CHAPTER – 1 LATITUDES ,LONGITUDES, Standard Meridian of India, International Date Line (IDL) (General Aspects of Geography) for all Competitive exams

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 LATITUDE:

• Latitude is the angular distance of a point on the Earth’s surface, measured in degrees from the center of the Earth.

• It varies from 0° (Equator) to 90° North and 90° South.

• Latitudes are circular lines parallel to the Equator. They are called Parallels of Latitude.

• Latitudes are also called Temperature Coordinates because temperature decreases from the Equator towards the poles.

 Important Lines of Latitude:

• Equator – 0°

• Tropic of Cancer – 23½° N

• Tropic of Capricorn – 23½° S

• Arctic Circle – 66½° N

• Antarctic Circle – 66½° S

 Heat Zones of the Earth:

1. Torrid Zone (Tropical Zone):

   • Between Tropic of Cancer and Tropic of Capricorn.

   • Receives maximum heat.

   • Sun is overhead at least once a year.

2. Temperate Zones (Mild Zones):

   • Between Tropic of Cancer & Arctic Circle (North).

   • Between Tropic of Capricorn & Antarctic Circle (South).

   • Have moderate temperature.

3. Frigid Zones:

   • Between Arctic Circle & North Pole.

   • Between Antarctic Circle & South Pole.

   • Very cold regions.

     

     
     
     
     
     

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 LONGITUDE:

• Longitude is the angular distance measured in degrees east or west of the Prime Meridian (0°).

• It varies from 0° to 180° East and 0° to 180° West.

• Longitudes are also called Meridians.

• Each longitude is a semicircle running from North Pole to South Pole.

• Longitudes are called Time Coordinates.

 Time Calculation:

• 1° longitude = 4 minutes

• 15° longitude = 1 hour

 Prime Meridian:

• Located at 0° longitude.

• Also called the Greenwich Line.

• Passes through Greenwich near London.

• Determines Greenwich Mean Time (GMT).

🇮🇳 Indian Standard Time:

• Based on 82½° East Longitude.

• This is the Standard Meridian of India.

  

  

  
  
  

  
  

   Standard Meridian of India:

  • The Local Time at the Standard Meridian is taken as the Standard Time for the whole country.

  • In India, 82½° East Longitude is treated as the Standard Meridian.

  • It is known as Indian Standard Time (IST).

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   International Date Line (IDL):

  • The International Date Line is an imaginary line drawn approximately at 180° longitude.

  • It avoids crossing major land masses.

  • It passes through:

    • Arctic Ocean

    • Bering Strait

    • Pacific Ocean

    • Antarctica

    • Fiji

    • Tonga and other islands

   Importance of International Date Line:

  • It is the longitude where the date changes by one day.

  • If a traveller crosses:

    • From East to West → Loses one day

    • From West to East → Gains one day   

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   Do You Know?

  • The midday sun never shines overhead beyond the Tropic of Cancer (23½° N) and the Tropic of Capricorn (23½° S).

  • 180° East and 180° West longitudes are the same line, called the International Date Line.

   Time Zones in Some Countries:

  • Russia has 9 time zones.

  • China has 1 official time zone (though geographically wide).

  • USA has 6 main time zones (Atlantic, Eastern, Central, Mountain, Pacific, Alaska, Hawaii-Aleutian).

  • Canada has 6 time zones.                                                                                                           Disclaimer:

    This study material is prepared for educational and competitive exam preparation purposes only. The content is simplified for easy understanding and may be referred to along with standard textbooks for detailed study.