Gaia and LSST are two projects that will perform large, multi-epoch, surveys of the sky. Gaia will provide an all-sky map with trigonometric parallaxes of unprecedented accuracy, proper motion and photometric measurements for about a billion stars with G magnitudes up to ∼ 20. LSST, on the other hand, will extend this map to r magnitudes up to ∼ 27 over half of the sky, detecting about 10 billion stars. In this presentation, we will summarise and compare the performances of the two projects, and identify their specific strengths and synergies. It will be shown how the two projects are complementary, Gaia mapping the Milky Way's disk with unprecedented detail, and LSST extending this map to objects located up to the edge of the Galactic halo. A specific focus will be given to the question of multi-epoch observations of these projects and their respective performances.