Correlation between parameters of the wCDM model, marginalised over the galaxy bias for a DESI-like survey. Top panel: angular galaxy clustering (D_g), central panel: ARF alone (D_z), bottom panel: combination of both observables (D_g,  z). We find that D_z show different correlations compared to D_g. The combination of both helps significantly to break degeneracies, as we can see in (panel c).