Omnidirectional Gravitational Wave Detector with a Laser-Interferometric   Gravitational Compass
  Based on the Szekeres-Pirani gravitational compass we suggest the addition of a fourth, non-coplanar mass/mirror to the presently existing laser based gravitational wave observatories, enabling them to operate omnidirectionally, to filter out ambiguous interpretations and to point out the direction of the gravitational wave source. 
M.D. Maia, Ivan S. Ferreira, Claudio M. G. Sousa, Nadja S. Magalhaes   and Carlos Frajuca
gr-qc