Study On Weighted Terrain Position Index And Its Application

Form is the most direct expression of landform and an important research content in geomorphology.Digital Elevation Models(DEM)are primary data source for land-form classification while landform classification is also an important research content of Digital terrain analysis.As one of important morphometric parameters,topographic position index(TPI)has the advantages of small computation and simple implementa-tion.It has been widely used by many scholars in automatic classification of land-form.TPI is naturally very scale-dependent.The research focus of TPI was the influence of different window size,less attention was paid to the landform meaning of TPI,the utilization of spatial information in the window and the deep application in other fields still need to be explored.In this paper,the main study subject is landform,topographic position index weighting method is proposed for micro-landform classification,a landform classifica-tion method based on weighted topographic position index is designed.The visualiza-tion method of field drainage based on weighted topographic position index is proposed to expand the application of topographic position index.The main content and achieve-ment as follow:(1)Study on TPI.Firstly,the definition and calculation model of TPI were ex-pounded.The morphography meaning of TPI was explained in combination with the schematic diagram:local TPI is an embodiment of surface form,while the regional TPI combined with local TPI reflects the complexity of the surface.Then the TPI uncer-tainty caused by the analysis window size and elevation error were analyzed and mod-eled,the TPI weighting mechanism was explained at the same time.Finally,the TPI weighting strategy and calculation model were studied and constructed considering ter-rain correlation and terrain structure.(2)Classification of slope position form based on WTPI.A systematic account of landform classification methods and technical features based on geometric thresholds were discussed,the suitable window size of TPI was studied.A WTPI-based slope posi-tion form classification scheme is constructed.A DEM of Nenjiang River Basin was used to classify the landform.The results showed that WTPI has scale stability com-pared with TPI,and has little change with the analysis window size.The WTPI landform classification method in this study area is reasonable.(3)Drainage visualization enhancement based on WTPI.The visual enhancement method of field drainage based on WTPI and slope was studied according to thier shape characteristics and morphometry features contents including color scheme design,pro-jection shadow processing and TPI window size setting for visualization.The results showed that compared with high resolution orthophoto and hillshade,many types of drainage in the study area can clearly identified by shading map produced by this scheme,which is a powerful complement to the drainage visualization method.