GEOGRAPHY FORM ONE: Topic 5: MAP WORK

  Topic 5: MAP WORK

A map is a scaled representation the earth’s surface on a flat material. For example a piece of paper, wall, clothes and a piece of wood. Map reading is the process of examining the given topographical map, conventional symbols and signs Map interpretation is the process of examining a given topographical map of an area represented for the purpose of identifying the geographical information of an area.

 TYPES OF MAPS
The classification of maps is based on the purpose for which each map is drawn. Therefore map can be categorized into three types as follows:
 i) Sketch map
ii) Atlas map/ wall maps
iii) Topographical maps

 i) Sketch maps; A map drawn from observation (rather than from exact measurements) and representing the main features of an area.
 ii) Atlas map/ wall map; A collection of different maps that have been bound together in one volume to form a book. These maps are usually drawn to scales example shows town and cities, hills, mountains, valleys, forests, countries, etc.
iii) Topographical maps; Shows selected physical and human features in an area and their positions on the ground for example hills, village, mountains, lakes, ponds, rivers

COMPONENTS/ESSENTIALS OF A GOOD MAP
A map is good if it contains all the essentials of maps, therefore the essentials are good qualities of maps. The essentials of a good map are:
1) Key. Used to interpret symbols and signs found on a map. They appear in a box at one of the bottom corner of the map. 2) Title; Used to show what’s map is all about. This is the heading of the map. It can appear on top of the map or anywhere else
3) North direction; This is an indication of the north direction. It shows where north is and by knowing north one can know the direction and bearing of the place.
 4) Margin; This is a boundary or limit around the map. It gives or shows the reader and interpreter the end of the map.
5) Publisher and date publication; This shows when the map was produced and a publisher.
6) Latitude and Longitude / Grid reference. It used to locate the place on the map. For example the map of Tanzania is located at latitude 6°00' south of the equator and longitude 35°00' east of Greenwich meridian.
7) A scale; It shows the relationship between map distance and the actual ground distance for example 1cm to 10km means one centimeter on the map represents ten kilometers on the ground MAP SCALE Is the relationship or ratio between map distance and actual ground distance. Scale = Map distance Ground (actual) distance.

TYPES OF SCALE.
 We can classify the scale according to the size in our criteria. There are three types of scales;

a) Large scale.
They are used to present information on small areas for example a map of village buildings and farms. The map size involves all numbers less than 1:25000 I.e. 1:10000 and 1:5000 Characteristics of large scale.
 i) It has smaller numbers in the denominator.
ii) It shows features clearly
 iii) It contains geographical details.

b) Medium scale.
They are used to represent medium details shown on the map. i.e. 1:50,000 and 1:100,000. Example of a map that can be drawn using medium scale is a map of a district, region, city etc. c) Small scale. They are used to present information that is long. This type of scale covers a big area with less detail. For example a map of a country, continent or world. May involve numbers between 1 : 500,000 to 1 : 1000,000

Characteristics of small scale.
 i) It has the largest denominator.
ii) Contains a lot of geographical information.
iii) It does not show geographical features clearly.

WAYS USED TO EXPRESS MAP SCALE.
i) Statement scale. Refers to the scale which is expressed in terms of words or explanation. For example one centimeter on a map is equivalent to 10 centimeters on the ground.

ii) Linear scale Also is called plain or graphic scale. This is a line which is divided into two parts. The primary division and secondary division. The secondary are expressed in meters and placed on the left side from zero and primaries are expressed in kilometers and placed on the right side from zero.

iii) Representative fraction (RF) scale
Is written as a fraction or ratio eg. 1:50,000 50,000 The distance on a map is expressed as fraction of the actual distance on the ground. Therefore, RF scale = map distance Ground distance. The top number (numerator) represents the map distance on the ground and is usually more than 1. Scale conversion a) To change statement to R.F scale. 1cm represents 60km
  Soln
1km=100000cm 60km= x 1:6000000 Therefore R.F scale = 1:6000000 b) One centimeter represents 0.75km b) 1:250000 To convert into statement scale If 1km = 100000 cm ? = 250000 cm 100000cm. x = 250000 cm x 1km 100000 cm 100000 cm X = 1 4 Thus, 1 cm represents 0.25

IMPORTANCE OF SCALE ON THE MAP
a) Scale help to calculate area of a map
b) It enable us to calculate distance on a map
c) Scale shows the relationship between map distance and the actual ground distance d) Scale help us to enlarge and reduce the area on a map or the whole map
e) Scale can be used to calculate the vertical exaggeration on a map f) Scale is used to calculate the gradient on a map Question: Distinguish signs from symbols

QUANTITATIVE INFORMATION ON MAPS

A) MEASURING DISTANCE ON THE MAP
 Distance is the length of elongated features on the earth’s surface such as road, railway, river etc. How to measure distance. In order to obtain distance of any feature on the map, consideration should be made on whether the distance to be measured is straight or curved. Straight distance For all straight distances a ruler is used to obtain the distance directly from the topographical map given. Curved distance. It becomes difficult to obtain curved distance of the features by the use of a ruler directly from the topographical map when the area is inclined. In this case the following devices can be used:-

A. A pair of divider. A pair of divider is commonly used to measure the distance. You should start by breaking the length by using a pair of dividers then transfer some of the already drawn straight lines. Then transfer the measured line to the linear scale or ruler for calculation to get the actual distance.

B. A piece of a string. Slowly measures the distances by a piece of string along a given length then transfer it to a linear scale or ruler for actual calculation of the distance.

 C. A piece of strip paper Slowly lay a piece of paper along a given length then break your lengths into short segments then transfer to the linear scale for measuring and calculation. For example: The railway distance from station A to B was 20 cm, find ground distance in km if the scale used to construct a map is 1:50000 20 cm map distance Scale distance= map distance Actual distance Scale: 1:50000 If 1km = 100000 cm ? = 50,000 cm 100000 cm = 1km x 50,000 cm 100000 cm 100000 cm = ½ km = ½ km x 20cm =10km. The ground distance of railway from station A to B is 10 km

MEASURING AREAS ON A MAP/CALCULATE AREA OF REGULAR IRREGULAR
Area size refers to the bigness or smallness of an area on the earth’s surface i.e. the bigness or smallness of earth’s surface from topographical map consideration should be made whether the area is regular or not.
 E x e r c i s e 1)
To state the following.
 a) map
 b) map reading
c) Scale
 d) Contour
2) Why do we study maps?
3) State the ways of expressing scale.
 4) What is the importance of a scale?
 5) List at least 3 methods of calculating the linear distance of an object
6) The distance of the road is 16cm from Igurusi to Chimala, convert the distance in kilometers if the scale used is 1:100000 b) From the above convert the same distance in km if the scale is changed to 1:50000

REGULAR SHAPE These are areas with definite shapes such as squares, triangles etc. Their total perimeters or areas are obtained by mathematical formula i.e. length x width, side x side etc.

IRREGULAR SHAPE These are areas with indefinite shapes such as lakes, farms, ponds etc where these areas can be obtained by any of the following three methods; a) Square method b) Strip method c) Geometrical method

SQUARE METHOD
This is the most accurate and most widely method used. Square methods are normally used as follows;
a) Count all full squares that are complete
b) Count incomplete squares and divide them by 2 c) Add them with the full squares to obtain the total area in km2

METHODS USED TO SHOW OR LOCATE POSITIONS OF A PLACE ON A MAP.
 The following are major methods used to show positions of a place on a map.
 i) Grid reference.
ii) Place name
iii) Bearing and compass direction.
iv) Latitude and longitude. Place name. You can locate the position of a place by where the features are found i.e. Kigoma, Mbeya, Dodoma, Lindi etc. Grid reference. Grid reference is a network of vertical lines and horizontal lines on a map. Vertical lines whose numbers increases towards the east are called easting. Horizontal lines whose numbers increase towards the north is known as Northings. Where horizontal lines and vertical lines meet or cross each other they form a square known as grid square. (G.S). A grid reference point is written inform of six digits starting with three digits of Eastings then three digits of nothings. ·A ·C D· ·B 31 32 33 34 35 36 37 38 39 40 41 42 09 08 07 06 05 04 03 02 01 To write down the grid reference of point A, B, C, and D. A = 343086 B = 333036 C = 383077 D = 397046 NB: To write numbers of grid reference starts with easting then northing.

 LOCATION AND POSITION: COMPASS BEARING AND DIRECTION
 How to find direction of a place on map. Identify them due to points on the given map. Points may be given by using grid reference points, place name or letter. Draw a straight line connecting the two points Mark the major four cardinal points at the starting point with the word from. Now look at the question asked then provide your answer.
COMPASS BEARING.
Bearing are directions which measure degrees clockwise from north. They are written in three figures i.e. 0900 , 0450

HOW TO FIND BEARING ON THE MAP.
Identify the grid reference points given on the maps. Draw a straight line connecting the two points Draw the major four cardinal lines at the starting Now look at the question asked use a protector to measure degree clockwise from north up to the line joining the two points. Then Provide your answer in degrees BEARING. In bearing there is;
 a) Forward bearing
 b) Backward bearing

a) Forward bearing Is a bearing into a subject. Procedures to calculate forward bearing
 i. Identify the two points.
 ii. Join them with a straight lines
iii. Draw north direction on a second point.
iv. Measure the angle by using a protector.
v. State the bearing in terms of degrees of the direction.

b) Backward bearing. Is the opposite of forward bearing, it’s taken from the object to the observer while forward bearing is taken from observer to the object.
How to determine the back bearing.
i) Find forward bearing.
ii) Mark the cardinal point north direction of the opposite point
iii) Find the bearing of the observer along the straight line principally to determine the back bearing = FB + OR – 1800 BB= FB +1800 if FB < 1800 BB= FB -1800 if FB >1800 For example: The forward bearing (FB) of Tukuyu from Kyela is 0450 , Back bearing (BB) will be; BB = FB + or – 180. BB = 45 + 180 (FB added because it’s not greater than 180) Therefore Back bearing is 2250

 IMPORTANCE OF THE USE OF MAPS
a) People use them to reach their directions
b) Maps are used to describe the features of the earth
c) Builders are maps to plan the best use of the land
d) Road constructors use maps to construct new roads
e) Maps are useful in military activities f)Maps are used in conducting various geographical researches