The National Ocean Service's (NOS) Hydrographic Manual, Fourth Edition (1976), contains specifications and procedures for hydrographic surveying and includes updates through Change Number 3 (June 1981). This manual has been superseded by the 2008 editions of the “NOS Hydrographic Surveys Specifications and Deliverables” and the "NOS Field Procedures Manual." Download: National Ocean Service Hydrographic Manual, Fourth Edition (1976)