In this paper, we propose an improvement on the hierarchy method by using variable window size method to generate TIN (Triangulated Irregular Network) from DEM (Digital Elevation Model). We calculate the inclination on an area to choose appropriate window size depending on type of the surfaces. By dividing the whole image into smaller window size that is different depending on type of the surfaces, and evaluate the grid points inside, we can interpolate the all grid points by using a small

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... r of important grid points. We evaluated this proposed method by calculating the processing time, and also compared the regenerated DEM from TIN to the original DEM to know the elevation's differences in RMSE for keeping the performance of the hierarchy method. As the result, the elevation's differences in RMSE become small when using this proposed method.