Photometric redshift distributions obtained using the ugri bands. The dashed black lines are the low- and high-density goals mentioned in Section 2, |$\bar{n}=10^{-4}$| and 3 × 10⁻⁴ h³ Mpc⁻³. The dashed red line is the BOSS CMASS sample. The solid blue line is the distribution enhanced by the ugri selection, it has a projected sky density of ∼340 deg⁻². The solid red line is the gri selection (projected sky density ∼350 deg⁻²). The solid green line is the ugr selection (projected sky density ∼400 deg⁻²). It shows the possibility of making a selection able to sample [0.6, 1.2] for a BAO experiment.