Ch2 Geographic grid

What is a geographic grid?

The geographic grid is a framework made of criss-crossing lines of latitude and longitude.

Who created lines of latitude and longitude?

Eratosthenes, a Greek philosopher, created the lines of latitude and longitude. He also calculated the Earth's circumference for the first time.

What is the purpose of a geographic grid?

The geographic grid helps us locate places, similar to how coordinates work on a graph.

Define lines of latitude.

Lines of latitude are imaginary lines that connect places with the same latitude north or south of the equator. Latitude measures the angular distance of a place from the equator.

How are latitudes calculated?

Latitudes are calculated by measuring the angle a place makes with the center of the Earth. The equator is marked as 0°.

Why are they called parallels of latitude?

They are called parallels of latitude because they are parallel to each other.

Is the length of latitude constant? Explain with an example.

No, lines of latitude are not the same length. They get shorter as you move towards the poles. For example, at 60° latitude, the circle's length is half that of the equator.

Name the seven important lines of longitude with their degree

The important lines of latitude are: the Equator at 0°, the North Pole at 90° N, the South Pole at 90° S, the Tropic of Cancer at 23 1/2° N, the Tropic of Capricorn at 23 1/2° S, the Arctic Circle at 66 1/2° N, and the Antarctic Circle at 66 1/2° S.

What does the equator divide the earth into?

The equator divides the Earth into the Northern and Southern Hemispheres.

What are the uses of latitudes?

Latitudes help us find the location of a place north or south of the equator. They also help measure the distance from the equator and divide the Earth into heat zones.

What are the major heat zones of the earth?

The major heat zones are: the Torrid Zone between the Tropic of Cancer and Tropic of Capricorn (the hottest), the Temperate Zone between the Arctic Circle and Tropic of Cancer and Antarctic Circle (moderate climate), and the Frigid Zone between the Arctic Circle and North Pole and Antarctic Circle and South Pole (very cold).

Define lines of longitude.

Longitude is the angular distance of a place east or west of the Prime Meridian. Lines west of Greenwich are labeled W, and lines east are labeled E. All lines of longitude are the same length.

How many latitudes are there in 1° interval?

There are 181 lines of latitude at 1° intervals.

How many lines of longitude are ther in 1° interval?

There are 360 lines of longitude at 1° intervals.

Why are longitudes known as meridians of longitude?

Longitudes are called meridians because the sun crosses a longitude at noon.

What is anti meridian?

The anti-meridian is the 180° longitude line.

What is the distance between 1° of latitude and longitude?

The distance between 1° of latitude and longitude is 111 km.

Explain relationship of longitude with time.

The Earth rotates 360° in 24 hours, which means it covers 15° of longitude in one hour, or 1° of longitude every 4 minutes. If it's 12 Noon at 0° longitude, it will be 12:04 PM at 1°E longitude and 1:00 PM at 15°E longitude. To the west, it will be earlier. Remember: East-Gain-Add (EGA) and West-Lose-Subtract (WLS).

What does the prime meridian and anti meridian divide the earth into?

The Prime Meridian and anti-meridian divide the Earth into the Eastern and Western Hemispheres.

How is the local time calculated?

Local time is based on the position of the sun at noon. For each degree of longitude, the local time changes by 4 minutes.

What are time zones?

The Earth is divided into 24 Time Zones, each covering 15° of longitude. This helps avoid confusion. Countries like India have one Standard Time Zone, while countries like Russia, Canada, and the USA have multiple Time Zones.

Define standard time.

Standard time is a uniform time based on a central meridian, usually divisible by 7 1/2°. The Indian standard meridian is 82 1/2°, which passes through Mirzapur, Allahabad.

What is Greenwich mean time?

Greenwich Mean Time (GMT) is the time at Greenwich (0° longitude). If it's 12 Noon at Greenwich, it will be 1 PM at 15°E longitude and 2 PM at 30°E longitude. India is 5 ½ hours ahead of Greenwich.

What is great circle?

A great circle is a circle on the surface of a sphere with a radius equal to the sphere's radius and its center at the sphere's center. All pairs of opposite longitudes and the equator are great circles.

What are the characteristics of great circle?

(i) A great circle is a theoretical circle formed by the intersection of the earth's surface and an imaginary plane that passes through the centre of the earth and divides it into two equal parts.

(ii) All such circles must pass through or touch the centre of the circle.

(iii) Infinite number of circles that touch the two opposite ends of the sphere can be drawn on a sphere.

(iv) Intersecting great circles always bisect each other.

What are the uses of great circles?

Navigators use great circles to find the shortest distance between any two points on the earth's surface. A Great Circle Route is the shortest distance between two places on the earth and lies on the arc of a great circle. Using

Fig. 2.9. Great Circle Route

this hypothesis, the shortest route from New York to Moscow would be over the North Pole. Thus, it does not take into account restrictions such as weather or political restrictions imposed by the countries concerned. It also does not take into account, lack of landing and take off facilities for aeroplanes.

(ii) Great Circle routes are specially important for places that are on opposite sides of the globe. Most globes show great circle routes between distant ports across the Atlantic, the Pacific and the Indian Ocean.

(iii) Great circles are used by meteorologists to determine climate and weather conditions in a region.