS image of 2000 and Landsat-TM images of 1984, 1989, 1992, 1996, 1998, 2002 and 2004 as information source, then, with the help of GIS and RS software, interpreted the images and built up Beijing wetland resource and ecological environment information system. On the basis of it, we can dynamic monitor wetland resource and wetland change trend of Beijing region in the past twenty years, including the wetland type, area and distribution; wetland biodiversity; wetland exploitation, etc. After all of these, analyze the actual state of wetland resource and the dynamic change of wetland in Beijing region. Keyword--GIS, RS, Beijing wetland resource, dynamic monitor