Fuhrmann, P ATrumpf, Jochen2015-12-080020-7179http://hdl.handle.net/1885/36403The paper presents an in depth study of topics in geometric control pertaining to observer theory from a functional point of view. We give characterizations of several classes of subspaces, including observability, almost observability and reconstructibility subspaces. We solve completely the problem of spectral assignability for observer dynamics by generalizing Rosenbrock's pole placement theorem. These results are then applied to observer theory.Keywords: Geometric control; Rosenbrock's pole placement theorem; Spectral assignability; Computational complexity; Computational geometry; Dynamics; Optimization; Problem solving; Theorem proving; Control system analysisOn observability subspaces200610.1080/002071706006312632015-12-08