Two letter code from ISO 3166 (refer to Annex A to S-57 Appendix A)
Authority (c2): (mandatory)
A string of two alphanumeric characters (refer to Annex A to S-57 Appendix A), e.g. German Bundesamt für Seeschiffahrt und Hydrographie = DE; US National Imagery and Mapping Agency = U1.
Source (c5):
Graphic e.g. plotting sheet, paper chart = graph
Report e.g. wreck report
= reprt