【作者】 周霞；

【导师】 喻光明；

【作者基本信息】 华中师范大学 ， 地图学与地理信息系统， 2015， 硕士

【摘要】 作为自然地理要素重要组成部分的河网,不仅对水资源的开发利用有着重要的意义,而且对防洪减灾、环境保护等方面有着深刻的影响。流域河网的提取是水文分析及其相关问题研究的基础与关键,水系提取的精度也直接影响着流域水系相关研究的准确性。基于数字高程模型(DEM)直接提取水系和流域信息等方面的应用非常广泛,也为分布式水文模型的开发和应用奠定了基础。数字高程模型的分辨率与处理方式等因素对相关水系因子的提取存在一定的影响。本文以湖北省境内的四湖流域为研究区域,提出了一种河道偏移量检验方法来检验基于DEM水系提取的河道空间定位精度。利用Landsat OLI、Google Earth影像目视解译的结果来评价从SRTM DEM (90m)和ASTER DEM (30m)提取水系的河道偏移量。主要结论有：(1)集水面积阀值集水面积阀值的大小直接关系着水系提取精度的高低。集水面积阀值是水系提取准确程度的决定性因数,阀值愈低,提取水系愈密集：反之阀值愈高,则提取水系愈稀疏。随着集水面积阀值的增大,河道数和河网稀密程度、河流长度等随之减少。本文选取的阀值为3.29km2时,提取的河流水系与真正河网基本相吻合。(2)水系提取不同数据来源提取的水系,以及相同数据来源而不同方式提取的水系之间存在着较大的差异。基于SRTM DEM (90m)和ASTER DEM (30m)以及Landsat OLI这三种数据提取的水系在河流长度、河道数都不相同；Landsat OLI计算机解译和人工目视解译的河网差异比较大,河网密度分别是0.10km/km2和0.36km/km2。(3)河道偏移量的计算相对于30m分辨率Landsat OLI影像目视解译的结果,SRTM DEM遥感数据提取的河网平均河道偏移量为0.05-2.84km,ASTER DEM数据提取的水系平均河道偏移量为0.06-5.46km。研究结果同时表明,河道偏移量的大小与河流等级有关：河流等级越高,则河道偏移量越大；河流等级越低,则河道偏移量越小。显然,这是D8算法误差积累效应造成的结果。综合分析表明,相对而言,SRTM DEM (90m)提取的河道的精度较高,能够满足水文和水资源管理与研究的需要。更多还原

【Abstract】 Drainage networks are not only an important natural geographical factors, but also of vital significance on the development of resource and the flood control and disaster mitigation. The extraction of river networks from DEM data is a key to hydrological analysis and its relative studies. The accuracy of the extraction of drainage Networks is also directly affects the precision of the related research. Digital elevation model (DEM) is a widely used in watershed feature extraction. The way of extracting information directly of the network and watershed from digital elevation model is the foundation of the development and application of distributed hydrological model. The basic elements of DEM resolution and sampling methods have a certain influence on the extraction of water related factors.The present study takes Sihu basin which is in Hubei Province as the research area. A test method of positioning accuracy, the test of channel offset (TCO), is developed to test the error of extracted river networks in this study. Referring to the interpretation data of Landsat OLI images (with the resolution of 15 m), we test the extracted accuracies of river network from ASTER DEM (30 m) and SRTM DEM (90 m) by the TCO in Sihu basin respectively. The results show:(1)Drainage water threshold The results showed that the drainage water threshold was the key parameter for the extraction accuracy of water system, and the greater of drainage water threshold, the fewer and thinner of extracted water system; the smaller of drainage water threshold, the more concentrated of extracted water system vice versa. The number of river source, density of water system, class of river and the total river length decreased as drainage water threshold increased, but the main river length changed slightly. When threshold was 3.29 km2, water system extracted was relative coincident with the actual condition.(2) River extraction The result indicates that there are great differences in river extraction by using diverse data sources and using the different ways with the same data source. The results extracted from different data (SRTM DEM, ASTER DEM, Landsat OLI) are vary in channel length and stream number. The maximum channel density is between computer automatic interpretation and artificial visual interpretation, the channel density is 0.10km/km2 and 0.36km/km2.(3) Channel offset Referring to the interpretation data of Landsat OLI images (with the resolution of 30 m), we test the extracted accuracies of river network from ASTER DEM (30 m) and SRTM DEM (90 m) by the TCO in Sihu basin respectively. The results show that the channel offsets extracted from SRTM and ASTER DEM are about 0.05 km to 2.84 km and 0.06 km to 5.46 km. The result also shows that channel offset changes with the channel level in hierarchy of river network:higher the level of channels is, larger the channel offsets. We believe that it is an accumulative effect of the error from D8-algorithm.These errors lie on the range of permissible error in hydrology and water resources management at watershed scale. The extracted accuracy of river networks from SRTM DEM (90 m) is higher than SRTM DEM (90 m), meaning that it not only depends on the resolution of DEM, but also on the data resources.更多还原