topic 2 5 latitude longitude · the latitude/ longitude earth point locating system operates by...

LATITUDE/LONGITUDEMr. Rocco

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THE LATITUDE/ LONGITUDE EARTH POINT LOCATING

SYSTEM OPERATES BY USING STAR

ANGLES

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LATITUDEDESCRIBES YOUR LOCATION NORTH OR SOUTH OF THE EQUATOR IN DEGREES (0-90)

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HERE’S HOW THE STAR ANGLE TELLS YOUR DEGREE OF

LATITUDE

LIGHT FROM POLARIS (NORTH STAR) SHINES ON EARTH AT NIGHT

People here look straight up…90o to their horizon..their latitude =90 deg north

Anyone along here sees Polaris 450 to there horizon..latitude=450 north

People here see the N Star 00above horizon…latitude=0O

LINES OF LATITUDE ARE ALSO CALLED PARALLELS

Altitude of Polaris and Latitude

WHAT IS THIS GUY’S LATITUDE ?

36 DEGREES

54 DEGREES

POLARIS

HORIZON LINE

WHAT IS HER LATITUDE ?

320

580

900

LINES OF LATITUDE ARE CALLED

PARALLELS…REMEMBER “LAT IS FLAT”

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49th Parallel?

• The 49th parallel of north latitude forms part of the international boundary between Canada and the United States

• The 38th parallel divides North Korea from South Korea

• The 17th parallel divided Vietnam up until 1975

LONGITUDEDESCRIBES YOUR LOCATION EAST OR WEST OF THE PRIME MERIDIAN IN DEGREES(0-180)

LINES OF LONGITUDE ARE ALSO CALLED MERIDIANS

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ALL LONGITUDE LINES RUN FROM THE NORTH POLE TO THE SOUTH POLE.

00 LONGITUDE ,ALSO CALLED THE PRIME MERIDIAN ,RUNS THROUGH GREENWICH, ENGLAND

HERE’S HOW IT WORKS

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THE EARTH SPINS FROM WEST TO EAST 150 /HOUR

360024 HRS= 15 0/HR

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REMEMBER THIS NUMBER!!!

TO DETERMINE YOUR LONGITUDE YOU MUST:

1. DETERMINE THE TIME DIFFERENCE BETWEEN WHERE YOU ARE AND GREENWICH

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2. MULTIPLY THE TIME DIFFERENCE BY 150 (THE EARTH ROTATES FROM WEST TO EAST 150 HOUR)

3. IF YOUR TIME IS EARLIER THAN GREENWICH TIME YOU ARE TO THE WEST…IF LATER IN THE DAY YOU ARE EAST

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WEST EAST

PRIME MERIDIAN

0 0LONGITUDESOLAR NOON

A. 7 AMB.10 AM C. 2 PM

D. 6 PM

THE LATITUDE OF: A= 75 DEG WEST B=30 DEG WEST

C= 30 DEG EAST D= 90 DEG EAST

EARTH SPIN

WHAT IS YOUR LONGITUDE IF:

1.IT IS SOLAR NOON AT YOUR LOCATION AND 10AM ON THE PRIME MERIDIAN?

THE TIME DIFFERENCE IS 2 HOURS…2X150=300

YOU ARE LATER IN THE DAY SO YOU ARE EAST OF THE PRIME MERIDIAN…300 E.LONGITUDE

• IT IS 6PM IN GREENWICH AND SOLAR NOON AT YOUR LOCATION. What is your longitude?

• 900 WEST

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3. IT IS 8AM IN GREENWICH AND 3 PM WHERE YOU ARE

1050 EAST

4. YOUR TIME IS 2AM AND IT IS NOON IN GREENWICH 1500W

Hold the instrument vertically and point it toward the celestial body. Sight the horizon through an unsilvered portion of the horizon mirror. Adjust the index arm until the image of the sun or star, which has been reflected first by the index mirror and second by the silvered portion of the horizon mirror, appears to rest on the horizon. The altitude of the heavenly body can be read from the scale on the arc of the instrument’s frame.

Sextant?

GMT: Greenwich Mean Time?

How specific can degrees go?

• To zoom in to a specific point on earth, lat/long narrow down to minutes and seconds

• 1O = 60‘ (minutes)• 1’ = 60“ (seconds)• EX: 73O 30’ 00” W = 73.5 O W

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