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Advanced Navigation
Latitude by Polaris
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Objectives
1. Gain an understanding of how the
observation of a celestial body yields a
latitude line. 2. Be familiar with the procedure
of determining latitude in the Northern
Hemisphere by the observation of Polaris.

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YOU ARE A SHIPWRECKED SAILOR ON A LOST ISLAND
???
WHAT ARE YOU GOING TO DO??
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THE PROBLEM NOW IS

• HOW TO DETERMINE
• YOUR LATITUDE

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THERE ARE TWO EASY WAYS TO GET THE LATITUDE

• Latitude By Polaris
• Local Apparent Noon

THESE TWO WAYS ARE SPECIAL CASES OF THE
NAVIGATION TRIANGLE
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I WILL USE LATITUDE BY POLARIS
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POLARIS
G P
NORTH POLE
.
ZENITH
EQUATOR
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POLARIS
.
CO-LATITUDE
CO-ALTITUDE
EQUATOR
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IN OTHER WORDS
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POLARIS
IMAGINE YOU ARE AT THE NORTH POLE
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POLARIS
ALTITUDE 90º
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POLARIS
IMAGINE YOU ARE AT THE EQUATOR
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POLARIS
ALTITUDE 0º
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THERE IS A DIRECT RELATIONSHIP BETWEEN THE
ALTITUDE AND THE LATITUDE
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Pn POLARIS
Altitude Ho
Observers Zenith
COLATITUDE COALTITUDE
Celestial Horizon
Observers latitude
Celestial
Equator
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Pn POLARIS
Observers Zenith
Altitude Ho
90º-lat
90º- Ho
Observers latitude
Celestial Equator
Celestial Horizon
Observers celestial meridian
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Latitude by PolarisBasic Steps

• 1. Determine local time of observation and DR
  position.
• 2. Convert your Local time to GMT.
• 3. Obtain Total GHA.

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Latitude by PolarisBasic Steps

• 4. Add or subtract your DR Longitude to get LHA
  exact.
• 5. Convert Hs to Ha.
• 6. Apply refraction correction.

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Latitude by PolarisBasic Steps

• 7. Enter Polaris Tables
• - Find A0 (use LHA Aries)
• - Find A1 (same column, use Latitude)
• - Find A2 (same column, use month)
• - Find Azimuth (same column, use
  Latitude)

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Latitude by PolarisBasic Steps

• 8. One degree must be subtracted
• from the sum of all corrections
• to get the total correction.
• 9. Apply this correction to Ha to get the
  observers Latitude.
• 10. Compare the gyro bearing to Azimuth to
  determine gyro error.

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Questions?
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Compliments of Curtis Senior High School NJROTC