Comparison between the coverage of the parameter space for stars in the training sample using the original GALAH data (in purple, left panels), the original APOGEE-2 data (in blue, middle panels) and the parameters transformed from the GALAH into the APOGEE-2 base by the SPECTROTRANSLATOR algorithm (in orange, right panels). The contours in the right and middle panels depict the 1, 10, and 100 stars per bin limits in the selected GALAH DR3 catalogue (refer to Section 3.1.1) and APoGEE DR17 (refer to Section 3.1.2), respectively.