Rough and Bumpy DTM for vegetated/forest area

mrshaz

Hi, 

I have lidar data (UAV-Lidar) for an area consist of roads, buildings, and ground covered by shrub and trees. I did the auto-ground classification and then continue with creating DTM. However, the terrain model for area that covered by shrub/trees  looks too rough and bumpy, as in the picture. I've tried and error here and there like reclassify the ground using different parameter, reduce/increased the bins size etc. but nothing seems to work. I've also tried using the painting tools but smoothing them just doesn't seems right to me (the resolution for that area looks bad) and the bumpy is still there.

Anyone have an experience like this? or any suggestion on how to get smooth and clean terrain surface for area covered by trees/vegetation...

Thank you.