International Marine Meteorological Archive (IMMA) is a data format for historical marine Met. observations (documented here). It is recommended by JCOMM, and has been adopted by the ICOADS; so it is generally the correct format to use for work on historical marine observations.
There are not many tools available for manipulating IMMA data. ICOADS provide a Fortran program. This is fast, but the limitations of Fortran mean that it's awkward to extend and unsuitable for converting IMMA data to and from other text formats. So, as part of a project to digitise some Royal Navy observations from the mid-20th century, I've produced some other tools:
- A Perl module for handling IMMA records.
- A web-based editor for visualising and editing IMMA files.