KAPPA Framework — Paper 2 Supplementary Validation Data

Supplementary validation datasets (three-point vs. midpoint spatial sampling, ERA5 vs. IGRA2 radiosonde surface temperature comparison, dual gradient computation, and tropical radiosonde kappa comparison) for the manuscript 'Computing the Atmospheric Refraction Coefficient from ERA5 Reanalysis Data for Precision Levelling and Total-Station Survey', submitted to the Journal of Surveying Engineering (ASCE). All four datasets (S2, S3, S5, S7) are complete as of this record. This version also includes the full supplementary document (Paper2_JSE_Supplementary.docx), hosted here per ASCE's policy of no longer accepting supplemental files directly. This record corrects a data error in the S7 tropical validation: two of the six comparisons used an incorrect IGRA2 station identifier (FMM00091334, Truk/Chuuk) in place of the intended station, Pohnpei (FMM00091348). Both comparisons have been recomputed against the correct station. The manuscript's tropical validation headline changes from 12.9% to 16.8% (six-comparison mean) as a result. Two earlier, unrelated corrections are also retained from a prior version: an arithmetic error in the S7 summary statistic, and a level-count error in the S5 dual-gradient summary. See README.md for full detail on all corrections.