This methodology can be enormously complicated. It is older than the other two methods and its structure is more rigid and well defined.
Given its heritage it is not surprising that huge amounts of paperwork and detail are generated using SSADM. SSADM deals with the whole project lifecycle and gives you a multi-step process to take you through each part of that cycle. SSADM is based on the more traditional approach to IT. It requires you to completely document and define all of the system requirements before you begin. SSADM-led projects are typically accompanied by huge project documents, which will be of largely notable interest.
SSADM favours a functional decomposition approach - the problem is split into ever-smaller functional chunks. SSADM does tend to build monolithic applications in the best 60s style which are hard to maintain and hard to integrate.
SSADM does work, but it is not the latest thing and it is not easy to do well. It does require expert analysts and practitioners, since it requires you to get everything right.
Next: Evaluation: OOD