Grid and Time Zones in Geography

Overview

This lecture explains the geography topic "Grid, Latitudes, and Longitudes," covering the grid system, important latitudes/longitudes, their uses, and time zones.

Introduction to the Grid System

• The grid consists of two types of lines (latitude and longitude).
• Latitudes run horizontally (east-west) and longitudes run vertically (north-south).
• The exact location of a place is determined where latitude and longitude intersect.

Latitudes

• Latitudes are imaginary lines that divide the Earth into North and South.
• The Equator (0°) is the most important latitude, dividing the Earth into two equal parts.
• Important latitudes: Tropic of Cancer 23.5°N, Tropic of Capricorn 23.5°S, Arctic Circle 66.5°N, Antarctic Circle 66.5°S, North Pole 90°N, South Pole 90°S.
• There are a total of 181 latitudes.
• They are parallel and form full circles; the largest circle is the Equator (Great Circle).
• Latitudes determine the Earth's different heat zones (Torrid, Temperate, Frigid).

Longitudes

• Longitudes are imaginary lines running from North to South.
• They are called meridians; the main meridian is the Prime Meridian (0°), passing through Greenwich, London.
• There are a total of 360 longitudes (180°E and 180°W), with the 180° longitude being the International Date Line.
• The main use of longitude is to determine time and time zones.

Time Zones and Standard Time

• The Earth is divided into 24 time zones; each zone differs by 15° longitude.
• Every country has its own standard meridian; India's is 82.5°E.
• Time calculation: east gain add (increase time), west lose subtract (decrease time).
• The day changes at the International Date Line (date gain/lose).
• The grid system enables accurate location and date/time determination.

Key Terms & Definitions

• Grid — A network of latitude and longitude lines used to pinpoint locations.
• Latitude — The angular distance of a place north or south of the Equator.
• Longitude — The angular distance of a place east or west of the Prime Meridian.
• Equator — 0° latitude dividing the Earth into two equal parts.
• Prime Meridian — 0° longitude passing through Greenwich.
• Parallels of Latitude — Parallel lines of latitude.
• Meridians of Longitude — Straight lines of longitude.
• Great Circle — The largest circle passing through the Earth's center (like the Equator).
• International Date Line — 180° longitude where the date changes.

Action Items / Next Steps

• Practice by drawing diagrams of latitudes and longitudes.
• Memorize the degrees of all important latitudes and longitudes.
• Solve examples of time calculation (east gain add, west lose subtract).