thank you for your reply, it was closed for 3 people who had answered and by mistake i deleted my post, also the post was for code. I posted something with a more general title to avoid discussions about my code, and be more understanding if someone want to be helped by that at his/her problem. Thanks a lot Mr. Patterson D, yes i have a DEM and i have also derived a slope layer in degrees. One solution is what you suggested i can select area>85o. Mr. Bakker X. I don't have lidar dataset if that is what you mean. The output i want to have is at the form of x,y,z. Theoretically why i cannot have cliff with 90o in my Dem, i cannot undestand that.