"Dangers to navigation" are inadequately charted natural and cultural features. Potential dangers may include:
- submerged features with depths less than 11 fathoms (66 feet) in navigable waters
- items found to be significantly shoaler than charted
- incorrect or uncharted clearances of bridges or overhead cables
- off-position or incorrectly labeled floating or fixed aids
When making determinations regarding the potential danger of an identified item, hydrographers must take into account the general vessel traffic, including fishing and tour activities. They must also consider the largest scale chart produced for the area.
NOAA field units submit "Danger to Navigation Reports" as soon as practicable after discovery and ahead of the complete survey package.
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."