Abstract. Current and future galaxy surveys provide a wealth of information to constrain the cosmological parameters. I will show that considering only observable quantities, namely the redshift and angular position, we recover the same information of the 3D matter power spectrum. All the results have been obtained using CLASSgal, a code which computes the galaxy number fluctuations in linear perturbation theory, including all relativistic corrections. I will also present the relevant contributions to the bispectrum, computed from the galaxy number counts to second order.