Study On Extraction Of Topographic Information And Its Application Based On DEM Model

GIS is spatial information system started in 1960', which collects, reserves, manages and analyzes the spatial data. Two-dimensional projection of GIS destines disability in describing the three-dimensional phenomenon. DEM is the most important spatial information material of geographical dataset of GIS and also the core data of analysis on three-dimensional terrain. In this paper, takes Duolun county as an example, DEM of three-dimensional of study area is set up by using topographic map of 1:50000scale as data source, superposition with data of land use and vegetation cover, at last application of topographic information on spatial pattern of landscape, risk assessments of soil erosion, analysis of river system and topographic fluctuant degree are analyzed. Conclusions as follow:(1) Distribution law of topographic fluctuant degree of Duolun County is systematically analyzed from proportion structure, spatial distribution and height characteristic. According to the proportion structure, hills of study area, fluctuant degree are between 20 and 200 meters, occupy the biggest area, proportion of which is 82.90 percent; on spatial distribution, most part of the plain, fluctuant degree are between 0 and 20 meters, distribute northwest boundary area; the hill landform between 20 and 200 meters are the main study type and distribute in whole study area. And mountainous regions, fluctuant degrees are higher than 200 meters, distribute sporadically in the southeast of study area. With the increase of elevation, topographic fluctuant degree has gradually increasing trend. And there is an inflexion at the height of 1250 meters.(2) Superposition of DEM and land use distribution map of Duolun County indicates that distribution of landscape pattern has the character of slope and elevation. On distribution of elevation, there are more rivers and lakes and less landscape type on the district below 1200 meters; Each landscape types distribute more between 1200 and 1400 meters; Gravel land of uncovered rock and hill distribute most between 1400 and 1600 meters; Rural residential area and sand land distribute less higher than 1600 meters. On slope, there are more reservoir, puddle and pond and urban land in 0 to 5 degree slope zone; each type of landscape distribute evenly in 5 to 15 degree slope zone; In 15 to 35 degree, proportion of Gravel land of uncovered rock is most, 49.68 percent of the landscape; above 35 degree, there is few type of landscape, which distributes less. Because of the few area of the plainly land, the proportion is only 0.003 percent, each type of landscape distribute less; each type of landscape distribute evenly on other four slope.(3) Vegetation coverage is estimated on the base of NDVI by using RS image of Landsat TM in 1995 and 2005 of the study area. According to ministerial standard of ministry of water resources, risk of soil erosion of Duolun County is assessed by the grade of Vegetation coverage and slope. The results show that Heishanju town has the higher risk of soil erosion than other towns in Duolun County, Xigangou country and Shiwuhao country are secondary. Distribution law of risk of soil erosion in 2005 is similar to 1995, risk of soil erosion of Heishanju town, Xigangou country and Shiwuhao country are higher than other areas all the same.(4) Drainage network density is calculated by confirming threshold of runoff converged area of study area and picking up water system of seasonal river of study area; According to distribution law of drainage network density of seasonal river of Duolun county, contribution rate of each towns of Duolun County to sand source of Beijing and Tianjin. The results show that drainage network densities of Caishanmu country and Duolun town are the biggest.