The subject intersection becomes one of the hot research topics recently. It is a new direction to integrate the GIS
technologies with Bibliometrics. The literatures concerned with geosciences normally involve some spatial related
information. In this paper, the spatial information of the study area and sampling or observing points was extracted. Then
these data were analyzed and presented by using the GIS technologies. The results indicate that there are big variations
of the spatial distribution. For the whole Qinghai-Tibet plateau, the degree of interest increase as follow: southwest,
northwest, southeast, and northeast. For the regions, Qilian Mountains, Qiangtang plateau, Qinghai-Tibet Road and
Qinghai-Tibet Railway, Qinghai Lake, and Sichuan-Tibet Road are the hotspot regions. There are differences of the
distribution characteristics in the different segments along the latitudinal direction and longitudinal direction. There is
transfer tendency from middle Qinghai-Tibet Plateau to northern Qinghai-Tibet Plateau. Most of sampling and observing
points are close to the traffic lines. The point numbers decrease quickly along with the increasing distance to the traffic
lines.
The subject intersection becomes a hot research topic recently. This paper tried to couple the Bibliometrics and
Geographical Information System (GIS) technologies for studying on the spatial information mining and visualization
from the Qinghai-Tibet Plateau's literature. All the literatures about Qinghai-Tibet Plateau research were indexed in the
ISI Web of Knowledge. The statistical tables about the authors were extracted from the papers by using the method of
bibliometrics. The spatial information of the author's countries was linked with the GIS database. The spatial distribution
was presented by the format of maps based on the GIS technologies. Comparing with the regular presentation forms of
the bibliometrical analysis, the spatial distribution maps can afford more abundant and intuitive senses for the users.
KEYWORDS: 3D modeling, Virtual reality, Navigation systems, Data modeling, 3D displays, Visualization, OpenGL, Molybdenum, Databases, 3D image processing
Virtual Reality provides a new approach for geographical research. In this paper, a framework of the Virtual Huanghe
River System was first presented, including four main modules - data sources module, 3D terrain database module, 3D
model database module and 3D simulation implementation module. Then the key technologies of Virtual Huanghe River
System and their applications were discussed in detail: 1) OpenGL technology, the 3D graphics developing tool, was
employed in Virtual Huanghe River System to realize the function of dynamic real-time navigation. 2) MultiGen Creator
was used to create the 3D model with real texture. 3) OpenGL and MO were used to make the mutual response between
3D scene and 2D electronic map available. The advantages of visualization, reality and locality in 3D scene and
macroscopic view, integrality and conciseness in 2D electronic map were integrated. And at the same time the
disadvantages of the losing direction in 3D scene and abstract and ambiguity in 2D electronic map were overcome.
The urban population density declines from Central Business District (CBD) to city edge. Some studies have explored
several mathematical forms to describe the relationship between population density and location. But these models
assume that the city is single center and the urban population decline with concentric circle format. It is difficult to
satisfy this requirement in actual cities. A distance variable, city edge distance, has been developed to solve the problem
in this paper. Using city edge distance can express multi-centered city situation. The irregular city is easily transformed
into a virtual concentric circle city. Then the Clark model and power exponential model are transformed into new format
based on the city edge distance. A case study indicates that the transformed formats could successfully simulate the
urban population density. But more applications are needed in different city types to validate and improve this distance
variable.
The northwest China, typical arid and semi-arid regions, is the first or second-degree sensitivity zones for global change. Monitoring vegetation change is an important method to study the impacts of global climate change. Time-series satellite remote sensing data make it possible to monitor vegetation at different spatial and temporal resolutions globally. A long time series of Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) data with 8x8 km2 spatial resolution and during 1982 to 2003 were used to monitor the vegetation cover in the northwest China. The monitoring results indicate an obvious greening trend exists. The precipitation and relative humidity have high correlations with the SINDVI. So the water condition is the most important factors for the spatial distribution of the SINDVI levels. The precipitation and temperature are the primary driving factors for inter-annual vegetation changes.
A method is developed to integrate topographical (elevation and slope) and climatic (precipitation and temperature) information with multi-temporal VGT images into a coarse scale land cover classification. The Normalized Difference Vegetation Index (NDVI), cumulated NDVI (SNDVI), Normalized Difference Water Index (NDWI) and the cumulated NDWI (SNDWI) were used in a two-step classification approach. The two steps encompass an unsupervised classification based on the ISODATA (Iterative Self-Organizing Data Analysis Technique) method, and a supervised classification based on a dichotomous hierarchical tree classification at the landscape patch scale. Results demonstrate the potential of the integrated method to estimate forest and grassland areas with VGT imagery. The method reduces confusion between different land cover classes with same spectral characteristics and slightly improves classification accuracy. 58% forest and 57% grassland were obtained for the Gansu Province. We suggest two main reasons for the high percentage of land cover misclassification: Confusion of the different land cover classes with same spectral characteristics and the spatial scale of observation unsuited for classifications of a highly fragmented land cover. The integrated data source approach is therefore limited to applications in regional land cover classification. The classification method could be improved in the critical value initialization of the classification tree.
The study area of this paper is Dingxi County, a typical loess gully-hilly region of the semi-arid regions. The land use maps in 1990 and 2000 were compiled from the Landsat TM images and other data resources. There are 9 kinds of land use types. The slope data derived of contour lines. Referring to some metrics of the landscape ecology, 10 metrics were selected or developed for quantifying the land use characteristic, monitoring the land use changes and analyzing the relationships between land use, land use changes and the topographical condition, governmental policies of the Dingxi County. Some conclusions were obtained. The selected metrics can quantify the land use and land use change in typical loess gully-hilly region, Dingxi County. The land use and land use change have good spatial distribution regularities in the slope grades. The governmental policies are the primary driving factors for the land use changes in our study area. The policies are reclaiming the slope farmlands and grassland into terraces, rainfall-collection works, and reforesting and regressing some sloping cultivated lands.
For the months July and August, 144 AVHRR images were pre-processed for 1990, 1992, 1994, 1996 and 1999 with a NOAA pre-processing chain (NOAA-CHAIN). A differencing method was applied to estimate the change of the NDVI between different years. The trend lines for six typical region’s NDVI average values in each year were subsequently analyzed. The vegetation condition of most of the regions in the Northwest of China is poor. From 1990 to 1999, most regions have negative NDVI difference values. Concomittantly, locally, some regions show positive NDVI differences, indicating that the vegetation conditions in the regions where an increase occurs, more or less improve. The most largely increasing region with regards to vegetation growth conditions mainly include the North and West of the Xingjiang Province, e.g., the Aertai Mountains, Tacheng, Kelamayi, north of Shihezi, the region between Shihezi and Kuerle, Yining, Akesu, Lanzhou and Dingxi of the Gansu Province. The trend lines of the first three typical regions show an upward path while those of the last three regions a downward one. Comparing the slopes of the six trend lines, it is indicated that the decrease in NDVI range is larger than the NDVI increase for the Northwest of China.
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