Navigation NAU 102 Lesson 6

Position, Distance & Direction Where am I? How far is it? Which way?

Position Shown relative to fixed object. E.g. 1 nm north of Chesapeake light

Position Shown by Lat/Long. (e.g. 36° 50.6’N 075° 31.2’W)

Position Plotting Lat/Long.

Position

Loran Hyperbolic system Long Range Navigation Based on time differences in received signals from Master and Secondary stations. Results in hyperbolic lines of position (LOP’s)

Loran

Components Master transmitting station Two or more Secondary stations Shipboard antenna and receiver Loran charts

Loran Chains

LORAN TERMINATED! U.S. LORAN operation has been terminated by the Department of Homeland Security Termination commenced on February 8, 2010 and continued through August 2010 Canadian LORAN operations have also terminated on both coasts The USCG has eliminated LORAN questions on license exams.

Loran Time Differences are displayed on a shipboard receiver.

Position Symbols DR position – half circle R-fix Visual fix – circle Electronic fix – Triangle Running fix – circle labeled “R-fix” Estimated position – square

Direction Different ways to measure/state direction. True direction – angle from true north (°T) Magnetic direction – angle from magnetic north (°M) Relative direction – angle from ship’s heading (°R)

Direction Direction is stated in degrees or points. e.g. 045°T vs. North East e.g. 315°R vs. 2 points to port

Direction Degrees N = 000° Counted clockwise from the reference line. E = 090° S = 180° W = 270° Stated in 3 digits

Direction 32 points in a circle 11.25° = 1 point Points

Direction N = 0 pts = 000° Cardinal Points E = 8 pts = 090° S = 16 pts = 180° W = 24 pts = 270° Boxing the Compass

Direction NE = 4 pts = 045° Intercardinal Points SE = 12 pts = 135° SW = 20 pts = 225° NW = 28 pts = 315° Midway between cardinal points

Direction NNE = 2 pts = 022.5° ENE = 6 pts = 067.5° ESE = 10 pts = 112.5° SSE = 14 pts = 157.5° Halfway between cardinal & intercardinal NNW = 30 pts = 347.5° WNW = 26 pts = 292.5° WSW = 22 pts = 247.5° SSW = 18 pts = ° Stated cardinal then intercardinal

Direction Remaining points N by E = 1 pt = ° Nearest cardinal or intercardinal point by the next cardinal point NE by N = 3 pts = ° NE by E = 5 pts = ° E by N = 7 pts = ° Etc., etc.

Direction Relative directions can be stated by degrees or points. e.g. 045° R or 4 points to stbd e.g. 315° R or 4 points to port

Direction Bearing Stated True, Magnetic or Relative Direction of one object to another e.g. stbd beam, fine on port bow, stbd quarter, 2 points abaft the beam, etc. Can be in Degrees, Points or Words

Direction

Bearing “To” vs. “From” A to B = 060°T A from B = 240°T

Direction You can convert between relative and true bearings. Relative Bearing + Ship’s Heading = True Bearing

Direction R + S = T R = T – S And S = T - R

Direction Example You are on course 170° T and you sight a vessel abeam to starboard. What is the true bearing of the vessel? R + S = T 90° + 170° = 260° T

Direction Example You are on course 250° T and on radar you detect a vessel at 125° T. At what is the relative bearing to the vessel?

Direction R = 125° - 250° = -125° R -125° R ??? 360° - 125° R = 235° R You are on course 250° T and on radar you detect a vessel at 125° T. At what is the relative bearing to the vessel? R = T - S If < 0, add 360°

Distance Measured using latitude scale on a Mercator projection chart. Use the scale at the mid-latitude of what you are measuring.

Distance

Introduction to Navigation Questions?