Latitudes and Longitudes

WEEK 5 &6

SUBJECT: GEOGRAPHY

CLASS: SS 1   

TOPIC: Latitudes and Longitudes

CONTENT: 

3. Meaning and uses of Latitude.
4. Equator 
5. Relationship with Major regions of the world (Tropics of Cancer and Capricorn, Arctic and Antarctic Circles
6. Latitude and distance.
7. Meaning and uses of Longitude
8. Great circle
9. Longitude and time.
10. Local Time, Standard Time and Time Zones.
11. International Date Line.
12. Difference and Similarities between longitude and latitude.

SUB-TOPIC 1: Meaning and Uses of Latitude

Meaning of Latitude. 

Latitude is an imaginary line drawn on the globe running from west to east. It is the angular distance of a point on the earth’s surface, measured in degrees from the centre of the earth. The earth is divided into equal halves – the northern and southern hemisphere by latitude (O0) called the equator. Other lines of latitude are parallel to the equator and to each other, hence, the latitude are also called parallels of latitude. 

Lines of Latitude run from west to east

The major lines of latitude are:

1. The Equator  (0°)
2. The Tropic of Cancer 23 ½ °N
3. The Tropic of Capricorn 23 ½ °S
4. The Arctic Circle 66 ½ °N
5. The Antarctic Circle 66 ½ °S

Equator: Equator is a line of latitude that divides the earth into two halves- northern hemisphere and southern hemisphere. It is 00. All other lines of latitude north or south take their readings from equator and they are parallel to it. It is also referred to as Great Circle. 

USES OF LINES OF LATITUDE

1. It is used in conjunction with longitude to locate places on the map.
2. It is used to calculate distance between two places on the earth’s surface. 

EVALUATION

1. Describe latitude.
2. State four major lines of latitude.
3. What is Equator?
4. State two uses of latitude.

Latitude is a measure of how far north or south of the equator a location is. The four major lines of latitude are the Prime Meridian, the Tropic of Cancer, the Tropic of Capricorn, and the International Date Line. The Equator is an imaginary line that divides the earth into two equal hemispheres, the Northern Hemisphere and the Southern Hemisphere. Latitude is used to calculate distances on maps and to predict the length of daylight at different times of the year.

Objective Questions .

1. What is latitude?

A. A measure of how far north or south of the equator a location is

B. A measure of how far east or west of the Prime Meridian a location is

C. An imaginary line that divides the earth into two equal hemispheres

2. What are the four major lines of latitude?

A. The Prime Meridian, the Tropic of Cancer, the Tropic of Capricorn, and the International Date Line

B. The Arctic Circle, the Antarctic Circle, the Tropic of Cancer, and the Tropic of Capricorn

C. The North Pole, the South Pole, the Equator, and the Prime Meridian

3. What is the Equator?

A. An imaginary line that divides the earth into two equal hemispheres

B. The Tropic of Cancer

C. The Tropic of Capricorn

4. What are two uses of latitude?

A. To calculate distances on maps and to predict the length of daylight at different times of the year

B. To calculate distances on maps and to predict the time of sunrise and sunset at different times of the year

C. To predict the weather and to calculate distances on maps

5. Which line of latitude is closest to the North Pole?

A. The Prime Meridian

B. The Tropic of Cancer

C. The Arctic Circle

6. Which line of latitude is closest to the South Pole?

A. The Tropic of Capricorn

B. The Antarctic Circle

C. The International Date Line

7. What is the difference between the Tropic of Cancer and the Tropic of Capricorn?

A. The Tropic of Cancer is north of the Equator and the Tropic of Capricorn is south of the Equator

B. The Tropic of Cancer is south of the Equator and the Tropic of Capricorn is north of the Equator

C. There is no difference between the two lines of latitude

8. What is the prime meridian?

A. An imaginary line that divides the earth into two equal hemispheres

B. The Tropic of Cancer

C. 0 degrees longitude

9. What is the international date line?

A. An imaginary line that divides the earth into two equal hemispheres

B. The line of longitude at 180 degrees east or west

C. The Prime Meridian

10. What is the difference between the Arctic Circle and the Antarctic Circle?

A. The Arctic Circle is north of the Equator and the Antarctic Circle is south of the Equator

B. The Arctic Circle is south of the Equator and the Antarctic Circle is north of the Equator

C. There is no difference between the two lines of latitude.

Interactive Questions and Answers

1. What is latitude?

2. What are the four major lines of latitude?

3. What is the Equator?

4. What are two uses of latitude?

5. Which line of latitude is closest to the North Pole?

6. Which line of latitude is closest to the South Pole?

7. What is the difference between the Tropic of Cancer and the Tropic of Capricorn?

8. What is the prime meridian?

9. What is the international date line?

10. What is the difference between the Arctic Circle and the Antarctic Circle?

Suggested Answers

1.Latitude is a measure of how far north or south of the equator a location is.

2.The four major lines of latitude are the Prime Meridian, the Tropic of Cancer, the Tropic of Capricorn, and the International Date Line.

3.The Equator is an imaginary line that divides the earth into two equal hemispheres, the Northern Hemisphere and the Southern Hemisphere.

4.Latitude is used to calculate distances on maps and to predict the length of daylight at different times of the year.

5.The Arctic Circle is the line of latitude closest to the North Pole.

6.The Antarctic Circle is the line of latitude closest to the South Pole.

7.The Tropic of Cancer is north of the Equator and the Tropic of Capricorn is south of the Equator.

8.The prime meridian is 0 degrees longitude.

9.The international date line is the line of longitude at 180 degrees east or west.

10.The Arctic Circle is north of the Equator and the Antarctic Circle is south of the Equator.

SUB-TOPIC 3: Latitude and Distance

Lines of latitude are used to calculate the distance between two places on the earth surface. To calculate distance the following procedure are to be followed

1. Locate the two places
2. Find the latitude difference between the two places involved. To do that, the formular used is
   1. North – North = subtract
   2. South – South = Subtract
   3. South – North = Add
   4. Equator (00) – North/South = Add or subtract
3. Multiply the latitude difference by 111km

Note that 10 of latitude is approximately 111km on land. This is derived by dividing the length of equatorial circumference (40,089km) by 3600 

i.e.  

EXAMPLE 1: Calculate the distance between the equator (Lat 00) and Egypt (300N)

Solution:

1. Locate the two places involved

Latitude of equator = 00

Latitude of Egypt = 300

1. The difference in latitude is 0 + 30 = 300
2. Since 10 =111km

Therefore, 300 = 30 x 111km = 3,330km

The distance between the equator and Egypt = 3,330km

EXAMPLE 2: Calculate the distance between South Africa (30os) and Spain (400N)

                      Solution:   

1. Locate the places involved

South Africa 300s

Spain 400N

1. Latitude difference 300 + 400 = 700
2. Since 10 = 111km

∴ 700 = 111 x 70 = 7,770km

The distance between South Africa and Spain is 7,770km

EVALUATION:

1. Calculate the distance between Point R (lat. 500S) and Point Q (lat. 350N)

SUB-TOPIC 1: Meaning and Uses of Longitude

Meaning of Longitude

Longitude is an imaginary line drawn on the globe (earth) running from north to south at right angle to the parallel. It is an angular distance measured in degrees east and west of the Greenwich meridian. All other lines of longitude are called meridian and are numbered in degrees east and west of longitude 00.

The longitude passing through London (Britain) and Accra (Ghana) is called Great, Prime or Greenwich Meridian and it is put at longitude 00. The major lines of longitude are showing in the diagram below.

Important Lines of Longitude

Uses of Lines of Longitude

1. They are used in calculating local time.
2. They are used in conjunction with latitude to locate places on the map.

GREAT CIRCLE

It is an imaginary circle on the earth’s surface with its plane passing through the centre of the earth, thereby dividing the globe into two hemispheres or two equal parts. Out of all the lines of latitude, only the equator is a great circle. Any two opposite longitudes (meridians) form a great circle. Thus, Greenwich meridian together with meridian 180° form a great circle. Likewise meridian 10°E and 170°W, 20°E and 160°W, and 50°E and 130°W all formed a great circle. The number of great circles is limitless or endless. Great circles can extend in any direction; east to west, north to south, north-east to south-west, and so on. Great circles are of equal length. The shortest distance between any two points on the earth’s surface is an arc of a GREAT CIRCLE.                                                                            A great circle route is therefore, the shortest route between two points on the globe. 

Modern aircraft follow routes along sections of great circles to save time and fuel. But it is not always possible to follow great circle routes because of:

1. political reasons if some countries forbid the use of their air space,
2. the fact that air routes tend to follow the land in case of accident and rarely fly for long distances over the sea,

III. the fact that aircraft may have to call at several airports which are not on a straight line.

Evaluation:

1. Define longitude.
2. Mention three major lines of longitude.
3. What is Greenwich meridian?
4. State two uses of lines of longitude.

SUB-TOPIC 4: Differences and Similarities between Lines of Latitude and Longitude

SIMILARITIES BETWEEN THE LINES OF LATITUDE AND LONGITUDE.

1. Both are imaginary lines drawn on the earth’s surface.
2. Both are angular distances of a point on the earth’s surface.
3. Both are measured in degrees.
4. Both are used to locate places on the earth’s surface.
5. Both contain great circle.

DIFFERENCES BETWEEN THE LINES OF LATITUDE AND LONGITUDE.

1. Lines of latitude are called parallels while lines of longitude are called meridians.
2. Parallels are drawn from west to east while meridians are drawn from north to south.
3. Distance between two meridians decreases towards the poles while for the parallels the distance is constant.
4. Parallels have different circumference while meridians have equal circumference,
5. Parallels never meet while meridians meet at the poles.
6. Parallels are marked 0° to 90° north and south of the equator while meridians are marked 0° to 180° east and west of the Greenwich.
7. Of all the parallels only the equator is a great circle while all meridians form part of a great circle.
8. The Greenwich is a reference point of all the meridians while the equator is a point of reference of all the parallels.
9. Parallels are used to calculate distance while meridians are used to calculate time.
10. The most significant parallels are 0° (equator), 231/2°N (Tropic of Cancer), 231/2°S (Tropic of Capricorn), 661/2°N (Arctic Circle), 661/2°S (Antarctic Circle), 900N (North Pole) and 900S (South Pole) while those of meridians are 0° (Greenwich Meridian) and 180° (International Date Line). 

EVALUATION:

1. Differentiate between latitude and longitude
2. Mention four similarities between longitude and latitude.

SUB-TOPIC 5: Time and Time zone

Local Time

The situation in which time varies for every degree of longitude is what is referred to as local time. This means that each meridian has its own local time. Therefore, as soon as longitude changes, time changes as well. Thus, if time is 12noon at Lagos longitude 3°E, it will be 12.04 p.m. at Ibadan longitude 4°E. If each town were to keep the time of its own meridian, there would be much difference in local time between one town and the other and great confusion would have set in because of the variation in local time from place to place.

To avoid this confusion, a system of standard time is observed by all countries.

Longitude is used in calculating local time. To do so, the following procedures are to be followed

1. Locate the places involved in question
2. Find the longitude difference 
3. Convert the longitude difference to time
4. Adjust the time according to the direction of the movement (West or East)

EXAMPLE 1: What will be the local time in Nigeria (Long 150E) when it is 5.00pm in Ethiopia (Long 450E)?

SOLUTIONS

Longitude difference. To find the longitude difference the formula used is 

1. East – East = Subtract
2. West – West = Subtract
3. East – West = Add
4. Greenwich Meridian (00) – West or East = Add or Subtract

Longitude difference = 450 – 150 = 300

Convert the longitude difference to time

The formula used is

3600 = 24hrs

150 = 1hour

10 = 4minutes

Using 150 = 1hour

∴300 =

OR

Using 10 = 4minutes

300 =

To adjust the time, subtract 2hours from 5.00pm for the direction of arrow

5.00pm – 2hrs = 3.00pm

Therefore, the local time in Nigeria is 3.00pm. 

Note that if the direction is to the west, you subtract the calculated time from the given one. But if direction of arrow is to the east, the calculated time will be added to the given time.

CALCULATION OF LONGITUDE

PROCEDURE

1. Locate the places involved
2. Find the time difference
3. Convert the time difference to longitude
4. Adjust the longitude to the direction of movement (west or east)

EXAMPLE: What is the longitude of a town X whose time is 12.00noon when Greenwich Mean Time is 6.00pm?

SOLUTION:

Procedure A: 

Note: Town X has to come first because you get 12noon before 6.pm

Procedure B: Find the time difference 

                                               12.00pm – 6.00pm = 6hrs

Procedure C: Convert 6hrs to longitude. 

Since 150 = 1hour

∴6hrs = 6 x 150 = 900

Procedure D: Since the arrow is pointing to the question mark (i.e. west), therefore, the 900 is to the west which is 900W. Therefore the longitude of town X = 900W.

Standard Time and World Time Zone

This is a time generally adopted by a country in order to eliminate differences in local time between one town and the other within the same country. It is usually taken in reference to the Greenwich meridian. For example, Nigeria regulates its time with longitude 150 E, which is an hour ahead GMT.

The world is divided into 24 standard time zones, each of which differs from the next zone by 150 in longitude or one hour in time. Some bigger countries like Canada, USA, etc adopted many time zones due to the area extent of the country. For example, Russia and China are divided into eleven time zones while both Canada and USA have five time zones. 

Greenwich Mean Time (GMT)

This is also called world time and it is longitude 00.All countries of the world take or adjust their time from longitude 00. Countries locate on longitude 00 such as Accra (Ghana), London (Britain), Paris (France), Algiers (Algeria), etc. observe GMT. Nigeria for instance is on longitude 150 E which is an hour ahead of Ghana.

EVALUATION:

1. What will be the local time at Fuji Island longitude 1780 E when it is 1.00pm at Greenwich on Monday 4th of December 1959?
2. Write short notes on the following: (i) standard time (ii) Greenwich meridian (iii) local time. 
3. A football match is to be played on Saturday in New Zealand (1500E) between the host country and Nigeria (150 E). If the match is to be televised live, at what time should Nigerians tune in their television to watch the kick-off scheduled for 4.00pm in New Zealand (WASSCE June, 2001). 

Sub – Topic 6: International Dateline and Grid references

This is an imaginary line running from north to south through Pacific Ocean. The line is zig-zag in some places to avoid some island group thereby removing the confusion of dividing one island into different date.

Where this line is crossed, the date changes by exactly one day (24hours). When crossing IDL (Longitude 1800) from west to east 24hours is gained. If it is crossed from east to west 24hours is lost. For example, if a traveller crosses IDL on Friday 13th to the east, the day becomes Thursday 12th, while crossing it to the west on Friday 13th, the day becomes Saturday 14th.

International Date Line

EVALUATION:

1. Explain in detail the International Date Line.

GENERAL EVALUATION:

1. Distinguish between Standard time and Greenwich Mean Time ( SSCE NOV.,1992)
2. If the  GMT is 10.00am, 5th July, when the local time in a place X is 4.48am, 4th July, find the longitude of place X              (SSCE NOV.,1992)
3. Write notes on each of the following: (i) Great circle (ii) World Time Zone (iii) Small circle.
4. Explain four ways in which lines of Latitude differ from lines of Longitude. (SSCE June 1993)
5. Distinguish between Meridian and Parallel ( WASSCE June, 2001)

WEEKEND ASSIGNMENT

Objective Tests: Choose the correct answer from letter A-D

1. The longitude that joins Longitude 180° at the opposite side of the globe to form a Great Circle is (A) Longitude 0° (B) Longitude 30°E (C) Longitude 150°W (D) Longitude 170°W.
2. What is the distance along a great circle between Latitudes 270S and 23.50N of the equator? (A) 5,705.5km (B) 5,610.5km (C) 5,500.5km (D) 5,405.5km.
3. The angular distance of a point on the Earth’s surface measured in degrees from the centre of the Earth east or west of the Greenwich Meridian is known as (A) axis (B) latitude (C) orbit (D) longitude.
4. The degree of longitude through which the Earth spins within 3 hours is (A) 150. (B) 300.                 (C) 450. (D) 600.
5. Which of the following countries is located on longitude 00?  (a) Nigeria (b) Gambia                          (c) Ethiopia (d) France

Essay Questions:

1. Distinguish between Local time and Standard time.