针对露天矿坑坡面顶底线传统提取方法存在的低效率问题，提出了一种从露天矿坑DEM（数字高程模型，Digital Elevation Model）三维模型中自动提取坡顶底线的方法。首先对原始三维模型数据进行双边滤波预处理，进行去噪并保留特征点；其次根据高程值的标准差设定阈值后将DEM三维模型转化为灰度图像；最后采用梯度运算进行边缘检测，同时设计一个基于八邻域的搜索算法，将边缘像素按顺序连接成完整的台阶线。试验结果表明：自动化方法与传统人工提取方法相比，在保证提取精度的条件下，极大地提高了工作效率，最重要的是实现了提取过程自动化。该方法同样适用于DEM三维模型的地形特征线提取。

The slope top and bottom line plays an important role in open-pit mine mining design， production planning，calculation of stripping volume，road network planning，etc.Traditional extraction methods require the use of total stations and other equipment to rely on manual extraction，which is inefficient.In order to solve the problem of low efficiency of the traditional method of manually extracting the slope top and bottom line from the open-pit mine 3D model，a method of automatically extracting the slope top and bottom line from the open-pit mine DEM （Digital Elevation Model） 3D model was studied.The first step of the method is to pre-process the elevation data with up-sampling and bilateral filtering.The second step is to set a threshold，then according to the different elevation values of different regions in the DEM 3D model，different regions are converted into grayscale images with different pixel values.The last step is to perform gradient operation on the gray image，extract the edge pixels in the image，combine with an improved Zhang-Suen algorithm to extract the skeleton of the edge lines，and design a search algorithm based on eight neighborhoods to order the edge pixels and connect them into a complete contour line，and use the Douglas-Peucker algorithm for thinning to get the final step line.The experiment used the measured three-dimensional model data of an open-pit mine for testing.With the aid of a three-dimensional visualization software platform，the extracted step line is superimposed with the three-dimensional model of the pit，visually analyzed and compared，and the accuracy of the extracted results is judged.The visualization results show that compared with the traditional manual extraction method，the automation method greatly improves the work efficiency under the condition of ensuring the extraction accuracy，and most importantly realizes the automation of the extraction process.This method is also applicable to the terrain features of the DEM 3D model line extraction.