  Observability is a key aspect of the state estimation problem of SLAM,
However, the dimension and variables of SLAM system might be changed with new
features, to which little attention is paid in the previous work. In this
paper, a unified approach of observability analysis for SLAM system is
provided, whether the dimension and variables of SLAM system are changed or
not, we can use this approach to analyze the local or total observability of
the SLAM system.
