Research On Fenglin-Fengcong Surface Morphology Characteritics Based On Contour Trees

Fenglin-Fengcong is one of Karst geomorphological types whose morphological characteristics are typical and special. The individual and group morphological characteristics of different Fenglin-Fengcong not only are under comprehensive effects of various genetic conditions in karst landforms, but also could reflect the overall process of Karst landform development. The morphological characteristics of Fenglin-Fengcong has become one of the hotspots in Karst geomorphology research. Due to the limitation of data resolutions and analysis methods, existing research of Karst landform morphological characteristics paid more attention to quantitative description and mathematical statistics of a single terrain unit, and less concerned on their unique group structure characteristics. Contour Trees could reveal group nested features, associative features and spatial hierarchical structure features of landform objects. The DEM is used as basic data in this research,we built up Fenglin-Fengcong terrain unit's contour model and Fenglin-Fengcong contour tree structure, and selected a series of characteristic indicators and analyzed the morphological characteristics of Fenglin-Fengcong from multi-scale,multi-level,multi-angle the quantitative characteristics of terrain factors, terrain feature distribution and spatial combination were revealed from the perspective of individual and group respectively. The results obtained in this research have deepened the understanding of the morphological characteristics,landform evolution and spatial differentiation of Fenglin-Fengcong. The main work and conclusions are as follows:1. The construction of contour model and the extraction of terrain unit of Fenglin-Fengcong.On the basic of analyzing the morphological characteristics and distribution regulation of different Fenglin-Fengcong terrain units contour, this study came up with the contour model of different Fenglin-Fengcong terrain units, and expounded the concept and construction method of contour tree. Both peak and depression contour structure are composed of a group of concentric close contours. The peak cluster contour model is the structure of multiple groups of peak contour, and composite depression contour model consists of multiple sets of depression contour, and peak-depression model consists of peak and depression model. Meanwhile, this study designed and realized the extraction algorithm of terrain unit based on the morphological characteristics of contour. Contour tree method not only could achieve the extraction and classification of Fenglin-Fengcong terrain unit, but also could achieve the simplification of the Fenglin-Fengcong terrain.2. The quantification expression and extraction of Fenglin-Fengcong mophological indicators.According to scientific, systematic and accurate principles, and combined with the characteristics of Fenglin-Fengcong geomorphology and tree structure features, this study selected a series of morphological characteristics indicators of Fenglin-Fengcong,which were classified as the node attribute index and the morphological structure index.This study elaborated the mathematical description and its algorithm about morphological structure index and node attribute index, and analyzed DEM resolution effect on the construction of contour trees and the characteristic indicators expression.At the same time, we obtained the result that the DEM resolution has a greater impact on contour tree construction and its characteristic index expression.3. The research on surface morphological characteristics of Fenglin-Fengcong.On basic of analyzing the contour tree morphological structure of Fenglin-Fengcong, we have found that the morphological structure of Fenglin-Fengcong had different self-similar features in different landform types. In this thesis, we converted the semistructured contour to the chain structure of uniform length by the node serialization method, then analyzed the shape features of Fenglin-Fengcong from different scales, angles and levels. The result showed that whether the roundness coefficient or the tightness coefficient as a measure, the terrain shapes of the child nodes were more close to the circle than the parent nodes in different landform types. Complex geomorphic unit shape has gradually become a circular trend from the outside to the inside. Moreover, the spatial differentiation of the morphological structure indexes and Landform Planation Index of contour tree represents the indicators have a certain regularity in the spatial distribution: the terrain relief showed "low- high-low" from south to north, while the flattened degree showed the trend of "high - low- high" in the test areas; and the surface fragmentation gradually increased from west to east;Although the Fenglin-Fengcong of the study area were developed in the same time,they were distributed spatially and interspersed in space, showing the regional differences in the test area. This research was a useful exploration for the study morphological characteristics of Karst landforms.