Current estimations of cosmological parameters depend often on assumptions about the cosmological model itself. The estimates of H0 or Ωm from CMB surveys, for instance, are valid only assuming a particular model, typically the standard ΛCDM. Similar model-dependent results are obtained also from analyses of large-scale structure. In some case it is however possible to combine observations in such a way to get estimates of physical
quantities that are valid regardless (to some extent) of the underlying model. Here I will discuss how one can determine the cosmological expansion rate H(z) and the deviation from Einstein gravity η by combining in a model-independent way several observational probes, from redshift distortions, to lensing, to matter clustering.