Definition(en): ASEG-GDF2 (Australian Society of Exploration Geophysicists General Data Format Revision 2) is a data standard for the exchange and archive of geophysical data. Its primary purpose is to provide a consistent and self-documenting method for exchanging and archiving geophysical data between organisations with different hardware and software systems. For data to comply with the standard, it must be stored as a set of related ASCII files, which must include the following four filetypes as a minimum: File1.DAT, survey.DES, survey.DFN and survey.MET. The .dfn files enable the writing of code to enable to recovery of the geophysical data fields and their associated formats.