I tried to get a grid by interpolating LAS file using Ordinary Kriging. But the product grid has many pixels which values strongly stands out from average surface - I mean one pixel sinks nad spikes. I know that sinks can be easily filled with preprocessing modules, but I found removing spikes more complicated. Is there any automated way to remove them? For instance a module which could get rid of pixels with values that stands out from their neighborhood?
You can try Grid – Filter→DTM Filter (slope-based). There is a very clear instruction in document "pc_processing_with_saga.pdf" by mr. Volker Wichmann, that could help you. Link below :
It's on page 26, but in your case it's worth to read all.