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Based on the analysis of the construction principle of the rolling ball model, the paper has brought forward a TIN-DEM automatic generalization algorithm about the continuous scale expression of terrain shape. By taking the radius of the rolling ball as the analysis scale, this paper analyzes the deep-seated topographic information contained in the process of topographic scale change. If the sampling point contacts the rolling ball under a certain radius, the sampling point can be regarded as a flat terrain point under the radius of the rolling ball. Otherwise, it is a non flat terrain point. The contact between the sampling point and the rolling ball can be judged by the critical rolling ball radius. Then the flat terrain points under the large-scale radius can be deleted first. All sampling point of TIN-DEM are sorted according to the order from large to small of the critical Rolling Ball radius of the sampling point determined as flat terrain points. The sample point is processed in this order to ensure the stability of the processing results. The experimental results show that the algorithm can realize TIN-DEM automatic generalization, the generalization result retains the main features of the overall landform to the greatest extent, and the processing result is stable and reliable.
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