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 researchesKupata notes za Geography click hapa
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