Fig. 5 summarises the results of the Monte Carlo simulation. The mean of the 300 realisations has been calculated for the DSM, the slope derivative, and the weighted flow accumulation. The standard deviation for each derivative is also shown in Fig. 5. The standard deviation in the height values is in the order of 3.4–5.4 cm, which is indicative of the input error of 4.4 cm. The spatial distribution of the error is random. In reality the error in the DSM is likely to be spatially autocorrelated and is strongly related to the geometry of the camera network. An interesting avenue for future research is to derive the spatial distribution of the error from the bundle adjustment and run the Monte Carlo simulation with a spatially dependent error model.