PRIMARY SIX GEOGRAPHY ILBC Finding Location using Latitudes and Longitudes We have learnt about the basic elements of maps and how to measure What latitudes and longitudes are distances on maps. Let us now move How to locate places using latitudes on to locating places and features on and longitudes maps. On small-scale maps, this is done by using latitudes and longitudes. You will learn Fig 2.1 Note the latitudes and longitudes on this world map Latitudes Latitudes are actually imaginary horizontal lines running in an east-west direction around the Earth. They cannot be seen on the actual surface of the Earth. 15 ILBC PRIMARY SIX GEOGRAPHY The Equator is the 0˚ latitude which divides the Earth into halves: the upper half and the lower half. The upper half of the Earth from the Equator to the North Pole is called the Northern Hemisphere while the lower half from the Equator to the South Pole is called the Southern Hemisphere. Latitudes are measured in degrees and minutes from the Equator. In the Northern Hemisphere, the latitudes increase in value as they move northwards, that is, from 0˚ at the Equator to 90˚ N at the North Pole. Likewise, in the Southern Hemisphere, the latitudes increase in value as they go southwards, that is, from 0˚ at the Equator to 90˚ S at the South Pole. Fig.2.2 All lines of latitudes are given a number between 0˚ and 90˚, either North(N) or South(S) of the Equator Longitudes Longitudes are imaginary lines that run in a north-south direction from the North Pole to the South Pole on the Earth’s surface. They are measured in degrees and minutes east or west of the 0˚ longitude which is called the Prime Meridian or the Greenwich Meridian. It is called the Greenwich Meridian because it passes through a place called Greenwich, near London. 16 PRIMARY SIX GEOGRAPHY ILBC Check this out ! The words ‘latitude’ and ‘longitude’ have Latin origins. They mean ‘breadth’ and ‘length’ respectively. Fig. 2.3 The Greenwich Meridian divides the world into the Eastern and Western Hemisphere. Fig. 2.4 All lines of longitudes are given a number between Oº and 180º either East (E) or West (W) of the Greenwich Meridian Longitudes west of the Greenwich Meridian are measured from 0˚ at the Greenwich Meridian to 180˚ W. Likewise, longitudes that lie to the east of the Greenwich Meridian are measured from 0˚ to 180˚ E. Both the 180˚ W and 180˚ E are the same line of longitude. This line lies directly opposite the Greenwich Meridian and is known as the International Date Line. The International Date Line and the Greenwich Meridian divide the world into the Western Hemisphere and the Eastern Hemisphere. However, the International Date Line does not follow the 180˚ meridian along its entire course. Instead it bends at certain places to avoid cutting across any land (refer to Fig. 2.5). 17 PRIMARY SIX GEOGRAPHY Prime Meridian ILBC Fig. 2.5 The International Date Line and the Prime Meridian Use of Latitudes and Longitudes to Locate Places Latitudes and longitudes cross each other to form a network of lines or a grid. This grid makes it possible to state the exact location of any place on the Earth’s surface. Imagine you are on a ship sailing across the Pacific Ocean and your ship is sinking. To get help, you need to radio your location to another ship. If you are at latitude 30˚ north of the Fig . 2.6 Latitudes and longitudes form a global grid system Equator and longitude 10˚ east of the Prime Meridian, you would radio your position as 30˚ N10˚ E. Note that the latitude comes before the 18 longitude when describing a location. PRIMARY SIX GEOGRAPHY ILBC 30º N 20º N 10º N 0º 10ºW 0º 10ºE 20ºE 30ºE Fig. 2.7 The ‘sinking ship’ is located at 30 °N 10°E. Latitude An imaginary horizontal line that runs in an east-west direction around the Earth Longitude An imaginary vertical line that runs in a north-south direction on the Earth’s surface North Pole The northernmost point of the Earth Prime Meridian or Greenwich Meridian The 0˚ longitude South Pole The southernmost point of the Earth Recap Questions 1 What are latitudes and longitudes? 2 Why is the 0˚ longitude known as the Greenwich Meridian? 19 PRIMARY SIX GEOGRAPHY ILBC Finding using Location Grid References You will learn What grid lines, eastings, northings and grid references are How to locate places or features using four-figure references How to locate places or features using six-figure grid references Besides small-scale maps, we also use large-scale maps which show details of small areas of the Earth’s surface. Grid references are used to locate places and features on these maps. Eastings and Northings Examine the topographic maps shown in Fig 2.8 and Fig 2.9 on page 20 and 21. Notice the horizontal and vertical lines on them. These lines are called grid lines. Together they form a grid which divides the map into grid squares. Fig 2.8 An extract from the topographic map of Singapore The grid lines are numbered along the margins of the map. The vertical grid lines are called eastings because their numbers increase eastwards. The horizontal grid lines are called northings because their numbers increase northwards. A grid reference is a number 20 PRIMARY SIX GEOGRAPHY ILBC representing the point at which eastings crosses a northing. It is made up of the number for the northing. Using grid references, it is possible to describe the location of any place or feature on a map easily. Four-figure Grid References We use a four-figure grid reference to locate the grid square in which a feature is found. The following are the steps to take in finding a four-figure grid reference for a feature. (i) Locate a grid square where the feature is found. (ii) Read the easting (vertical lines) for the bottom left corner of the grid square. (iii) Read the northing (horizontal line) for the same left corner of the grid square. (iv) The four-figure grid reference for the feature is made up of both the northing. Northings (up the stars) 47 First, read the number of the line which runs down the left side of the square L 46 45 Second, read the number of the line which runs along the bottom of the square 44 43 42 16 17 18 19 Eastings (along the cooridor) 20 21 Fig 2.9 Can you identify the four- figure grid reference where the lake (L) is located? Using the steps described above, the fourfigure grid reference for lake (L) in fig 2.9 is 1845. 21 PRIMARY SIX GEOGRAPHY ILBC Check this out ! If you find it difficult to remember the order of the grid lines when citing a grid reference, try this: the letter ‘E’ comes before the letter ‘N’, so always code easting before northings. Six-figure Grid References You may have noticed that a four-figure grid reference only tells us the grid where the large feature is found. To find the exact location of a smaller feature such as a school or a post office, you will need to use the six-figure grid reference. As its name suggests, six-figure grid reference has six numbers instead of four. The following are the steps to take when finding a six-figure grid reference. (i) Locate a grid square on the map where the feature is. (ii) Divide the square into 10 equal parts along easting and the easting and northing. (iii) Number the parts from 0 to 9 along both the easting and northing. (iv) Estimate how far the feature is from the easting and the northing using the scale in tenths. (v) Write the value for the easting followed by the northing. 74 73 Fig. 2.10 locating the Police Station using a six-figure grid reference PS 72 71 22 04 05 06 07 PRIMARY SIX GEOGRAPHY ILBC Using the described steps above, the police station in Fig2.10 is located seven-tenths of the way between eastings 05 and 06. Hence, the easting is 057. The police station is also located two-tenth of the way between northing 72 and 73. Hence, the northing is 722. Therefore, the sixfigure grid reference for the police station is 057722. Eastings Vertical grid lines Grid A network of grid lines Grid Lines horizontal and vertical lines that run across a map Northings horizontal grid lines Recap Questions 1. What are grid lines? 2. What are eastings and northings? 3. What difficulty would you have in locating a place on a map which does not have grid lines? 4. List the steps needed to locate an area on a map. 5. List the steps needed to locate a specific place on a map. 23 PRIMARY SIX GEOGRAPHY ILBC Finding Direction You will learn Since the 11th century, sailors have used maps and compasses to help them find their way at sea. Today, we still use these to help us find our way around. A map helps us find out how to get to another place from where we are, and a compass helps us find direction. what cardinal points are how to tell direction using cardinal points what bearings are and how to use bearings to specify direction (only for students in the Special and Express streams) Cardinal Points Fig.2.11 Can you think of specific examples where a compass would be useful? Look at Fig.2.11. It shows a compass. There are four points marked on it: north, south, east and west. These points are known as the cardinal points. Four other points can also be seen on the compass. These additional points are marked north-east, south-east, south-west and north-west. Cardinal points can be used to show the direction of one place or a feature from another. So, a place or a feature may be described as being north, south, east or west of another. On maps, these cardinal points are shown by the directional indicator or compass rose. 24 Fig.2.12 The compass rose is a directional indicator that shows the cardinal directions north, south, east and west. PRIMARY SIX GEOGRAPHY ILBC Finding Direction Using Cardinal Points These are the steps to take when finding the direction of a place or feature (Y) from another (X). Refer to Fig.2.13 31 Y 30 29 28 27 X 03 04 05 06 07 Fig. 2.13 Finding direction using cardinal points (i) Draw a line joining the two places or features. (ii) At X, draw a vertical line that is parallel to the eastings of the map. This line indicates north. (iii) Look at X and use one of the cardinal points to describe the position of Y from X. From Fig 2.13, it can be seen that Y is northeast from X. Using the steps listed earlier, let us find the direction of BBC Birmingham Public Space from the Temple. (i) First locate BBC Birmingham Public Space and the Temple. (ii) Then draw a line from the centre of Temple to the centre of BBC Birmingham Public Space. . (iii) At the Temple, draw a vertical line that is parallel to the eastings of the map. This line indicates north. Hence, BBC Birmingham Public Space is to the south-west of the Temple. 25 PRIMARY SIX GEOGRAPHY ILBC The map below shows the Temple and BBC Birmingham Public Space. Fig.2.14 A street map of Birmingham Bearings Cardinal points are useful only for giving general directions. To be more exact, however, you should measure the direction in degrees. Directions, measured in degrees, are known as bearings. Bearings are measured from north or 0˚ in a clockwise direction. 90˚ coincides with the cardinal point east, 180˚ with south and 270˚ with west. Finding Direction Using Bearings To find the bearing of one place or feature from another on a map, we need to use a protractor. The following describes the steps to take. (i) To measure the bearing of B from A, draw a line to join the two points. (ii) Place the centre of the protractor at A. The 0˚ on the protractor must point to the north. (iii) The point on the outer edge of the protractor where the line joining A and B crosses shows the bearing of B from point A. Read the bearing off the protractor. (iv) You will see that the bearing of B from A is 135˚. 26 PRIMARY SIX GEOGRAPHY ILBC Measuring Bearing... Find the bearing of B from A Place your protractor over the north line with 0º at the top Give the answer as a three figure bearing A The bearing of B from A is 135º B Fig. 2.15 The bearing of B from A is 135º If the bearing is greater than 180˚, take the following steps. (i) To measure the bearing of X from A, draw a line to join the two points. (ii) Place the center of the protractor at A. The 180˚ of the protractor must be pointing to the north. (iii) Look carefully at the reading where the line joining A and X crosses the outer edge of the protractor. Note that this is not the bearing of X from point A. You have to add 180˚ to get the bearing of X from point A. (iv) In the diagram shown, the bearing of X from point A is 230˚, that is, 50˚ + 180˚. 27 PRIMARY SIX GEOGRAPHY ILBC Fig. 2.16 The bearing of X from A is 230º Bearings Compass directions which are measured in degrees Cardinal points Makings on the compass which indicate the directions north, east, south and west. 28 Recap Questions 1. What are the four main cardinal points? 2. Why is direction sometimes given as bearings?
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