A h77t file extension is related to the Marine Geophysical Data Exchange Format.
H77T file extension - GEODAS MGD77T header data
What is h77t file? How to open h77t files?
File type specification:
The h77t file extension is associated with the Marine Geophysical Data Exchange Format an exchange format for marine geophysical data (bathymetry, magnetics, and gravity).
The h77t file stores metadata for M77T data files used by GEODAS software.
The GEODAS software is obsolete.
This h77t file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.