Closed terrain depressions are geomorphic features that show scale invariance over the wide range of scales on which they occur, from metres to thousands of kilometres. They are also global features that are present on all continents. Morphometric analyses of these depressions are now possible because of the availability of global digital elevation models and advances in methods for mapping closed depressions. Here, a simple and automatic but efficient method is proposed for mapping closed terrain depressions. The GTOPO30 global digital elevation model, with a spatial resolution of around 1 km, was used to map the closed depressions of eight large test sites sampled from all inhabited continents. The identified and delineated terrain depressions include lake watersheds together with many other terrain depressions including deserts, karst terrains and rift valleys. A fractal analysis shows that South America and Central Africa have similar, and also the largest, fractal dimensions; Central Europe and North Africa have intermediate fractal dimensions; and North America, Central Asia, the Near East and Australia have similar, low fractal dimensions. The methodology proposed in this paper can be used to identify areas of interest for which a more exhaustive analysis, using digital elevation models with better spatial resolution, can be conducted.

封闭的地形洼地是地貌特征，在其发生的各种尺度上（从几米到几千公里），其尺度都保持不变。它们也是遍布各大洲的全球特征。由于全球数字高程模型的可用性以及绘制闭合凹陷的方法的进步，现在可以对这些凹陷进行形态分析。在此，提出了一种简单，自动但有效的方法来绘制封闭的地形凹陷。GTOPO30全球数字高程模型具有约1 km的空间分辨率，用于绘制从所有居住大洲采样的八个大型测试站点的封闭洼地。确定和划定的地形洼地包括湖泊分水岭以及许多其他地形洼地，包括沙漠，喀斯特地形和裂谷。分形分析表明，南美和中部非洲具有相似的分形维数，也是最大的分形维数。中欧和北非的分形维数中等。与北美，中亚，近东和澳大利亚的分形维数相似。本文提出的方法可用于识别感兴趣的区域，可以使用具有更好空间分辨率的数字高程模型来进行更详尽的分析。