Cross-checking of redshifts derived from different methods. Panel a: Spectroscopic redshifts from DESI versus redshifts from other literature. Panel b: Spectroscopic redshifts from SDSS versus redshifts from other literature. Panel c: Spectroscopic redshifts from DESI versus spectroscopic redshifts from SDSS. Panel d: Spectroscopic redshifts from DESI versus spectroscopic redshifts from SDSS after excluding data points with offsets larger than 0.1, representing the most reliable subset of our final sample. In each panel, grey points represent the original data, the red diagonal dashed line shows the 1:1 relation. The two blue dashed lines mark the region 1.6 < z < 1.7 on the vertical axis, where DESI redshift measurements show known systematic issues. The two black dashed lines mark the region where |∆z| < 0.1; most data points fall within this region, indicating that the redshifts from the two independent measurements are largely consistent.