# Sigma in GeoMipMapping

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schupf    221
Hello, I have one little question about the error sigma calculation in GeoMipMapping. According to the original De Boer paper you get ONE sigma error for each deleted vertex. But I am not sure if this is right. Look at this picture (LOD 0): If I make this grid 1 LOD level coarser I drop 5 vertices (1,9,10,11,19) and according to De Boer I get 5 Sigma's. But I think I have to calculate 6 error values Sigma: 1 Sigma for each edge that is dropped; i.e. edge (0,2), (0,18), (18,20), (2,20), (1,19) and (9,11). Because when I remove vertex 10 I delete 2 edges. So how should I do this with just 5 sigmas or am I right and I really need to calculate 6 sigmas (for each dropped edge)? Thanks!