I've heard of those units that self erect but couldn't imagine just how they do it. Thanks for the video.
That's referred to as climbing over here. Technically not building itself. Still takes a crane and erection crew to put the crane up. Self erectors are smaller and are truly self erecting. Amazing machines really.
Referred to climbing or maybe even more common "jumping" here. As stated one still needs to set up the tower crane with a assist crane first. Usually as high as you can, we often went 120 feet because its considerably cheaper and less accident prone than jumping using a climbing tower section. If 200 feet of tower or less we just erected them with a assist crane to the full height.