General information:   https://ifg.tugraz.at/downloads/ocean-tides
Format description at: https://ftp.tugraz.at/outgoing/ITSG/oceanAndAtmosphericTides/README.pdf

Reference paper:
Hart-Davis M., Piccioni G., Dettmering D., Schwatke C., Passaro M., Seitz F.:
EOT20: a global ocean tide model from multi-mission satellite altimetry.
Earth System Science Data, 13, 3869–3884, doi: 10.5194/essd-13-3869-2021, 2021.

Converted into spherical harmonics by Torsten Mayer-Guerr.