Navigation & Nautical Chart Production Flashcards

In chart production, the process of converting raw survey soundings to chart datum depth values requires:

Answer: Subtracting the water level (tide) at the time of measurement from the measured depth

Tide-corrected soundings are obtained by subtracting the observed water level above chart datum at the time of sounding from the measured depth below the water surface.

What NOAA publication defines the specifications and standards for nautical chart compilation and hydrographic surveys?

Answer: NOAA Hydrographic Surveys Specifications and Deliverables (HSSD)

NOAA's Hydrographic Surveys Specifications and Deliverables (HSSD) document defines all technical requirements for surveys that will be used in nautical chart production.

Electronic Navigational Charts (ENCs) used in ECDIS systems conform to which international standard?

Answer: IHO S-57 / S-100

ENCs are encoded in IHO S-57 format (with S-100 as the next-generation framework), which defines the data model, feature catalog, and exchange format for official electronic charts.

A 'scale of 1:80,000' on a nautical chart means that one unit on the chart represents:

Answer: 80,000 units of the same measurement in reality

A representative fraction of 1:80,000 means one unit measured on the chart (e.g., 1 cm) corresponds to 80,000 of the same units in the real world (80,000 cm = 800 m).

On a nautical chart, what does a magenta circle with a flashing light characteristic 'Fl(2) 10s 15m 12M' describe?

Answer: A light structure with group flashes of 2, 10-second period, 15 meters elevation, 12 nautical mile nominal range

The notation means: group flashing with 2 flashes per period, period of 10 seconds, light elevation 15 meters above MHWS, nominal range 12 nautical miles.

Which chart datum is used for the height of land features and bridge clearances shown on NOAA nautical charts?

Answer: Mean Higher High Water (MHHW)

NOAA references overhead clearances and land elevations to MHHW because it represents approximately the highest regular tidal water surface, giving conservative (safe) clearance values.