The coordinate system definition file (coordsys.def) consists of four sections defining
Each section is starts with the name of the section enclosed in square brackets, e.g. [reference_frames]. Within each section are a number of definitions, one per line. For coordinate systems the definitions can be quite long. They may be extended over more than one line by ending each incomplete line with an ampersand (&).
Comments can be inserted anywhere in the file on lines starting with an exclamation mark (!). Blank lines and comments are ignored.
The basic structure of the file is thus:
[ellipsoids]
ellipsoid definitions
[reference_frames]
reference frame definitions
[coordinate_systems]
coordinate system definitions
[vertical_datums]
vertical datum definitions
The file can also contain additional sections defining textual information associated with coordinates systems, reference frames, and with transformations between them.
This is defined in sections
[reference_frame_notes] reference frame notes [coordinate_system_notes] coordinate system notes
Reference frame definition format
Coordinate system definition format