RELATIVISTIC VERSUS NEWTONIAN FRAMES: EMISSION COORDINATES

Only a causal class among the 199 Lorentzian ones, which do not exists in the Newtonian spacetime, is pri-vileged to construct a generic, gravity free and immediate (non retarded) relativistic positioning system. This is the causal class of the null emission coordinates. Emission coordinates are defined and generated by four emitters broadcasting their proper times. The emission coordi-nates are covariant (frame independent) and hence valid for any user. Any observer can obtain the values of his (her) null emission coordinates from the emitters which provide him his (her) trajectory. Key words: null emission coordinates, location systems, causal class, positioning system, gravimetry. 1