Charts and Navigation

• Nautical Charts

• maps that show the makeup of the shoreline and seafloor
• provide water depths
• show locations of navigation dangers
• plot physical location to help navigation
• display anchorages

• Charts include:

• Chart number
• Latitude/Longitude
• Depths
• Hazards
• Buoys
• Distances
• Compass Rose
• Magnetic vs True North

• Latitude and Longitude: The Imaginary Lines

• Latitude

• horizontal lines, parallel to equator
• denotes N and S position

• Longitude

• vertical lines, perpendicular to equator
• denotes E and W position

• Measured in degrees, minutes, seconds, direction
• Locust Valley High School

• 40o 53' 16" N, 73o 35' 31" W

• Depths

• Represented by the numbers on the chart (in feet)
• Uses the average height of the lowest tide recorded at a tide station during the recording period

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• Bottom features and hazards

Marsh (Mar)	Rocks (Rks)	Grass (Grs)	Mud and Shells (M Sh)
Shipwrecks		Cable Area	Submerged Pilings (poles)

• Buoys

• Anchored floats serving as navigation markers
• Numbers on buoys increase as you come closer to port
• Some flash, some make sound
• Green buoys

• "cans"
• odd numbers

• Red buoys

• "nuns"
• even numbers

• As you return, keep the reds on the right.
• As you leave, the reds are on your left.

R N "4" Red "Nun" #4	G C "19" Green "Can" #19
GR C "A" Red/Green Mid-Channel	G "9" Fl G 2s Lighted: #9, Flashes (Fl) Green (G) every 2s

• Passing a boat

• Just like keeping red on the right when returning from sea…
• When passing a boat, keep its red light on the right of your view.

• Numerical Data

• 1 nautical mile = 1 minute of latitude
• Speed is measured in knots (kn)
• 1 knot is 1 minute of latitude per hour

• Compass Rose

• A circle divided into 360° numbered clockwise from true or magnetic north, printed on a chart to help determine the course of a vessel
• True north (North Pole) values are the outer ring
• Magnetic north values are the inner ring
• The variation information is contained in the compass rose closest to the ship's DR position

• DR = "Dead Reckoning"
• position calculated using a previous position (or "fix"), advancing position by estimated speed, times, course

• True bearing = Magnetic bearing + Variation

• add east variation or subtract west variation

• Tools of the Trade: Dividers

• Use dividers and latitude to measure nautical miles
• Determine distance
• Set the distance between prongs to one minute latitude
• "Walk" the divider from start position to end position
• "Pinch" to measure excess

• Tools of the Trade: Parallel Ruler

• Determine direction
• “The Walking Method”
• Line up points A to B
• Walk ruler up to compass rose

• Tools of the Trade: Sextant

• Used to measure angle between celestial object and horizon
• "Sighting" or "shooting" the object
• Can be used to estimate latitude (against sun) or longitude (against moon)
• Excellent precision

Project

Make a Map

Using standard NOAA coloring and abbreviations, create a map of a fictional area of your design. Include details like low tide depths, obstructions, land, streets, and an island. Maps may be hand- or computer-drawn.