Cross-correlation analysis of potential H₂O signals in the transmission spectrum of GJ 1214 b observed with CRIRES⁺ in the nearinfrared. The method is illustrated for the night of 31 March 2022. We show the cross-correlation matrix in the Earth’s rest frame as a function of the velocity Doppler shifts applied to the template (horizontal axis) and the planet’s orbital phase (vertical axis). The results were obtained by using a template with 10× solar metallicity and a 10 mbar cloud deck. All useful spectral orders were combined. White lines mark the transit start and end times, while the yellow lines indicate the expected exoplanet velocities with respect to Earth.