The Comprehensive Research Of Automatic Lineament Extraction From DEM

After 1950', DEM is extensive applied to survey,civil engineering,geology,mineral mountain engineering,the view building,road design,floodcontrol,agriculture,programming,the military engineering,aircraft andbattlefields imitated true and so on . In hydrology , since 1960', geographycharacteristic research extracted from DEM had begun, its high peak appearfrom 1980' to 1990', and its importance is the application to the foreignsoftware. In that realm, the previous research of 1980' is a less range ofresearch limited by the watershed and valleys to identify and extract. But itobtained speedy development from 1980' to 1990' when various method thatextract appeared watershed,the river boundary and the sub-river valley. In thelast few years, the point is changed from the one geography characteristicextraction to sub-watershed extraction, and the computing methods aredifferent. But all depend on the one geography character. Lots of problems aresoloved when the one geography character is extracted. In the last few years ,the local scholar investigated the shortcomings of the existing methods for thecomplex terrain DEM with depressions and flat areas, and proposes severalnew methods, namely, the classification and the merger of depressions, thevalid filling depression, the classification of flat areas, and the construction ofthe drainage direction based on the flow cost for the river valley plains. The useof extracting watershed overcame the creation of the parallel of river, falsecourse of river and strange course of river effectively, coming to the morereasonable and ideal result.According to the scrope of using line information, the extraction methodscan be divided into: the overall situation method and the partialmethod. The overall situation method includes the certain watermodel methods and the random water model methods, they use theoverall situation information to extract the line information. Thispaper studies the water model method to extract watershed andremittance basin systematically, and analysis Rho and the methodimproved. The partial method includes the method of hanging to cutto the face, the method of cut level to face and the method ofmatching the curved faces, they then use the partial informationto extract the line information. The chapter 5 of this paper makesintroduction of the basic calculation to use partial method forextracting the line information.The overall situation methods and the partial methods explainautomatic linement extraction method from hydrology and appearancemethod respectively, but both exist the certain blemish:(1) The overall situation methods use a lot of value, and try toclassify the grid point. But the definition of unreasonable spacepartition will produce the mistake of the partial classification,and then we can not get all network structure;the extraction iswatershed network, and it makes sure the drainage source and notvalley source. The method of making sure the valley source don'tmatch the physics character of the valley;the ability of permitingwrong is bad, and when the local geography is more complicated, thisway has certain limitation.(2) The partial method extracting the line information is drainagecharater ,and the ability of permiting wrong is bad and it issensitive to voice. The wrong DEM will result in the broken pointin valley line, and it makes influence to get the right result.Basing on the analysis of two kinds of blemishs, this paperintroduces automatic linement extraction method from hydrology andappearance method, and integrity extraction method basing on DEM.This method has the following characteristics:(1)making use of thedifferent space dimension obtions the valley network which matchthe physics character of the actual earth's surface;(2)we avoid touse of the value as far as possible, unless the value has the goodstability in the space;(3)we can get the whole valley network whichmatches the physics meaning, and it has the space fixed positioncharacter of the precision which can be used the calculation of thediagram and various parameters of valley.This method can be expanded,used to extract the other geography characteristics of the riverand automatic manufacture valley density diagram and the assistancecreation geography diagram;and it can be used for analysis of thefixed amount of the soil erosion,and then developping the spaceimitation of the geography process.Because the network of the valleyis the key to control various geography, this method has generaluse in different geography type;basing on dynamic extraction fromDEM, it also carry out dynamic graphics to reflect the variousenvironment.In order to perfect combining automatic linement extractionmethod to hydrology and appearance, this paper introduces AEDNM.This method is different from the previous methods in the approachof dealing with the sink-filling problem. It determines the flowdirection by searching upward from the catchment outlet and forma directed but non-loop graph based on the idea of combining thegraphic theory with hydrology.The proposed method guarantee thatthe generated river network is continuous and the sizes of thedelineated subcatchments are homogeneous.Through the whole exampleverification of the yellow river, it expressed that the method canbe used .Currently, we can also obtain the watershed structure quicklyand accurately,and they can remit to different densities of drainagenetwork according to the value of accumulated units. But the spacedifferentiation of DEM, the DEM data mode of production , and thedifferent geography features etc.make a certain effect to theextraction, and at the same time we select certain value which affectthe sizes of the flow area and the accurance need to be probing.Thispaper introduces Hydrology's tool function in ArcGis 9.0, and thisfunction can finish linement extraction,the valley division andthe hydrology information statisticses etc.The tool of variouscalculate ways come from the hardwork of numerous science andtechnology workers.This paper expects to provide some helps to other science andtechnology workers and make function that the brick leads the jadeby introducing automatic linement extraction methods.