The differences between elevations of the original and the disturbed DEMs range from 9.90 to −8.37 m (Table 3), which are within the reported error ranges (USGS 2009a), and the spatially averaged standard deviation of the errors is 1.24 m. In Table 3, the ranges of errors for every elevation class show that variations of the error are symmetric and greater in the mid-classes of elevation, 90–120 m. On the other hand, the minimum, maximum, and mean statistics of the error for the classes indicate that the SGS algorithm produced biased errors for lower and higher elevations. The errors tend to be positive and negative on lower and higher elevations respectively, while the overall average error, 0.04 m (median error is 0.00), is close to zero (Figure 7(b)). In other words, the disturbed DEMs overestimated and underestimated elevation on low and high elevation areas, respectively. It implies that, as desired, the correlation between error and elevation was considered in the algorithm.