Panel a: typical distance uncertainty for the red clump as a function of distance. The red curve shows the expectation from a naive inverse parallax estimation, the blue curve shows the predicted uncertainties in the photometric distances in G band and for W1 this is shown by the green curve. The two vertical dotted lines indicate roughly the distances beyond which the photometric distances become more informative than parallax inversion for the two bands. Panel b: distribution of photometric uncertainty in W1 for the RC stars shows that σ_w1 ≪ 0.1, i.e. lower than the intrinsic dispersion in the absolute magnitude of RC stars in W1.