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

TPXO is a series of fully-global models of ocean barotropic tides, which best-fits,
in a least-squares sense, the Laplace Tidal Equations and assimilated data.
To refer to our models/software in your publications please use the citation:
Egbert, Gary D., and Svetlana Y. Erofeeva. "Efficient inverse modeling of barotropic ocean tides."
Journal of Atmospheric and Oceanic Technology 19.2 (2002): 183-204.

TPXO is copyrighted by the State of Oregon acting by and through the State Board of
Higher Education on behalf of Oregon State University, an educational institution
having offices at 312 Kerr Administration Building, Corvallis, Oregon 97331-2140
(hereafter, OSU) and ownership of all right, title and interest in and to the Software
remains with OSU. By using or copying the OTIS/OPTS/TPXO User agrees to
abide by the terms of this Agreement.

Converted into spherical harmonics by Torsten Mayer-Guerr