🔍 Key Concepts

• Fathom as a unit of depth (1 fathom = 6 feet) and how depth contours are shown on a nautical chart • How depth contour lines and soundings are symbolized on U.S. nautical charts • Difference between symbols made of dots versus dashes on charted depth curves

💭 Think About

• Look at how a 10-fathom contour is drawn on a standard NOAA or Admiralty chart—does it appear as a solid line, broken line, or a pattern of dots? • Compare the spacing and pattern of the options given (groups of dots versus continuous dots) with what you remember from chart symbols for depth curves. • Think about whether there is a special symbol just for the 10-fathom curve, or if it uses the same style as other depth curves with a particular line or dot pattern.

✅ Before You Answer

• Confirm from a nautical chart 1 (chart symbol guide) how depth contour lines are depicted, especially the 10-fathom line. • Check whether 10-fathom curves are shown as a continuous line or as spaced dot groups, and whether the pattern is regular or separated. • Verify that you are not confusing symbols for rock/obstruction soundings or scattered depth soundings with the symbol for a depth contour line.