Abstract: Slope units are widely used in the prevention and evaluation of landslide-based geological hazards, whose extraction and division are the primary target and important foundation for the risk assessment of landslide hazards. Considering the parallel boundaries and incorrect segmentation problems of the slope units extracted by traditional Geographic Information System (GIS) method, a slope unit extraction algorithm based on texture watershed was proposed, in which slope units were extracted by segmenting terrain images. Firstly, a Digital Elevation Model (DEM) image was obtained by the pretreatment of terrain data, and DEM texture features were extracted by gray level co-occurrence matrix. Then, the gradient image with gray level fused with texture features was calculated and segmented by marker-based watershed segmentation to accurately obtain mountain boundaries and watershed boundaries. Finally, combined with positive and negative terrains, the mountain objects were segmented by watershed segmentation to extract slope units. The experimental results show that the proposed method is pretty effective in segmentation for DEM images of different landform types and resolutions. Compared with traditional GIS method, horizontal planes and inclined planes can be segmented correctly, and the problem of parallel boundaries caused by filling of depressions can be effectively avoided through the proposed method.

Key words: slope unit, Digital Elevation Model (DEM), watershed algorithm, positive and negative terrain, texture gradient

摘要： 斜坡单元在以滑坡为主的地质灾害预防和评价中有着广泛的应用，其提取和划分是滑坡灾害风险评估的首要工作和重要基础。针对传统地理信息系统（GIS）方法提取的斜坡单元存在平行边界和误分割问题，提出了基于纹理分水岭的斜坡单元提取方法，通过分割地形图像划分斜坡单元。首先通过预处理地形数据得到数字高程模型（DEM）图像，利用灰度共生矩阵提取DEM纹理特征；然后计算融合灰度和纹理特征的梯度图像，对梯度图像进行基于标记的分水岭分割，使其能够准确获取山体和流域边界；最后，结合正负地形，对山体对象进行分水岭分割以实现斜坡单元的提取。实验结果表明，所提方法对不同地貌类型和分辨率的DEM图像都有良好的划分效果；相较于传统的GIS方法，该方法能够正确分割水平面和倾斜面，有效避免因洼地填平处理而产生的平行边界问题。

关键词: 斜坡单元, 数字高程模型, 分水岭算法, 正负地形, 纹理梯度