1. Marine Charts and Navigation
Oceanography
2014

2. Earth Coordinate System
Latitude
Parallels of arc
0º-90º N-S from the equator to poles
1º = 60’ (1’=60 sec)
small circles
Longitude
Meridians of angle
0º (prime meridian) -180º E-W pole to pole
Prime meridian is measured at Greenwich England
great circles

3. Marine Charts Water depths
Configuration of the shoreline in coastal waters
Navigational lights, buoys, landmarks
Chart title block
Nature of the bottom (hrd, rky, g, sh, s, co)
North is the top, latitude scale on side, and longitude on top and bottom
Many charts cover less than a 1º of lat or long, so be careful when “fixing” a position

4. Units of Distance Statute vs. nautical miles
1 nautical mile = 1’ of latitude
1 nautical mile = 1.15 statute miles
1º of latitude = 60’ = 60 nautical miles
1º = 60 nautical miles = 69 statute miles
Use a drafting compass or dividers and spread points to apply to chart bar scale to determine distance

5. Units of Speed
Knot = 1 nautical mile/hour
1 knot x 1.85 = km/hr

6. Plotting a Course Magnetic vs. true (geographic) North
Use the “Compass rose” on the chart
The compass is graduated from 0º-360º and broken into 32 points on the compass
Cardinal points (0, 90, 180, 270 degrees)
Intercardinal points (northeast, southeast, southwest, northwest)
Cardinal-intercardinal points (ie. east northeast = 67.5º and south southeast = 157.5º)

7. Cont’ Course Intended direction of travel Expressed in degrees
However, influenced by winds, currents, and pilot error
Heading
The direction in which the ship is actually traveling regardless of prescribed course
Bearing
Direction from one point to another
Expressed as an angle from North
Traditional expressed as relative parts of the vessel

8. Time and Earth’s Rotation
Earth rotates on its axis once in 24hrs = day
Each rotation is 360º = 24hrs
Longitude 0º (prime meridian at Greenwich England) when sun is directly overhead is 12:00 noon
Therefore at 180º the time is 12:00am (midnight)
Therefore, every 15º of longitude E or W of Greenwich = 1 hour of time (Zulu or Z. time)
360º/24 = 15º

9. D.R. Navigation Also known as Dead Reckoning or “Ded” Reckoning
Method of navigating using the following from a KNOWN position:
Time
Speed
Distance
Direction
Note: Does not account for error or currents

10. Formulas Distance = Speed x Time Speed = Distance / Time
Time = Distance / Speed
Use 60 D = S * T (for minutes) D S T