Partial observability of finite dimensional linear systems

In this work, we consider the partial observability problem for finite dimensional dynamical linear systems that are not necessarily observable. For that purpose we introduce the so called ”observable subspaces” and ”partial observability” to find a way to reconstruct the observable part of the system state. Some characterizations of ”observable subspaces” have been provided. The reconstruction of the orthogonal projection of the state on the observable subspace is obtained. We give some examples to illustrate our theoretical approach.