MAP READING AND INTERPRITATION NOTES

 

SOCIAL AWARENESS ORGANIZATION (SAO)

EXTRA STUDIES DEPARTMENT

K/SAMAKI MKUNAZI WA KWANZA – ZANZIBAR

P. O. Box: 814, E – mail: Saoznz@gmail.com

PREPARATION FOR CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

(FORM 3 & 4)

M A P

READING AND INTERPRITATION

LESSON NOTES

PREAPERD BY GEOGRAPHY TEACHER

PROF. KHALID

MOBILE NO: +255 774 457171 OR +255 678 571813

EMAIL: khazab77@gmail.com

SAO EXTRA STUDIES DEPARTMENT

(GEOGRAPHY UNIT)

MR. KHALID USSI KHAMIS, He was educated at various schools and institution. These include

§   Kisiwandui Primary School (2000 – 2006)

§   Hailesellasie Secondary School (2007 – 2008)

§   Kiembesamaki Secondary School (2008 – 2014)

§   The State University of Zanzibar (2015 – up to now)

He was also employed as per time and part A – level and O – level Geography teacher at different school. These include

§   Kiembesamaki Secondary School

§   Alharamyn International School

Prepared by,

…………………………………..

PROF. KHALID USSI KHAMIS

BAED – SUZA, 2015

PROF. KHALID 2015

0774 457171

Second print 2016

ACKNOWLEDGMENTS

I wish to thanks Allah for give me a great ability to prepare this pamphlet of map reading and interpretation which one way or another can help the form 3 and form 4 students in their national examination.  Also I wish to thanks may dear teacher Mr. IDDI ALI MOH’D, Geography teacher, Kiembesamaki High School for his great contribution that made me to be very effective in the preparation of this pamphlet, without forget my another Geography Teacher Mr. Khamis Fadhil of Summait University for give me his contribution. I wish to thanks another Geography teacher Mr. Omar Mwinyiussi Malik of Kiembesamaki Secondary School for his contribution. Also I wish to thanks all Social Awareness Organization members and all those who in one way or another kindly contributed morally or materially in all processes in production of this pamphlet.

PREFACE

I have a great pleasure in presenting to my readers, students and teacher alike this first edition of Map reading and interpretation pamphlet.

This pamphlet planned to CSSE part of map reading in depth, gains its delightfully fresh approach by combining a fluid and vivid text with an amusing and highly original style of narration. It is hoped that it will be found to be great help to all.

I am confident that this thoroughly revised and enlarged edition will find even more welcome reception. Suggestions for the improvement of the pamphlet are mostly welcome through face to face, through cell phone 0774 457171.

MAP READING AND MAP INTERPRITATION

What is a map?

A map is a scaled representation of part or whole of the earth surface on a flat body such as piece of paper, black board, wood or cloth. Those a map must be drawn to scale.

Map readings a systematic identification of natural features and manmade features. Natural features include mountains, plateaus, hills, valleys, river, ocean, rocks, plain etc. and manmade features include roads, railway, buildings, dam etc.

TYPES OF MAP

There are many types of map according to purpose and function but the main types of map are only two. These are topographical map and statistical map.

1.      TOPOGRAPHICAL MAP:

The maps are named with the word “topography” which has been derived from the Greek word of “Topos”. The word topos means the actual appearance of place by its natural and artificial features. Thus; topographical map is defined as the one which show the actual appearance of an area represented by giving out general land details of both natural and artificial features. Natural features include river, mountain, plateau, hill and artificial features include road, railway, building etc.

CHARACTERISTICS OF TOPOGAPHICAL MAP

(a)    Show both natural and artificial features of the area represented

(b)    They are drawn on either medium or large scale depending on the size of the area represented.

(c)    Represent small or limited parts of a country

(d)    They are more detailed as represent small parts on large scale

CONTENTS OF TOPOGRAPHICAL MAP

Any topographical map shows three kinds of contents. These are natural contents, artificial contents and supportive content.

(i)        Natural contents: This is all features that are distinctive from manmade features like mountain, plateaus, rivers, ocean, Lake Etc.

(ii)      Artificial contents: This includes all man made features such as road, railways, settlement, airdrome etc.

(iii)     Supportive contents: These are the map’s marginal information give to assist the reader of the map. Some of the supportive contents include title, scale, north direction, key etc.

FACTORS THAT DETERMINE THE CONTENTS OF

TOPOGRAPHICAL MAP

(a)    Purpose of a map: This largely depends on the aim of cartographer. Usually maps are selective in a sense that not all land information can be shown on the maps. Aim of the cartographer determines what to be shown on a map.

(b)    Scale size of a map: Maps are to different scale sizes depending on the size of the land to be represented. it has to be noted that scale size of a map is about contents to be shown on a map. thus if there are two maps of the same area of land but drawn by the different scales sizes they are likely to differ in contents

(c)    Date of compilation: Date of compilation refers to a period of time at which a map was published/produced. It has to note that land information is dynamic overtime. Due to this fact map is likely to show information, which was represent by the time when it was prepared. hence maps drawn at different periods of time are likely to differ in terms of contents

(d)    Nature of the land represented: A map shows what is found at a place and otherwise therefore maps of different places are likely to differ in terms of the contents

(e)    The nationality of the cartographer: The map of a place can be drawn by the foreigner or indigenous cartographer. Hence the two maps are likely to differ in contents due to the fact that the foreigner cartographer might not include same contents because of being not familiar with the area.

2.      STATISTICAL MAP

There are the maps, which show distribution of different aspects such as temperature, rainfall, settlement, vegetation etc. They are for example Dot maps, Isoline maps, Flow line maps etc. statistical maps are differently named depending on the means of showing distribution on a map face.

MARGINAL INFORMATION/ COMPONENTS OF A MAP

This is the information shown on a map to enable the reading and interpretation of the geographical information of an area represents. This include:-

(a)    Title: Is the heading of the given map. The significance of the title is to tell what the map is all about.

(b)    Key: Is the list of all convectional symbols and sign shown on the map with their interpretation.

(c)    Scale: is the ratio between the distance on the map and the actual ground distance. Scales enable the map user to interpret the ground measurement like roads distance, area sizes, gradient etc.

(d)    Indication of north direction: Is the indication or indicated with the north direction used to know the other important direction of the mapped area like east, west, south, west etc.

(e)    Margin: Is the frame of the map. It is important for showing the end of the mapped area.

(f)       Sheet number: Is the reference number indicated on top of map provided used to given the number of the map provided.

(g)    Date of compilation: It is a date of map publication. It is very important for a date of compilation to appear on a map. This enable map user to realize whether the map is updated or outdated or any change which occurred in the area.

MAP SCALES

A scale is a ratio or proportion of the distance on a map to a corresponding distance on the ground or scale is a relationship between the distance on the map and the actual ground distance.

Accurately drawn maps should show exact proportionality between the distance on the ground and those on the map.

TYPES OF SCALES ON A MAP

Scales are classified according to the method used in classifying them. There are two major ways of classifying scale:

(a)    On the basis of the way their sizes.

(b)    On the basis of the way they are expressed.

CLASSIFICATION OF SCALES ACCORDING TO THEIR SIZES

Scales of this type are classified into three.

(a)    Small scales

(b)    Medium scales

(c)    Large scales

(a)  SMALL SCALE MAP

In these types of map, map distance is represented by small measurement on ground. It covers wide area and show only large towns. Features are greatly reduced and appear very small. The maps show few contents due to the limitation of the map space. The map scale range from 1:250,000 to 1:1000, 000.

(b)  MEDIUM SCALE MAP

These maps represent areas, which are neither too large nor small example villages, districts or town. The features on the ground are relatively reduced and map show moderates contents. The map scale range from 1:50,000 to 1:250,000.

(c)  LARGE SCALE MAP

These are used when drawing small area such as village, school, streets etc. One unit on the map represents very few units on actual ground distance. They are used to represents small ground areas. The map content is enlarged and they are clearly seen. The map scale range from 1:5000 to 1:25000.

CLASSIFICATION OF SCALES ON THE BASIS OF THE WAY THEY ARE EXPRESSED

Scales can be classified according to how they are expressed. Under this classification, there are three types of scales.

(a)    Statements scale

(b)    Representative Fraction (RF) scale.

(c)    Linear (graphic) scale.

(a) STATEMENT SCALE

A statement scale is expressed in form of a written statement, e.g. one centimeter on the map represents ten kilometer on the ground. This can also be expressed in short as 1cm represents 10km or 1cm to 10km.

A statement scale is simple to express. However, it may be difficult for users who are not familiar with the unit of measurement used in the scale. If the map is reduced or enlarged, the scale will not remain the same.

(b) REPRESENTATIVES FRACTION (RF) SCALES

A representative’s fraction scale is written as a fraction (e.g. ¹/_50,000) or ratio (e.g. 1: 50, 000). The distance on the map is expressed as a fraction of the actual distance on the ground. This means that any distance on the map represents ¹/_50,000 of the actual distance on the ground.

Therefore, R.F. scale = Map distance

                                         Ground distance

(c) LINEAR (GRAPHIC) SCALES

A linear or graphic scale is expressed as a short or long line subdivides into smaller equal units. There are two kinds of linear scales: the short line scale and the long line scale.

A short line scale comprises a single short line that represents the actual ground distance. To get the unit of measurement on the map, one has to measure the length of the line in centimeter.

                  0                            1km

A long line consists of a long line that is divided into several equal parts. It has two sections.

·      The right hand side of the zero point which is referred to as the primary section.

·      The unit on the left hand side of the zero point which is subdivided into fractions and it’s referred to as the secondary section.

                Primary section                                                   secondary section

Linear scale are expressed graphically, they show the specific units of measurement, they provide a direct measure of the distance on the corresponding distance on the map. This scale has the advantage of remaining the some even after the map is reduced or enlarged

SCALE CONVERSION

Scale conversion is a cartographic process of changing map scale from one form of expression into another. The cases may include the following:-

(a)    Conversion of Representatives scales into statement scale.

Example

Given a Representatives fraction scale of 1:50,000 convert it into a statement scale

Solution

We already know that 100000cm make 1km, there fore

1km         =          100,000cm

?              =          50,000cm

1km         X       ¹50,000cm       = 1  km  =  0.5km

²100, 000cm                    2

Therefore 1cm represents 0.5km.

(b)    Conversion of statement scale into representative’s scale.

Example

Given that a statement scale of 1cm represents 0.5km, convert it into representative’s fraction (RF) scale

Solution

We already know that 100000cm make 1km, there fore

1km         =          100,000cm

0.5km     =                 ?

0.5km     X          100,000cm   = 50,000cm

   1km

Therefore 1:50,000      or        ¹/_50,000

(c)    Conversion of statement scale into linear (graphic) scale.

Example

Given that a statement scale of 1cm represents 0.5km, convert it into linear (graphic) scale.

Solution

1cm        =          0.5km

  ?            =          1km

1cm        X          1km    = 2cm

         0.5km

Let your line is 5km

2cm        =          1km

?              =          5km

2cm        X          5km    = 10cm, this is the length of your line

         1km

(d)       Conversion of linear (graphic) scale into statement scale

Example

Given that .

Convert into statement scale

Solution

2cm       =          1km

           2                        2

         1cm       =          0.5km

Therefore 1cm represents 0.5km

IMPORTANCE OF MAP SCALES

Scale is useful in two varied ways of map reading and interpretation, and map making.

In map reading and interpretation

(a)       Enables the map users to understand the relationship of distance between the map and the actual ground represented.

(b)       It is useful in understanding the relative size of the area mapped by considering the used scale size.

(c)       It is very useful in making area size, distance and gradient determination of the geographical features which appear on a map and up on the actual area.

(d)       It is useful to judge the amount of the details of an area represented by taking into consideration of the scale size used.

(e)       Scale is used to show the relationship between the map distance and the ground distance.

In map making

(a)       Determines the size of the map to be constructed.

(b)       Control the amount of details to appear on the map relatively to the scale size used.

(c)       It is very useful in the cartographic process of map reduction and enlargement.

(d)       Controls the size of the convectional symbol, signs and abbreviation.

(e)       It is useful in making map projection.

(f)          Controls or determines the size of the ground to be mapped.

THE VALUE OF GEOGRAPHICAL MAP

(a)       Provide the basis for making geographical details of regions represented. I.e. the geographical facts of an area such relief, drainage, settlement etc.

(b)       Maps are so power full tools for making spatial analysis of geographical facts of areas represented.

(c)       They are so potential for field studies such as military, aircraft, agriculture etc.

(d)       Maps are useful for giving position location of geographical features by varied methods of grid reference, place naming etc.

(e)       Maps are very useful for traveling purpose. They guide people to reach their destination.

(f)          Maps are used on various projects like land use planning, population census etc.

(g)       Map make storage of the geographical data of areas represented.

(h)       Maps are potentially used to asses’ reliable measurements of the geographical features. The measurements can be of area size, distance etc.

(i)           Maps enable us to the distribution of different statistical data on the earth surface.

DISTANCE AND AREA SIZE MEASUREMENTS

Topographical maps are potentially used to assess the measurements of the geographical features observed on maps with reflection to the actual areas represented. It is therefore important to learn how the measurements of the geographical features of presented areas can be established from the topographical maps.

The popular ground measurements which can be established from the topographical maps are of distance and area size of different land structures.

DISTANCE DETERMINATION ON A MAP

Distance is defined as the length of an elongated feature between the two points on the earth surface expressed in unit of linear measurement like meters, kilometer and miles

Distance measurement of any elongated object on the topographical map has to take into consideration of key issues like map scale and the appearance of the elongated objects on the topographical map given whose distance is to be measured

Distance measurements of straight elongated objects

For a straight elongated object or features, one has to use a ruler more directly to get the convectional distance of the object on the map. I.e. a ruler has to be placed along the elongated object to be measured. The convectional distance is define which measured directly from the map i.e. map distance

Distance measurements of the curved elongated objects.

It becomes difficult to obtain the convectional distance of the elongated feature by use of a ruler directly from the topographical map when the distance to be measured is not straight. With these challenges and others, one has to devote the use of the following tools to get the convectional distance of what required to be measured. The tools include the following.

In this case, the following devices are used:-

(a)    A pair of divider:  a pair of divider is commonly used to measure short distance.

(i)     Break the length into short segments by a pair of divider.

(ii)   Transfer the segments to already drawn straight line.

(iii)  Then transfer the line to the linear scale or ruler for calculation to get actual distance.

(b)    A piece of string or thread: Slowly lay a piece of string or thread along a giving length. Then transfer the string or thread to the linear scale or ruler for calculation to get actual distance.

(c)    A piece of strip paper: Slowly lay a strip paper along a given length, and then break your length into short segment. Then transfer it to the linear scale or ruler for calculation to get the actual distance.

Example:

Calculate the length of road from grid reference 123433 to grid reference 6786765. Give your answer in km.

Solution

The map distance of road from grid reference 123433 to grid reference 6786765 is 23.5cm

According to map scale 1:50,000

1km         =          100,000cm

?              =          50,000cm

1km         X       ¹50,000cm       = 1  km  =  0.5km

²100, 000cm                2

Therefore 1cm represents 0.5km.

    If    1cm     =          0.5km

 23.5cm =             ?

23.5cm   X         0.5km  = 11.75km

             1cm

Therefore the distance of road from grid reference 123433 to grid reference 6786765 is 11.75km

AREAS SIZE DETERMINATION

Area sizes refers to the biggest or smallness of an area on the earth’s surface, e.g. the bigness or smallness of water body, plantation etc. To determine the size of the area on the earth’s surface from topographical map, consideration should be made on whether the area is regular or irregular.

Area size determination of anything from the topographical map should take into consideration of key issues like map scale and the shape of the features on the topographical map given whose area size is to be measured whether regular or irregular.

AREAS SIZE DETERMINATION FOR REGULAR FEATURES

Regular features are the ones whose shape well defined. They include square, triangle, rectangle, circle and others of the same reflection. To calculate the size of this regular figure, someone has to apply a relevant mathematical application with respect to the shape of the features observed on the topographical map.

(a)    Area of square: In order to find the area of square, there should be measurer the length (L) both side and convert into ground distance by using the map scale provided then multiply the two measurement. The formula to be used is Area = L²

 

                                                                                    4cm

                                                                         

(b)       Area of triangle: To find the area of triangles there should be measure the length of the base and the length of the height then convert into ground distance by using map scale provided.

 The formula to be used is Area = ½ X Height X Base

 

                                  H                                                                                                                                                                                                                                                                                                                                     B

(c)      

Area of rectangles: In order to calculate this area, it should be measure the length of base and width and convert into ground distance. The formula to be used is Area = Base X Height

              

                       H

                                                               B

AREA SIZE DETERMINATION FOR IRREGULAR FEAGURES

These are areas with indefinite shapes such as lakes, farms, ponds etc. Where the areas can be obtained by any of the following three methods which are square/grid methods, stripping method and division/composite method

(a)    Square or grid method: This is the most accurate and most widely used method. Grid reference square is normally used.

(i)     Count all complete/full squares.

(ii)   Count all incomplete squares and divide by two.

(iii)  Add them with the full squares to obtain total area in km²

Example: Calculate the area covered by forest below. Give your answer in km²

Solution

Complete square       = 1 square

Incomplete square    = 10 squares

Area       = Complete square   +    Incomplete square

                                                                               2

Area       = 1square     +     10 squares

                                                        2

Area       = 1 square    +     5 squares

Area       = 6 squares.

According to map scale 1:50,000

1km   X   1km    =    1km²

2cm        =          1km

1sq          =          1km²

6sq          =            ?

6sq          X          1km²   =   6km²

            1sq

Therefore the total area covered by forest is 6km²

(b)    Strip or division method: This is less accurate method. It’s normally used when the map has no grid lines on its face.

(i)     Divide the area given in strips of equal width.

(ii)   Find the area of each strip by the formula length X width.

(iii)  Add them together to get total area in km²

(c)    Geometrical or composite method: This method involves simple geometrical figures drawn in a given map e.g. squares, rectangles, triangle etc. Find area of each figure and then add them together to obtain total are in km²

MEASURING BEARING AND DIRECTION ON A MAP

BEARING

The method is mostly used to establish the location of a place from another place by giving the degree angle measured clockwise from north.

Bearing is the degree angle of an observation the line connecting two points on the map with reflection to an area on the earth’s surface measured clockwise from north direction.

PROCEDURES FOR BEARING DETERMINATION

(a)    Identify the two recommended points on the map by considering the grid reference or place names given. Sometimes both grid reference and place names can be provided together.

(b)    A straight line has to be drawn to join the end points on the map. The line represents an observation sight between the two places in a mapped area on the earth’s surface represented.

(c)    Establish the four cardinal points at the point of observer. The establishment of the cardinal points should take into consideration of the north direction indicated on the map.

(d)    Take the protector and measure the angle of an observation line that connects the two points clockwise from north direction.

(e)    Read the angle in three numbers. Example 090⁰

EXAMPLE

Determine the bearing of point B from point A

                                                                 N                   B

                                                                   45

 

                                                                   A

The bearing of point B from point A is of about 045

BACKWARDS BEARING

It is the reverse of the bearing of an object measured in front of the observer’s position. The bearing of an object measured clockwise from north direction in front of the observer’s position along the observation line is called forward bearing while the bearing of an object measured clockwise from north direction backwards to the former observer’s position along the same sight line is called backward bearing

Backwards bearing of objects is obtained by measuring the degree angle of an observation line clockwise from north direction backwards to former observers’ position.

NOTE 1

If the forward bearing of the object has been established, the backwards bearing can be determined by mathematical procedure

BB   = FB+/- 1800

 

BB = FB + 180⁰ if less than 180⁰

BB = FB – 180⁰ if the FB is greater than 180⁰

DIRECTIONS

A direction means the course or a line along which a person or thing moves or looks or which must be taken to reach a destination.

Direction on the map can be given in four, eight or sixteen cardinal points of compass and their corresponding bearings.

NOTE 2

The procedures of finding the direction are the same to those procedures of finding the bearing, instead of write the number of angle (bearing), here we write only direction such as North, South, West etc. of a given point.

DRAWING CROSS – SECTION ON A MAP

A cross – section is a dramatic representation of the relief based on heights shown by contours on a map extract. The cross – section shows the general appearance of the land surface between two identified points. It shows the general appearance of the land surface between two identified points. It shows hills, plains, lowlands, escarpments, depressions, etc. It is alternatively known as relief section or relief cross profile or topographical profile.

On the cross – section, both natural and human features like river, road, railway, vegetation may be marked and named.

Cross – sections are of two types and include the simple (sketch) or relief cross profile and annotated cross sections

(a)       Simple or relief-cross profile: Is the one not drawn to scale and is made to show the general appearance of the landscape between the given points in terms of relief. This type of cross section show few details.

(b)       The annotated cross section: Is the one drawn to scale and which the position of important places and features indicated more accurately. It is also known as accurate cross section which means cross section which show more details.

THE SIGNIFICANCE OF CROSS SECTION

(a)       Provide a clear pictorial view on the structural appearance of area in between of the two places. With respect to this, a person may easily determine types of slope in the area and the appearance of the area.

(b)       It is useful for intervisibility determination between two points in the area. This is made possible as a cross section shows physical appearance of an area and if clearly observed the judgment of intervisibility become easier.

(c)       It shows clearly the altitudes of the different parts of the landscape in between of the two points in the area.

(d)       Cross section aid to make gradient determination of the sloped landscape by relating VI and HE

CONSTRUCTION OF CROSS SECTION

The construction of cross section should fundamentally follow the following significant procedures or steps:-

(a)       Identify and mark the two end points to be sketched on the topographical map. The point can be identified by taking into consideration of the grid references.

(b)       Draw the straight line with the use of ruler on the map to join the two point identified.

(c)       Take a piece of paper with a straight edge or fold it to get straight edge and place along the drawn straight line on the map. The piece of paper has to be slightly longer than the length of the line joining two end points. On the piece of paper mark the following important details

·      The two end points, which have been identified on the map

·      Where every contour line cuts the line

·      The contour heights

·      The important landscape features of both natural and manmade feature

(d)       Find the appropriate vertical and horizontal scales. The vertical scale is computed as follows

Vertical scale           =          highest altitude – Lowest altitude

                                                                          Graph space

(e)        Construct the frame work for drawing the cross section. The frame work should have both vertical and horizontal line distances.

(f)           Take a piece of paper, which has been marked with the map details for cross section, and place along the horizontal line distance of the framework.

(g)        Connect the plotted points with pencil using the free hand to develop the structural appearance of the landscape.

(h)         Finish the cross section by including the following

·      Heading to show what the cross section is for about.

·      Natural and manmade features which show the clear outlay of what represented by the cross section

·      Vertical scale; this show the relationship of altitudes between the cross section and the actual ground represented.

·      Horizontal scale; this shows the relationship of horizontal distance between the cross section and landscape represented.

Cross section from point a to b

VERTICAL EXAGGERATION

A cross section by its nature has both vertical and horizontal scales. The vertical scale is nearly always magnified, while the horizontal scale is steadily constant. The amount of magnification of the vertical scale over horizontal scale is known as vertical exaggeration.

Vertical exaggeration is thus, defined as the amount of times by which the vertical scale is larger over horizontal scale or the relationship between the vertical scale to horizontal scale

Vertical exaggeration is very important in cross section drawing as it determine the shape of the features represented on the cross section

The standard vertical exaggeration of the cross section drawn from most of the topographical map with scale of 1:50,000.

Vertical exaggeration is principally determined by applying either one of the following two principle formula

Vertical exaggeration      =          Denominator of HS

                                                            Denominator of VS

OR

Vertical exaggeration      =          Vertical scale (VS)

                                                            Horizontal scale (HS)

EXAMPLE

If a cross section has the horizontal scale of 1:50,000 and vertical scale of 1:10,000, whose vertical exaggeration is determined as follows

Vertical exaggeration      =          Vertical scale (VS)

                                                            Horizontal scale (HS)

                                                =          50,000

                                                            10,000

                                                =          5

Thus, the VE = 5. This implies the vertical scale is larger for 5 times to horizontal scale.

INTERVISIBILITY

Intervisibility is the act of telling whether the two points or places in the area as observed on the map intervisible or not

A good way of realizing the intervisibility of two points on the map is by drawing a cross section from one point to another to view the structural appearance of landscape.

If the straight line passes clearly between the two points, it implies the sighting from one point to another not obstructed and hence, the points are intervisible

If the land raises high above the sight line, implies that, the sighting from one point to another obstructed thus, the two end points are not intervisible.

FACTORS AFFECTING INTERVISIBILITY

Intervisibility between points on the map and up on areas on the earth’s surface affected by the following factors.

(a)       Relief: Natural features like mountains, hills and other in between of places affect intervisibility.

(b)       Vegetation: Presence of thick forest in between of two point also hinders interbisibility.

(c)       Buildings: The presences of tall buildings in between two points also affect the intervisibility.

GRADIENT/SLOPE ON A MAP

Gradient/slope is a degree of slope steepness or the ratio between the vertical intervals (increase) to horizontal equivalent; or the amount of rise or fall in meters or feet of the land in relation to horizontal distance.

Gradient is determined by the following principal formula.

Gradient       =          Vertical interval (VI)

                        =          horizontal equivalent (HE)

Where by

VI = Vertical exaggeration; It is the difference in height meter or feet between the highest and lowest altitude of the two recommended points

HE = Horizontal equivalent; It is the distance between the two given points as measured from the map.

PROCEDURES FOR GRADIENT DETERMINATION

(a)    Identify the two points and name them like A and B.

(b)    Join the two points using a straight line to form line AB.

(c)    Measure the ground distance between the two points

(d)    Calculate the actual distance using the map scale given to get the horizontal equivalent.

(e)    Calculate the difference in height between the two point using contours

(f)       Using the formula to have the gradient.

EXAMPLE

Given

High altitude            =          1000m

Low altitude             =          200m

 Gradient      =          Vertical interval (VI)

                        =          horizontal equivalent (HE)

Where by

Vertical rise (VR)     =          High altitude – Low altitude

                                    =          1000m – 200m

                                    =          800m

Horizontal equivalent = 10cm

According to map scale 1:50,000

1cm        =          0.5km

10cm                  = a?

a X 1cm  =  10cm X 0.5km  =  5km

   1cm                  1cm

Gradient           =          800m

                                         5km

To change 5km into meter

1km         =          1000m

5km         =              x

5km         x          1000m           =          5000m

                 1km

Gradient           =          800m

                                         5000m

Gradient           =          1

                                     6.25

Thus, the gradient is 1 in 6.25. This implies there is a rise of 1m high in every horizontal distance of 6.25m from A to B or there is a fall of 1m low in every horizontal distance of 6.25m

TREND/ALIGNMENT OF ELONGATED OBJECT

Alignment is defined as a general direction and bearing of an elongated object on the map and up on the earth’s surface. Elongated object can be like that of a road, railway, ridge and others of the same nature.

Alignment is best described by starting both direction and bearing. E.g. the road align from 45⁰(NE) to 225⁰(SW).

PROCEDURES INVOLVED IN GIVING THE ALIGNMENT

(a)    Identification of the two end points on the topographical map given. The end points can be identified by taking into consideration of the grid reference or place names given.

(b)    Drawing the straight line using a ruler and pencil to join the two end points.

(c)    At the central point of the drawn like mark the four cardinal points.

(d)    Take a protector and measure both degree angles in which the drawn straight line trends.

(e)    Write the alignment starting with bearing followed with direction.

Consider the following case

N

 

The general trend and alignment of the river is from 068⁰(ENE) to 248⁰(WSW)

METHODS USED IN SHOWING RELIEF FEATURES ON

TOPOGRAPHICAL MAPS

Relief refers to the physical appearance of an area by contrasting landforms or variation in shapes and forms of an area over the earth’s surface.

The landforms which make the physical appearance of an area called relief features. These being landforms have defined shape and height above the sea level

The cartographers use to indicate the relief features o maps by employing certain methods which reflect their shape and height per the physical appearance of the area. The main methods employed for this purpose include the following

CONTOURING METHOD

The method involves the drawing of contours on the map face. Contour is an imaginary line drawn on the map face connecting all points of exactly equal height above the mean sea level. The first contoured map was introduced in 1791.

Properties of contour as used for relief representation

(a)    Contour on the maps are numbered either in meter or in feet. The number represents the altitude of different part in the region mapped.

(b)    Contours are drawn in specific interval on the map.

(c)    Contours of different elevations do not cross each other.

(d)    Usually contour lines tend to join around where there is the presence of a rounded landforms like a hill, plateau and others.

(e)    Contours form V shape pointing up or drawn stream to indicate the presence of a river valley.

Merits of contouring method

(a)    Contours are the most popular and widely used method for showing relief on topographical maps.

(b)    Contours show accurate heights of the landforms represented.

(c)    Contours on a map give both shape and altitudes of the relief features of an area represented.

(d)    Provide the basis for hypsometric map construction

Demerits of contouring method

(a)    Sometime contours fail to show certain highest heights due to the limitation of the vertical interval used.

(b)    Some of the landforms are not capable for being represented by means of contour e.g. coral reefs, levees.

(c)    Contours are not suitable for showing relief on a small scaled map.

(d)    It needs high skills to produce contours map.

(e)    Heights given by contours on the map are in specific interval. It is thus sometimes become difficult to assess height of specific interested part.

FORM LINE METHODS

Forms lines are defined as the dotted and unnumbered lines drawn on the map face joining points of approximately the same heights. Form lines are not always plotted at fixed interval and these provide the basis for indication of contours or layer tinting on the map.

Merits of forms lines

(a)    They provide good basis for indication of contours on maps

(b)    They also provide the basis for the indication of layer coloring on the map.

Demerits of forms line

(a)    They need high skill to be plotted on a map.

(b)    They are not commonly appear on topographical map.

LAYER TINTING (LAYER COLORING)

It is one among of the most useful methods for showing relief features on maps. It is done by indicating different colors on the map face, to distinguish zone of altitude. Any layer tinted map should carry a key to interpret the different colors for varied zone of altitude. The common colors for this purpose include the following

(a)    Blue; represents water bodies. Light blue means shallow water and dark blue means deep water.

(b)    Green; indicates lowland of either coastal plain or river valley. Pure green color represents much lowland with altitude from 0 – 200m, while light green represents slightly higher lowland with altitude from 200 – 500m

(c)    Yellow; indicates plateau landscape. Whitish yellow represents low plateau with height from 500 – 1000m, while pure yellow is for higher plateau with height from 1000 – 2000m.

(d)    Brown; indicates highest mountain form 2000 – 4000m or area with permanent ice. 

(e)    Red or pink; indicates very high elevation with height above 4000m.

Merits of the layer tinting method

(a)    It makes a map looks impressive and attractive to the user.

(b)    It is useful method for showing relief on a small scaled map.

(c)    It is associated with the method of trigonometric point.

Demerits of the layer tinting method

(a)    It shows general altitude i.e. does not give the height of specific point.

(b)    It is more expensive to produce the layer colored map.

(c)    The method does not reflect the shape of relief features of an area on the map.

HACHURING METHODS

The method involved the use of hachure. Hachure is a series of small lines drawn on map faces showing the direction and steepness of slope.

 The lines are drawn to follow the slope of the ground or direction in which water would run them.

Merits of the hachuring method

(a)    Hachure easily seen on the map and thus give quick information of the features represented.

(b)    Provide pictorial view of the relief features on a map.

(c)    Show clearly the direction of slopes on the map

Demerits of the hachuring method

(a)    Hide other details as they occupy relatively large space on the map.

(b)    A great skill is needed to produce hachure on a map.

(c)    The method is dying out.

                                                                                                                                           

HILL SHADING METHOD

It is a method of showing relief in which some parts of the map are shaded to indicate the presence of a hill, as they would appear if a light were shining on them. Usually the slopes which face light are shaded lightly while those facing away are in shadow.

Merits of hill shading

(a)    It gives pictorial view to the map user about the hills of an are shown on the map.

(b)    Make a map looks impressive and attractive to the users

(c)    It is very useful method for showing relief on the large scaled map.

Demerits of hill shading

(a)    Does not give height of hills shown on the map

(b)    The shades indicated on the map might hide other details

(c)    It became difficult to determine the gradient of the hill represented so long.

TRIGONOMETRIC POINT

It is a sign triangle with a dot at its center together and height number beside to it. This is noni imaginary method for relief representation on the map as trigonometric stations observed on the ground. The number given with the trigonometric point represents the highest summit of the landscape.

       

                                                                          3211m

                 

●

                                                     

Merits of the trigonometric point

(a)    It is easy to indicate trigonometric point on the map by the cartographer.

(b)    It is non-imaginary method for relief representation on the map.

(c)    Enables the map users to recognize the highest relief height very easily.

Demerits of trigonometric point

(a)    Not easily seen on topographical map.

(b)    Trigonometric point on a map does not give the shape of the relief feature represented.

(c)    They are selective for showing only the highest heights of the relief features represented.

SPOR HEIGHT METHOD

It is a convectional dot (point) together with the height number on a map face. It serves as imaginary method for shoeing relief height as have been measure above the mean sea level. The number shows the height of a relief features shown on the map.

              5678m

Merits of spot height

(a)    It is easily to indicate spot height on the map by the cartographer.

(b)    Enables the map users to recognize the relief height very easily

(c)    It shows the height of hill summits as well as points along the interested structures.

Demerits of spot height method

(a)    Not easily seen on the topographical map.

(b)    Spot height on a map does not give the shape of the relief features represented.

(c)    It is imaginary method for showing relief on a map.

BENCH MARK METHOD

It is a surveyor mark unit indicated on a wall, pillar or building used as reference point in measuring  altitudes or a point of reference used by a surveyor in measuring altitude.

Bench mark indicated on maps following the presence of such mark in the area mapped. Bench marks on maps appear by the convectional letter of BM together with height numbers measured on the ground.

Merits of bench mark method

(a)    It is easily to indicate it on the map by the cartographer.

(b)    It is non- imaginary method for relief representation on the map.

(c)    It show the accurate relief height as it was measured more accurately on the landscape above the sea level.

Demerits of bench mark method

(a)    Not easily seen on the topographical map.

(b)    Bench mark on a map does not give the shape of the relief features represented.

MAP INTERPRITATION

Map interpretation is the science of examining the given topographical map to realize the reliable geographical details of an area represented. Geographical details include climate, economic activities, relief, mode of transports etc.

Map interpretations are done by looking the convectional symbols and sign on the map and know what they stand for. Map interpretation has to entail two basic processes of map reading and map analysis. Map reading is an art of examining the given topographical map to recognize the features that directly appear on the map and map analysis is the art of relating the features that appear on the map to what required to be described, explained or suggested..

In the process of map reading, carefully read and note; the map signs and symbols, north direction, latitude and longitude and other important marginal details.

With map interpretation someone is able to describe and explain the following geographical details; relief, geomorphologic process, drainage pattern, surface rock types, vegetation distribution, communication, population distribution, settlement pattern, climate, human activities and function of urban area.

RELIEF INTERPRITATION ON A MAP

Relief refers to the physical appearance (surface form) of an area by landforms of contracting shape and size.

The realization and description of relief of an area from a topographical map is by observing the patterns of contours and their respective heights.

In common, the relief of an area can be of highland, lowland or coastal relief. The area is recognize be of highland if it is of high altitude above 500m from the mean sea level. Lowland is recognized if the area has low altitude of below 500m from the mean sea level. Coastal relief area is recognized by the presence of ocean or sea.

RELIEF PATTERNS OF AREAS

The common relief patterns recognized from the topographical maps and up on the areas represented include the following

1.   Mountain landscape: On a topographical map is recognized if contours lie so much closer to one another over a considerable wider part. Moreover the map by contours shows many hills or summit, dissection of rivers, the presence of passes, saddle, water shade and escarpment.

2.   Plateau landscape: On topographical map is recognized if the landscape is assessed be of high altitude and wider part is almost level or gentle sloped.

3.   Hilly landscape: On a topographical map is recognized if the contours of roughly round close to one another appear numerous and isolated.

4.   Coastal plain: On a topographical map is recognized if contours on the map are widely spaced and the elevation rarely exceed above 300m.

5.   River basin: On a topographical map is recognized if the mapped areas is observed to lie parallel to the big river and the contours show low height numbers.

IMPORTANT RELIEF DESCRIPTION HINTS

Generally, in making description about the relief of the mapped area, the following hints should be followed

(a)    The map has to be divided into relief regions.

(b)    Give the position location of each relief region as shown on the topographical map.

(c)    Give the general description of each relief region by giving out the prominent landforms and altitudes of each region.

INTERPRITATION OF GEOMORPHOLOGIC PROCESSES

Geomorphologic processes refer to the natural activities (physical processes) which mould an area by resulting into land form development.

Geomorphologic process moulded the area from the topographical map, realized and suggested by taking into consideration of the following

(a)    The presence of volcanic land form such as craters, caldera and volcanic mountain reflects vulcanicity.

(b)    Presence of Block Mountain reflects faulting.

(c)    Presence of escarpment reflect both faulting and denudation.

(d)    Presence of saddle reflects folding.

(e)    Presence of rivers and lakes suggests erosion and deposition.

(f) Presence of ocean and sea suggest erosion and deposition

INTERPRITATION OF SURFACE ROCKS

Rocks are the aggregate or mixture of materials in solid form contented with minerals. Rock are extremely varied and popularly include; igneous, sedimentary and metamorphic rocks.

The surface rocks of an area are not directly shown on topographical maps. Rock types can be identified by taking into consideration of the following

(a)    Landforms: landforms are good guide to surface rock type identification of an area from a topographical map as follow

·            The presence of volcanic landforms on the map like crater, caldera and other reveals the igneous rock.

·            The presence of coral reef reveals the organically formed sedimentary rock.

·            The presence of depression, sand dunes, and beaches reveals the sedimentary rocks.

·            The presence of conical hills reveals the igneous rocks.

(b)    Drainage system: Drainage in any area strongly related to the nature of geology. It is thus; consideration of drainage may help to suggest the type of rocks of an area.

·            The presence of dendritic, parallel and radial drainage patterns indicate the presence of hard rocks.

·            The presence of resurgent drainage of rivers indicate the existence of permeable rocks

·            The presence of swamps indicate the existence of impermeable underlying rocks

(c)    Vegetation covers: Certain vegetation much related to geological nature of areas. Therefore; the consideration of vegetation may help to suggest the nature of rock of an area.

·            The presence of thick forest and crops of coffee and tea suggest the existence of igneous rock

·            The presence of poor vegetation suggests the existence of sedimentary rocks.

INTERPRITATION OF DRAINAGE PATTERN

Drainage is the removal of surface water from an area by the system (layout) of both natural and manmade water bodies like of rivers, lakes, swamp, canals and other related system.

The common drainage pattern (river) of areas which normally observed on the topographical maps include the following

1.   Dendritic pattern: it is a drainage pattern of an area with tributaries converged to the main river at acute angle resembling the shape of a tree like a feature. It develops on landscape of uniform rock hardness and structure. It is very common in areas of igneous rocks.

                                                                                          

2.   Trellis or rectangular drainage pattern: It is pattern which occupies the shape of a lattice with tributaries converging to the main river at almost right angle. It develops on a catchment’s area whose landscape is with variation in rock hardness and structure.

                                                                                                                                         

3.   Radial pattern: It is a drainage pattern whose tributaries diverge outwards down form from the summit of rounded high land of different direction.

It forms the shape of spokes round a wheel like structures. It is common to areas of roughly circular hills of igneous rock.

                                                                                                                                                

4.   Centripetal pattern: It is the one whose tributaries flow different directions converging at a center of down warped landscape, where is a swamp or lake. It is largely controlled by the shape of the landscape.

                                                                                                                                               

INTERPRITATION OF VEGATATION DISTRIBUTION

Vegetation refers to the total assemblage of plant covers in an area. Topographical map shows vegetation with reflection to actual areas represented. Vegetation shown on topographical can be divided into natural and artificial vegetation

The forms of natural vegetation which can be observed from the topographical maps include the following

(a)    Forests: the vegetation largely dominated by dense growth of tall trees with closed leaf cover or canopy. These develop in regions where the amount of rainfall is heavy.

(b)    Woodland: The type vegetation formed by less closely spaced shorter trees. These grow in areas of moderately high rainfall.

(c)    Thicket: This type of vegetation is of dense shrubs and scattered low trees and commonly found in region of moderately seasonal rain.

(d)    Mangrove: These are the salty trees found in areas along the shores of coasts line.

(e)    Scrubs: The vegetation of much low lying trees commonly found in areas of long dry season.

(f)       Scattered trees: These are the vegetation of widely spaced trees. These also commonly found in areas of seasonal rainfall.

(g)    Planted vegetation: These are more particularly of the cultivated plants (crops) like sisal, tea, coffee, and scattered cultivation.

ACCOUNT FOR THE VEGETATION DISTRIBUTION

Some time you may be asked to account for the distribution of vegetation of an area covered by the map. This means that you give reasons why different types of vegetation occur in different areas. There are several factors that may influence vegetation distribution. These are

(a)    Climate: Areas that receive heavy, well distributed rainfall are covered by forests and bamboo vegetation. The presence of woodland suggests moderate rainfall while scrub and scattered trees indicate low, unreliable and season rainfall.

(b)    Relief and soil: Relief influences the distribution of vegetation in that very steep areas are usually not covered by any vegetation. This is because the area covered by very thin, infertile soils which cannot support plant. On the other hand gentle slope are covered by different types of vegetation because they have deep fertile soils. Very high altitude experienced very low temperature thus inhibiting plant growth.

(c)    Man’s activities: Some areas on the map may not covered by vegetation as a result of man’s activities. These may have been cleared to give room for cultivation and settlement.

(d)    Other factors: Areas along river valley have riverine vegetation because the water table is close to the surface. Also, swamps have vegetation due to the availability of water.

IMPORTANT VEGETATION DISCRIPTION HINTS

To describe vegetation, carefully study the key to recognize the convectional symbols represent vegetation and relate to map face. After this the following hints can be given

(a)    Identify the types of vegetation shown on the map whether natural vegetation or artificial vegetation.

(b)    Give the nature of plant cover observed on the map.

(c)    Give the distribution of each identified type of vegetation and its position.

(d)    Describe the extent of coverage of each identified type of vegetation.

INTERPRITATION OF CLIMATE

Climate is the average weather condition experienced in an area throughout. Climate has a good number of elements and most pronounced ones are of rainfall and temperature.

Topographical map, show little direct climatic details of areas represented. It is thus identification and description of climate of an area from the topographical map is by taking into consideration of the guiding facts related to climate which can easily observed on the map. These include the following.

1.      Latitude: Climate conditions vary consideration from one natural region to another. It is thus; if the natural region in which the mapped area is found observed. The natural region is recognized by taking into consideration of the latitudes indicated long the map edge.

Examples

·         If the mapped are understudy is located from or in between 0⁰ – 5⁰ north and south of the equator, it implies that, the area is located in the equatorial region.

·         If the map along its edge shows any latitude in between of 6⁰ – 20⁰ north and South of the equator, it implies the area represented on the map located in tropical region.

2.      Altitude: Altitude has a considerable impact on climate as temperature and rainfall regime is influenced by altitudes. It is therefore the consideration of altitude of an area from the map, may help to suggest the likely climatic condition.

Examples

·         If the altitude is higher mostly above 2000m implies the area represented is of highland and likely to experience highland climatic pattern of most wet cool conditions.

·         If the contours and other means show low height numbers, give an impression that, the area is of lowland and likely to experience high temperature.

3.      Water bodies (drainage): Drainage is very good guide to climate particularly on the relative amount of rainfall. It is so as the sources of water bodies in any area on the earth’s surface is mostly by the amount of rainfall received.

Examples

·         Presence of the salt lakes, seasonal stream, and bore hole suggests that, the rains in the area are seasonal with long period of dry condition.

·         Presence of abundant permanent streams and permanent swamps, suggests heavy rainfall received in the area.

·         Presence of the sea, suggest maritime (coastal) climate

4.      Natural vegetation and crops: Natural vegetation and crops shown on the map have reflection to climate and thus; is also good guide to climate.

Example (natural vegetation)

·         Presence of thick forests in a map indicates heavy rainfall.

·         Woodland vegetation indicates moderate rainfall.

·         Scrubs, thickets and grassland indicate dry condition.

Examples (crops)

·         Presence of cotton, sisal and cashew nuts suggest moderately high seasonal rainfall and high temperature

·         Presence of coffee and tea on the map and up on the area represented, suggest cool wet climate.

INTERPRITING HEMISPHERE ON A MAP

In the globe, usually hemisphere is divided into two types which are southern hemisphere and northern hemisphere. Southern hemisphere is located at south toward the South Pole and northern hemisphere is located at north toward North Pole.

In interpreting the hemisphere in which the mapped are is located, the most important thing to consider is latitude line. Hemisphere varies consideration from one natural region to another. It is thus; if the natural region in which the mapped area is found observed. The hemisphere is recognized by taking into consideration of the latitudes indicated long the map edge.

Important thing to know, all topographical maps which the region especially Africa is taken in the southern hemisphere but remember to consider line of latitude at the mapped edge as your evidence.

INTERPRITATION OF COMMUNICATION ON A MAP

The term communication in map reading perspectives is concerned with the means of transport like roads, railways, airways and waterways. It also includes the telephone lines.

On topographical maps may show one or more forms of transport with reflection to areas represented. This include the following

1.      LAND TRANSPORT: This form of transport is by road, tracks, railway line and foot path.

(a)    Roads: These are of the varied nature and include the following

·      All weather roads bound surface: These are tarmac roads. These normally used throughout the year including during the rainy season.

·      All weather road loose surfaces: These are the roads whose surface covered in murram. These also can be used throughout the year.

·      Dry weather road: These also covered in murram but they are only reliable in dry season.

·      Motor able tracks: These do not fall in the category of roads, but they can be used by motor vehicles especially in dry season

(b)    Footpath: These are the ways through which people move from one area to another on foot.

(c)    Railway transport: It is reflected by the presence of railways; and these may appear on the topographical map provided. Railway line as observed from the topographical map with reflection to areas represented, are of two categories and include the following    

·      Main railway lines: These on the topographical maps represented by the black shading which alternate with white ones.

·      Light railway lines: These are normally present with in plantation and mining areas. These are presented by the thin black lines which may be pecked.

2.      AIR TRANSPORT: Air transport about areas can be realized if the following observed from the topographical map

(a)    Airport:  This is a large area on the ground which is used by commercial airlines to land or take off.

(b)    Aerodrome: This is small airport that is mainly used by private air craft.

(c)    Airfield: This is an area of open and level ground where aircraft may land or take off. Air field runway can be bound, murram or grass.

3.      WATER TRANSPORT: Water transport on the topographical map with reflection to the area represented reveled by the presence of ports, big lake, sea, and ferry across the river, lake or part of the sea.

INTERPRITATION OF SETTLEMENT PATTERNS

The signs showing settlements on maps are observed be in varied arrangement. With respect to this, settlements on topographical map and up on the areas represented recognized be in varied pattern. The most common pattern include the following

1.      Dispersed settlements patterns: It is alternatively called scattered settlement pattern. The houses are widely spaced one to another. It is very common in areas of the following nature

·         Scattered cultivation

·         Individuals farms are large enough and population is too sparse

·         Pastoral society

·         Evenly distributed of water sources.

             

2.      Nucleated settlement pattern: Houses and other related forms are compacted to one another. On the topographical map, this is identified where the round black dots lie clustered or specific area. This pattern is common in areas of the following nature

·         Urban area where people more concentrated

·         Planned villages

·         The presence of economic factor like industrial factor

·         Presence of social services/amenities

3.      Linear settlement pattern: This pattern, the dwellings are concentrated along elongated objects of economic significance like a road, river, and railways or along the coast.

                                                         

IMPORTANT SETTLEMENT DESCRIPTION HINTS

(a)    Give the statement in connection to what are you need to describe from the map about settlement.

(b)    Identify the main types of settlement pattern in the area as observed from the map whether linear or nuclear.

(c)    In each type give the distribution and if possible the influencing factors.

INTERPRITATION OF HUMAN ACTIVITIES

Human features on topographical maps reflect human activities taking place in the area covered by map. Many are in form of land use which refers to the ways in which land is utilized in the area

Human activities on topographical maps in divided into two groups which are economic activities and social activities. Economic activities include fishing activities, farming activities; trade activities etc. and social activities include health services, education services, security services etc.

ECONOMIC ACTIVITIES

(a)    Farming activities: This is indicated by the presence of large scale farms like sisal, tea, coffee etc. presence of Ural settlement, presence of market, sugar juggleries, also presence of river or dam which show the irrigation.

(b)    Pastoralism activities: This is suggested by the presence of grassland vegetation, scrubs, markets, scattered clusters of settlement, water hole, bore hole, dams, and water pumps, presence of ranches and dairy farms and veterinary centers.

(c)    Fishing activities: This is evidenced by the presence of dense settlement along the shores of lakes or ocean, together with fish traps, ponds, fish fillet factories, fishing cooperatives and fishing department. It would be wrong to suggest that there is fishing in a region just because of the presence of rivers, lakes or oceans. Evidence must be cited on the map.

(d)    Lumbering/forestry activities: This is indicated by the presence of forests, saw mill, minor road ending into forests, woodland, scattered trees and forest guard posts. However, some forests are reserves and therefore no lumbering may be allowed.

(e)    Trade activities: This suggested by the presence of township, transport network of road and railway together with settlement, presence of a wide variety of economic activities, presence of airports, sea or lake ports, markets and shops.

(f)       Tourism activities: This indicated by the presence of historical sites like museums, attractive landforms like crates, mountain, beaches, conical hill, also presence of hotels, national parks, game reserve and forest reserve.

(g)    Manufacturing industries: This can be observed on the map by the presence of factory special symbols which indicated on the map, presence of township by having high concentration of transport network, presence of markets, transports and industrial area.

(h)    Mining and quarrying: This can be suggested by observation of the presence of the convectional signs indicating minerals work, presence of lakes in valley and presence of quarries.

SOCIAL ACTIVITIES

(a)    Health services: This can be indicated by the presence of hospitals and dispensaries.

(b)    Education services: This can be suggested by the presence of schools, college and universities.

(c)    Religion services: This also can be indicated on the map by the presence of church and mosque.

(d)    Security services: This also can be indicated on the map by the presence of army camp, police office etc.

(e)    Administrative services: This also can be suggested on the map by the presence of DC office, RC office, PO etc.

(f)       Transport and communication: This also can be indicated on the map by the presence of road, railway, telephone line and other means of transport.

INTERPRITATION OF POPULATION DISTRIBUTION

Population distribution refers to the total number of people living together in a certain geographical area. Also it can be defined as occurrence or non-occurrence of people in certain geographical unit.

Population on topographical map is unevenly distributed over the area such that some areas have low density, other have medium density and areas have high density population. This is due to the following factors

(a)    Relief (topography): Where the slope is steep there is low or no population due to poor soils and nature of the land but where there are gentle slopes or flat surface there is high population. Highland normally attracts population compare to lowland.

(b)    Climate: Area with reliable rainfall has attracted high population, but where there is poor rainfall there is low population. Also the area with very high or very low temperature does not attract population while the areas with moderate temperature attract population.

(c)    Vegetation: In areas where dense vegetation people are discourage to live leading to sparse population or no population at all. dense vegetation hinders penetration of communication and development.

(d)    Social services: Area that have enough social services like health services, educational services, security services tend to have high dance population compare to the area which has few social services.

(e)    Accessibility: The area that have good transport and communication network such as town area tend to have high population compare to the area which has poor transport and communication network like Ural area.

FUNCTIONS OF TOWN

(a)    Some towns are trading center indicated by the presence of sores, roads, shops and market.

(b)    Other towns may be administrative centers suggested by the presence of police posts, D.C office, D.O office, court houses etc.

(c)    They can be educational centers indicated by the presence of school or colleges.

(d)    They can be transport and communication centers evidenced by the presence of dense network of road, railway lines, airports, sea or lake ports, post offices, telephone lines

(e)    They can be health centers indicated by the presence of hospitals and dispensaries.

(f)       Others are industrial centers indicated by the presence of factories.

(g)    Some towns are agricultural centers evidenced by the presence of sores, depots etc.

(h)    Town may be cultural center indicated by the presence of theaters

(i)        The may be mining centers suggested by the presence of quarries, mineral work, mines etc.

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BIBLIOGRAPHY

KINUNDA, J.E. & MSABILA, D.T. (2008), Practical Geography for Secondary School Book four. Nyambari Nyangwine Publisher. Dare es salaam

KIMEI, M. & WANJAU, D. (2004), School certificate Geography. East Africa Education Publishers. Kenya

MSABILA, D. & KINUNDA. J, (2009). Geography for Secondary School form 3 student. Nyambari Nyangwine Publisher. Dare es Salaam

MZEZELE, S. & KIBUUKA, P. (2004). Geography in Focus form 3. Oxford University Press (T) limited. Dare es salaam.

MTEGETWA, A.M. (2010). Topographical Maps interpretation, lesson notes. Mtegetwa Publishing Unit. Dare es salaam.

KAMILI, Z.M. (2008). Pactical Geography alive. Dare es salaam. Tanzania