Comparison of distances. The x-axis shows the distances obtained using the optical velocities from the HyperLeda database. The y-axis shows the distances obtained from the NED database, a combination of redshift-independent measurements and redshift distances. The red line shows the one-to-one relation. The arrow shows galaxies with distances above the limits of the figure but located at the position of the other axis values. The dashed grey lines show the volume limit criterion of the S⁴G of 40 Mpc.