Why do I get artifacts in slope/aspect calculation?

[rese_support]

When calculating the slope and aspect images from very high resolution DEM's (typically 1-10 m) steep slope gradients occur from one pixel to the neighboring pixel. This causes the slope pattern to be visible in the processed image. This can be avioded by using a filter size of 3-10 pixels for the slope/ aspect calculation to smooth the gradients. Sometimes and with low quality DEMs, the DEM needs to be smoothed by this filter prior to the calculation.