How to Use a Nautical Map

Nautical maps, or charts, are essential tools for any boater. Knowing how to use a nautical map allows the boat to safely travel through unknown areas. These charts not only detail the depth of the water but also reveal underwater and overhead obstacles that can affect the safety of the ship. Captains must be aware of the draw of the keel -- the depth of water the boat needs to float; the clearance height of the mast, including the radio or radar antennas, to prevent getting caught on bridges; and whether or not the vessel can handle the dangers of a shipping lane, before plotting the course.

Things You'll Need

  • Ruler
  • Pencil
  • Transparent protractor (with degrees)
  • Laminator (if desired)
  • Dry erase markers (if desired)
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Instructions

    • 1

      Lay out the map and identify the start and end point of the voyage. Circle both areas with a pencil to make them clearly identifiable.

    • 2

      Determine if the ship will be considered to be traveling seaward -- toward the sea -- or shoreward -- toward the shore. Make a note on the chart as to which direction will be traveled.

    • 3

      Make a note on the nautical chart of which color marker should be held to the starboard, or right, side of the boat. For seaward journeys all green colors, buoys and lights should be on the starboard side of the boat at all times. Shoreward journeys need to keep red colors, markers and lights on the starboard side.

    • 4

      Use a ruler and pencil to plot a path from the start point of the voyage to the end point, according to the starboard color required -- red or green -- and the depth required to keep the keel from dragging on the bottom. The depth is written in feet in small black numerals on the chart. The buoys and other markers are indicated by geometric shapes -- for example, triangles and cones -- followed by an indicator of the color (R for Red, G for Green and RG for Red and Green).

    • 5

      Go back over the planned route and look for any overhead obstacles -- designated as bridges and power lines. Read the clearance marking, which is abbreviated "CL" followed by a number. The number is the height of the object from the surface of the water. Adjust the route as necessary to avoid any overhead obstacles that will tangle with the ship's mast.

    • 6

      Look for any indicators of underwater obstacles -- pipelines, power lines, wrecks and reefs. The specific name of the obstacle will be written along with a number in red. This number is the depth the obstacle is at below the surface. Adjust the route as necessary to avoid any underwater obstacles that will tangle with the ship's keel.

    • 7

      Change the route, if necessary, so that it does not require the pass through any prohibited areas. Prohibited areas are labeled as such and are often marked with hatch marks on the map. These areas can include chemical or weapons dumps and protected areas and should be avoided at all costs.

    • 8

      Mark with an arrow all changes in direction on the path. Use the ruler to find the exact longitude and latitude of the point at which an adjustment must be made by using the graduated marks on the outside edge of the map. Make a note at each point of adjustment of the exact longitude and latitude.

    • 9

      Measure the degree of change in the ship's direction using a transparent compass and the degree scale on the chart. Make a note next to the longitude and latitude of the degree of turn needed to starboard or port -- left -- to keep the boat on the correct path.