MARTA and LATTES : R&D projects for a new generation of high energy cosmic rays and gamma ray observatories

New generation of high energy cosmic and gamma ray experiments are presently in preparation, design or discussion. In charged cosmic rays a better understanding of the shower development and in particular its muonic component is clearly needed. In gamma rays the coverage of South Hemisphere is a must and a wide field of view Observatory complementary to CTA will be, soon or later, built. In the present talk it is explored the concept of hybrid detectors composed by RPCs and Water Cerenkov detectors in both contexts. The MARTA (Muon ARray for Tagging Air showers) project proposes to build in the next two years a small engineering array at the Pierre Auger Observatory. On the other hand, the LATTES (Large Angle Telescope for Tracking Energetic Sources) project proposes to design a wide field of view detector with improved sensitivity towards the lower energies, down to about 50 GeV. Its unique characteristics will allow to bridge the present gap between satellite-borne and ground-based observations.