Designed to be a very light weight seismic reader that is easy and flexible.
Because of the history of SEGY standard there have been lots of places where people tended to use as default byte positions and data formats, For that reason we do minimal (no) checking to make sure the bit positions have the information that is expected.
We instead rely on highly flexible configuration files. the default segy 1 and segy 0 files can be extened and adapted with custom config files. If there is something that is missing that is needed you can use a constant and it will override whatever is in the byte positions.