Observations and analysis of the cosmic microwave background (CMB) have led to stunning advances in observational cosmology. This is due on the one hand to an observational effort which has led to excellent data, but also to the theoretical simplicity of CMB physics. In a next (long term) step, cosmologists will try to repeat the CMB success story with observations of large scale structures (LSS), i.e. the distribution of galaxies in the Universe. The advantage of LSS data is the fact that it is three-dimensional, and therefore contains much more information than the two-dimensional CMB. The disadvantage is that the interpretation of the galaxy distribution is much more complicated than that of CMB anisotropies.

We describe a code, CLASSgal, which calculates galaxy number counts as functions of direction and observed redshift in linear perturbation theory. We estimate the sensitivity of future galaxy surveys to cosmological parameters, using the redshift dependent angular power spectra of galaxy number counts calculated with all relativistic corrections at rst order in perturbation theory