Hydrographic surveys are conducted by and for the Office of Coast Survey to support safe navigation. Dangers to navigation are reported immediately by field parties for application to the nautical charts and publication in the Notice and Local Notice to Mariners.  The Office of Coast Survey requires the timely reporting of all potential dangerous features located during survey operations by field units conducting hydrographic surveys in accordance with the “NOS Hydrographic Surveys Specifications and Deliverables”.  

Dangers to navigation are inadequately charted natural and cultural features that a field hydrographer identifies as potentially dangerous to navigation. Submerged features with depths less than 11 fathoms (66 feet) in navigable waters are considered dangers to navigation as are items found to be significantly shoaler than charted, incorrect or uncharted clearances on bridges or overhead cables, and floating or fixed aids off position or incorrectly labeled. Hydrographers must also take into account the general vessel traffic including fishing and tour activities and largest scale chart produced for the area when making determinations regarding the potential danger of an identified item.

Danger to Navigation Reports are submitted by NOAA field units directly to the Marine Chart Division as soon as practicable after discovery and ahead of the complete survey package. Cartographers in the Marine Chart Division generate chart updates of these critical items, which are then forwarded to the U.S. Coast Guard and the National Geospatial Intelligence Agency (NGA) for inclusion in a Local Notice to Mariners  and U.S. Notice to Mariners.

RESOURCES

U.S. Coast Guard Local Notice to Mariners

National Geospatial Intelligence Agency Notice to Mariners