MAP READING AND INTERPRETATION
What is a map?
Map: is the representation of a part of the earth surface or the whole earth surface by using small flat materials such as a sheet paper, wall, piece of wood, piece of cloth or any other materials that can be drawn.
Map interpretation: is the process of relating the informations found on the map with respect to the actual features on the earth surface.
Map analysis: is the process of examining the given topographical map so as to identifying both natural and manmade features found on the map.
Map reading: is the process of relating the identified information on the map and actual features found on the earth surface.
IMPORTANCE OF MAP TO THE GEOGRAPHERS
1. It provides basic geographical information.
2. It used by pilots and navigators to reach their direction.
3. It used to store geographical information for the future use.
4. It helps in field studies/research.
5. It used for land use planning such as agriculture.
6. It used in military purposes e.g. during wars.
7. It helps to indicate various human activities such social, economic and political activities.
WEAKNESS/DISADVANTAGES/LIMITATION OF USING MAP
1. Map production is very expensive: Normally map production or making especially topographical maps need enough money or capital.
2. Time consuming: Both during production (cartographic processes) and on interpretation.
3. Map is selective. Hence it cannot show all features in a given area.
4. Map making and interpretation need high skills: Hence it cannot be produce and interpreted by anyone.
5. It cannot show the real features: This is due to the fact that map shows its features by using symbols and signs.
MAIN TYPES OF MAPS
1. Topographical maps: Are maps which shows both natural and man made features. Example: which are natural features e.g. mountains, valleys, hills etc. and manmade features. Example: bridges, ponds, roads, settlements etc.
2. Statistical maps: Are maps which show the distribution of things in quantitative manner e.g. distribution of rainfall, temperature, crops etc. Examples of statistical maps are dot maps, Isopleths maps, isoline maps etc.
OTHER TYPES OF MAPS
1. Large scale maps: Are those maps drawn to large scale size e.g. 1:10000. These maps gives a larger representation of small area, they are also more detailed (shows a lot of information). They represent areas like cities, towns and villages.
2. Medium scale maps: Are those maps drawn to medium scale size e.g. 1:100000. They show a moderate amount of details. They represent areas like districts, regions and countries.
3. Small scale maps: Are those maps drawn to small scale size e.g. 1:50000. They give a small presentation of a large area; they show little content (little information). They represent areas like continents and the world.
CONTENTS OF THE MAP
Contents of the map: Are the information which are shown on the map which can either natural, artificial or supportive contents.
TYPES OF MAP CONTENTS
i. Natural contents.
ii. Artificial/man-made contents.
iii. Supportive contents.
A. NATURAL CONTENTS/INFORMATIONS/FEATURES
Natural contents/features: Are those natural informations found on the natural environment which are not influnced by man.
Example natural contents/informations
i. Relief features or landforms (mountain, hills, vallyes, saddles, basin, slopes, depressions).
ii. Vegetation (forests, bamboos, thickets, srcrubs).
iii. Water bodies (lakes, rivers, seasonal swamps, ocean dams, etc).
iv. land surface.
A. RTIFICIAL FETURES/CONTENTS
Artificial or man-made features: Are those features or informations which are found on the map as result of man made.
Example of artificial features
i. Roads.
ii. Railways.
iii. Settlements.
iv. Crops like tea, coffee, cotton, sisal, etc.
v. Bridge
C. SUPPORTIVE CONTENTS/BASIC ELEMENTS OF A GOOD TOPOGRAPHIC
MAP/ESSENTALS OF THE MAP/MARGINAL INFORMATION OF THE MAP
Map supportive contents: Are essentials of the map which guide the map users to use the map in a proper way. The basic skills required in understanding how to read a map include;
1. Tittle: it helps to identify the place where the map was produced. E. Arusha sheet, Korogwe sheet.
2. Scale: is the ratio between the map distance and the actual ground distance e.g. 1:50000
3. Key/ legend: it used to identify the various signs and symbols used on the map.
4. North direction: It used to locate the direction of place on the map.
5. Margin/Frame:This is the frame which used to show the boundary of the map.
6. Date of compilation: This used to indicate the time when the map was produced. Example 1986.
7. Publisher name: It used to show the name of institution or organization published the given map.
Example: The ministry of land in Tanzania.
FACTORS THAT AFFECT/ DETERMINE THE CONTENTS OF THE TOPOGRAPHICAL MAP
1. Purpose of a map/cartographer: Normally the appearence of difference features on the map is largely depends on the purpose of the cartographer. Aim of the cartographer determines what to be shown on a map since map is selective.
2. Scale size of the map: Maps are drawn 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
3. Date/time of compilation/production: Normally map is likely to show information which was represent by the time when it was prepared. Therefore two maps produced at different time at the same place are likely to be differ in terms of their contents because the landforms and other features are dynamic in nature.
4. Different in environment: A map shows what is found at a given place and not otherwise therefore maps of different places are likely to be differ in terms of their contents.
5. The nationality of the cartographer: The map produce by the foreigner or indigenous cartographer are likely to differ in contents. The foreigner cartographer might not include same contents because of being not familiar with the area.
THE MAP SCALE
Scale: is a ratio between the map distance and the ground distance. E.g 1:50000.
TYPES OF SCALES
Scales are classified according to their size.
i. Small scales
ii. Medium scales
iii. Large scales
1. SMALL SCALE
Are those scales that cover large area.
i. It represented by small measurement on ground.
ii. It. It show small size features.
iii. They consist many contents.
Iv. The map scale range from 1:250,000 to 1:1000, 000.
2. MEDIUM SCALE MAP
These are scales which rage between the large and small scale.
i. It represent relative large area. example villages, districts or town.
ii. They shows moderates contents.
iii. The map scale range from 1:50,000 to 1:250,000.
3. LARGE SCALE MAP
These are scales that coverd small area such as village, school, streets etc.
i. They represents very few features.
ii. They are used to represents small ground areas.
iii. The map content is enlarged and they are clearly seen.
iv. The map scale range from 1:5000 to 1:25000.
METHODS USED TO EXPRESS SCALE
There are three types of methods used to express of scales
i. Statements scale
ii. Representative Fraction (RF) scale.
iii. Linear (graphic) scale.
1. STATEMENT SCALE
Statement: is the method of expressing scale by usin words or verbs. E.g. one centimeter on the map represents ten kilometer on the ground. This can also be expressed in short as 1cm represents 4km or 1cm to 4km.
2. REPRESENTATIVES FRACTION (RF) SCALES
Representative fraction scale: is the method of expressing scale by using ratio and fraction (e.g. 1/50,000 fraction) or ratio (e.g. 1: 50, 000 ratio).
Therefore, R.F. scale = 
3. LINEAR (GRAPHIC) SCALES
linear or graphic scale: is the method of expressing scale by using which is subdivided into smaller equal units. There are two kinds of linear scales: the short line scale and the long line scale.
i. A short line scale: it consist 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. E.g
ii. A long line scale: it consists of a long line that is divided into several equal parts. It has two sections. Normally the linear scale is divided in to two parts which are
a). Primary scale: it located to the right hand side of the graph which is expressed in Kilometers (KM).
b). Secondary scale: it located to the left hand side of the graph which is expressed in Meters (M).
SCALE CONVERSION
Scale conversion: is the technique of changing map scale from one form of expression scale into another. Normally the cases include the following:-
1. Conversion of Representatives scales (R.F) into statement scale.
Example: Given a Representatives fraction scale of 1:50,000 convert it into a statement scale.
Solution
Therefore 1cm on the map represents 0.5km on the ground.
2. 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
3. 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.
Let your line is 5km
Therefore 1cm represents 0.5km
IMPORTANCE OF MAP SCALES
1. It help to determine the relationship between the map distance and the actual ground distance.
2. It used to calculate distance.
3. It used in measurement of area.
4. It used in land use planning.
5. Scale is used to calculate gradient and vertical exageration.
METHODS USED TO LOCATE THE POSITION OF THE PLACE ON THE MAP
1. The place name: This is method use the specific names of physical features on the map to indicate their direction. E.g, Arusha, Tanga.
2. Latitude and longitudes: these are lines drawn on the map which ecpressed by degree, minutes and seconds to measure the durevtion of the place. However latitude are horizontal line running from west to south on the map while longitudes are vertical lines. E.g 0-5N/S, 5-15N/S, 15-30N/S.
3. Grid system numbers: Are numbers which show the position of physical features, most large scale topographical maps having vertical and horizontal lines drawn on them. Grid lines are drawn for the specific purpose of facilitating map reading especially fixing positions on the map. Vertical lines are called Eastings; they are numbered towards the east. Horizontal lines are called Northings. They are numbered towards the north.
5. North direction
Direction: is method of locating the position of the place by using cardenal points.
Normally direction on the map can be given in four, eight or sixteen cardinal points of compass and their corresponding bearings.
6. The compass bearing
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. The method is mostly used to establish the location of a place from another place by giving the degree angle measured clockwise from north.
PROCEDURES FOR DETERMINING BEARING
i. 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.
ii. 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.
iii. 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.
iv. Take the protector and measure the angle of an observation line that connects the two points clockwise from north direction.
v. Read the angle in three numbers.
The bearing of point B from point A is of about 045 Types of bearing
i. Back bearing: is the bearing which measured from the object to the observer.
ii. Foward bearing: is the bearing which measured from the observer to the object.
Rules/ procedures of calculating back bearing BB = FB + 1800 if less than 1800
BB = FB – 1800 if the FB is greater than 1800
NB: 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.
TREND AND ALIGNMENT OF ELONGATED OBJECT
Alignment: is defined as a general direction of elongeted on the map and the earth’s surface. while trend: refers to the bearing of an object.
Normally the 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. Example: the road align from 450(NE) to 2250(SW).
PROCEDURES INVOLVED IN FINDING THE ALIGNMENT
i. 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.
ii. Drawing the straight line using a ruler and pencil to join the two end points.
iii. At the central point of the drawn like mark the four cardinal points.
iii. Take a protector and measure both degree angles in which the drawn straight line trends.
iv. 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)
CORRECTION OF ERROR/DISCREPANCY OF READING BEARING
Errors: is the mistake or shortcoming that occurs during the measuring bearing. Correction of errors is done with the use of the mean error by considering the varied cases. Mean error is computed by making the following application.
Steps of correcting errors
In order to correct error or discrepancy we should consider the mean error of reading
i. To find the difference of reading (bearing, angle). Example 2630 – 0770 = 1860
ii. To show the error of reading.
Example Error = 060
iii. To find mean error. Example Mean error
Mean error Mean error 0
iv. To find new forward bearing and new backward bearing. Example
New forward bearing (FB) = Old FB+/- mean error
2630 – 030 = 2600
New backward bearing (BB) = Old BB + Mean error
0770 + 030 = 0800
New forward bearing is 2600 and backward bearing is 0800 Therefore 2600 – 0800 = 1800
MEASUREMENT OF DISTANCE AND AREAS
Distance: is the length between the two points on the earth surface. It is normally expressed in kilometer and miles.
The tools/ methods include the following. In this case, the following devices are used:-
1. A pair of divider: a pair of divider is commonly used to measure short distance.
Transfer the segments to already drawn straight line.
Then transfer the line to the linear scale or ruler for calculation to get actual distance.
2. Piece of thread: Slowly lay a piece of thread along a giving length. Then transfer the string or thread to the linear scale or ruler for calculation to get actual distance.
3. A piece of 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
Therefore the distance of road from grid reference 123433 to grid reference 6786765 is 11.75km
MEASUREMENT OF AREAS SIZE
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.
1. AREAS OF 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.
i. 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
ii. 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
iii. 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
2. AREA OF IRREGULAR FEAGURES
Area of regular shape: 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
i. Square/ grid method: This is the most accurate and most widely used method. Gridreference square is normally used
Procedures/steps
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
Therefore the total area covered by forest is 6km2
ii. Strip/division method: This is less accurate method. It’s normally used when the map has no grid lines on its face.
Steps to be considered
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
iii. 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
IDENTIFICATION OF THE RELIEF FEATURES ON THE MAPED AREA
The area shown on the map can be characterized by presence of various features in both low land and high land features. Those are
i. Mountain, hills, craters.
ii. Water bodies.
iii. Forests.
iv. Plains.
v. Settlements such, roads, railways, population, etc.
METHODS USED TO SHOW RELIEF FEATURES ON THE MAP
1. CONTOURING METHOD
Contour: is an imaginary line drawn on the map face connecting all points of exactly equal height above the mean sea level. Contour method: The method involves the drawing of contours on the map face. It used to show the height of the place above the sea level.
Merits of contouring method
i. They used for showing relief on topographical maps.
ii. Theu show accurate heights of the place above the sea level.
iii. They give both shape and altitudes of the relief features of an area.
Demerits of contouring method
i. Sometime contours fail to show certain highest heights due to the limitation of the vertical interval used.
ii. Some of the landforms are not capable for being represented by means of contour
e.g. coral reefs, levees.
iii. Contours are not suitable for showing relief on a small scaled map.
iv. It needs high skills to produce contours map.
v. Heights given by contours on the map are in specific interval. It is thus sometimes become difficult to assess height of specific interested part.
2. 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.
3. 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:-
Blue: represents water bodies.
Light blue means shallow water and dark blue means deep water.
Green: indicates lowland of either coastal plain or river valley.
Pure green colour: represents much lowland with altitude from 0 – 200m, while light green represents slightly higher lowland with altitude from 200 – 500m.
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.
Brown: indicates highest mountain form 2000 – 4000m or area with permanent ice. ink/shading: indicates very high elevation with height above 4000m.
Merits of the layer tinting method
i. It makes a map looks impressive and attractive to the user.
ii. It is useful method for showing relief on a small scaled map.
iii. It is associated with the method of trigonometric point.
Demerits of the layer tinting method
i. It shows general altitude i.e. does not give the height of specific point.
ii. It is more expensive to produce the layer colored map.
iii. The method does not reflect the shape of relief features of an area on the map.
4. 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
i. Hachure easily seen on the map and thus give quick information of the features represented.
iii. Provide pictorial view of the relief features on a map.
iv. Show clearly the direction of slopes on the map.
5. 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
i. It gives pictorial view to the map user about the hills of an are shown on the map.
ii. Make a map looks impressive and attractive to the users.
iii. It is very useful method for showing relief on the large scaled map.
Demerits of hill shading
i. Does not give height of hills shown on the map.
ii. The shades indicated on the map might hide other details.
iii. It became difficult to determine the gradient of the hill represented so long.
6. 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.
Merits of the trigonometric point
i. It is easy to indicate trigonometric point on the map by the cartographer.
ii. It is non-imaginary method for relief representation on the map.
iii. Enables the map users to recognize the highest relief height very easily.
Demerits of trigonometric point
i. Not easily seen on topographical map.
ii. Trigonometric point on a map does not give the shape of the relief feature represented.
iii. They are selective for showing only the highest heights of the relief features represented.
7. SPOT HEIGHT METHOD
i. 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.
Merits of spot height
i. It is easily to indicate spot height on the map by the cartographer.
ii. Enables the map users to recognize the relief height very easily
iii. It shows the height of hill summits as well as points along the interested structures.
Demerits of spot height method
i. Not easily seen on the topographical map.
ii. Spot height on a map does not give the shape of the relief features represented.
iii. It is imaginary method for showing relief on a map.
8. 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.
Merits of bench mark method
i. It is easily to indicate it on the map by the cartographer.
ii. It is non- imaginary method for relief representation on the map.
iii. It show the accurate relief height as it was measured more accurately on the landscape above the sea level.
Demerits of bench mark method
i. Not easily seen on the topographical map.
ii. Bench mark on a map does not give the shape of the relief features represented.
IDENTIFICATION OF CLIMATE ON THE MAP
Relief: Refers to the general physical apperance of the area shown on the map.
Climate: is the average weather condition experience in a given area over a long period of time not les than 30 years. Topographical maps may be used to identify the climate of given mapped area. The following clue may be employed to identify or depict the type of climate on a given area.
1. LATITUDE
0-5N/S of the equatorial imply wet-hot climate particularly EQUATORIAL CLIMATE 5-15N/S of the equator may suggest TROPICAL CLIMATE with seasonal rainfall.
15-30N.S of the equator imply SEMI-DESERT
30-40 N/S
IMPLIES DESERT CLIMATE or MEDITERRANEAN CLIMATE
2. ALTITUDE
-Look on the contour height on mapped area. If the area experience high rainfall and implies. MOUNTANEOUS CLIMATE.
3. WATER BODIES
Presence of salt lake, waterhole (wh), bore hole (bh), seasonal swams, all these implies semi-arid climate.
Presence of many streams in relation to the altitude indicates area that the area receives heavy rainfall.
4. VEGETATION
Is the collection of total plant cover on the earth surface that can be natural or artificial.
-presence of dense forest (tall trees) and bamboo indicate wet climate (equatorial climate or modified equatorial climate).
-presence of scattered woodland vegetation indicate tropical climate.
-presence of scrub/shrubs(thorn forest )and thicket(closely set tree)indicate semi- desert or desert
5. CROPS:
Presence of sugar cane sisal cotton I n the absence of irrigation suggest semi-Arid or dry climate. Note (sometimes range from tropical to semi arid with consideration of other factors). The presence of palm tree indicate Wet-warm climate
Presence of millet and sorghum imply semi-Desert
CROSS SECTION AND INTERVISIBILITY
A cross section: is the way of showing relief features from one point to another point.
DRAWING CROSS – SECTION
A cross – section: is a graphic representation of the relief features based on heights shown by contours on a map exactly. 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. Normally cross – section can show both natural and human features like river, road, railway, vegetation may be marked and named.
Types of cross section
Cross – sections are of two types and include:-
i. Simple relief or cross profile: This is the type of cross section which show few details. 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.
ii. The annotated cross section: Is the the type of cross section which is drawn to scale and the position of important places and features are crossed between two points indicated more accurately. These are such as river, vegetation, railway, road or any features. It is also known as accurate cross section which means cross section which show more details.
iii. Sketch transcend cross- section: is the cross section which is used for showing only highest and the lowest point. It normally portray a rough picture of general appearance of the landscapes.
PROCEDURES OF CONSTRUCTING CROSS SECTION
The construction of cross section should fundamentally follow the following significant procedures or steps:-
1. 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.
2. Draw the straight line with the use of ruler on the map to join the two point identified.
3. 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:-
1. The two end points, which have been identified on the map
2. Where every contour line cuts the line
3. The contour heights
4. The important landscape features of both natural and manmade feature
4. Find the appropriate vertical and horizontal scales.
5. Construct the frame work for drawing the cross section. The frame work should have both vertical and horizontal line distances.
6. 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.
7. Connect the plotted points with pencil using the free hand to develop the structural appearance of the landscape.
8. Finish the cross section by including the following:-
i. Heading to show what the cross section is for about.
ii. Natural and manmade features which show the clear outlay of what represented by the cross section.
iii. Vertical scale; this show the relationship of altitudes between the cross section and the actual ground represented.
iv. Horizontal scale; this shows the relationship of horizontal distance between the cross section and landscape represented.
Cross section from point A to B
IMPORTANCE/SIGNIFICANCE OF CROSS SECTION
i. 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.
ii. 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.
iii. It shows clearly the altitudes of the different parts of the landscape in between of the two points in the area.
iv. Cross section aid to make gradient determination of the sloped landscape by relating VI and HE.
INTER VISIBILITY
Intervisibility: Is the ability to see two points at the same time. 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.
i. Relief: Natural features like mountains, hills and other in between of places affect intervisibility.
ii. Vegetation: Presence of thick forest in between of two point also hinders interbisibility.
iii. Buildings: The presences of tall buildings in between two points also affect the intervisibility.
VERTICAL EXAGGERATION [V.E]
Vertical Exaggreration: is a the different between horizontal and vertical scale in which the vertical scale is larger than the horizontal scale
.
Formula
When drawing a cross section of a portion of a plateau it is important to choose a reasonable vertical scale in relation to the horizontal scale so that pictures drawn shouldn’t appear too big or too small.
Horizontal scale is the map scale/ ground scale.
When calculating VE both HS and VS should be the same units of measurements.
For example: if a map scale were 1cm to 100000cm and the vertical 1cm to 100m, the VE is first converted from 100m to cm
= VE=10.
It is important to note that inter visibility can be affected by other factors such as buildings or vegetation and also higher land.
GRADIENT
Gradient: is the measure of slope.
Gradient/ slope: are measured by comparing vertical distance to the horizontal distance. In map reading the calculation of gradient is done by comparing the vertical interval between two places and the horizontal distance between them.
Vertical interval: Is the difference in height between the two contour lines on the map. V .I= highest contour - lowest contour
The horizontal distance: is the length between two points. It is measured on the map by converting map scale into ground distance by the use of the map scale.
In calculating gradient both vertical and horizontal lengths must be brought to the same unit of length.
The formula for gradient is Formula
Gradient = 
CALCULATION OF GRADIENT
EXAMPLE 1
If the highest contour is 700m and the lowest contour is 300m, and the vertical interval (V.I) is 400m, hence the Length from point A to B is 8.4 cm. Calculate the gradient if the map scale is 1cm to 2km.
Solution
Step 1: Change 8.4cm into ground /map scale 1cm to 2km
8.4cm to x
=16.8km
Step2: Change the ground scale into meters 1km=1000m
16.8km=?
=16800m
Step 3: find the gradient
Gradient = G =
Gradient= 1/42
IDENTIFICATION OF DRAINAGE SYSTEM AND PATTERN ON THE MAP
Drainage is arrangement of the river with its tributaries from the source to the mouth. Therefore the concept drainage includes rivers , swamps, lakes, waterfalls ,flood areas
The drainage pattern: refers to the arrangement of river and its tributaries in relation to geological structures.
Types of drainage patterns
1. Dendritic drainage: Is the drainage pattern which look like tree branches. It is formed in areas with uniform rock structure where by the tributaries join the main river at the acute angles.
2. Trellised drainage pattern: Is the drainage pattern found on areas with different rock structures. Therefore under this type of drainage pattern the tributaries join the main river at the angle of almost 90 degrees angles.
3. Radial drainage pattern: Is the drainage pattern in which tributaries flow outward from the center. It is normally develop in area with volcanic dome.
4. Centripetal drainage pattern: this is the drainage pattern in which almost all streams are flowing towards the center which can be to the swamp, lake or depression.
IDENTIFICATION OF ROCK TYPES ON THE MAP
Rocks: Refers to the aggregate of minerals in a solid state. surface rock on the topographical maps is not directly indicated but there are some guideline to consider when one decribe the type of rocks.
MAJOR TYPES OF ROCKS
1. Igneous rocks.
2. Sedimentary rocks.
3. Metamorphic rocks.
TYPES OF ROCK IN RELATION TO PHYSICAL FEATURES
METHODS USED TO IDENTIFY ROCK TYPES
1. Land forms
i. The presence of volcanic land form such a crater, caldera, name of the volcanic mountains suggest the presence of igneous rock.
ii. Presence of erosion and depositional features on the map such as depression, sand dunes, coral reef suggest the presence of sedimentary rock.
iii. Flood plain suggest sedimentary rock.
iv. Presence of folds on the map indicate metamorphic rocks.
v. Presence of highland with steep slope indicated that rock are hard and resistance to the erosion. Hence such hard rock can be granite quartzite and gabbros.
v. presence of gentle slope, indicate soft rock e.g. sedimentary rock
2. Vegetaions.
i. Dense forest indicate the presence of igneous rocks.
ii. Poor vegetation cover suggests the presence of sedimentary rocks or metamorphic rock.
3. Water bodies
i. Absence of streams: indicates that the rocks are permeable rocks. that the rock is soft which can either be sedimentary, limestone or sandstone.
ii. presence rivers, lake, seasonal swamps or ocean: indicate presence of sedimentary rocks.
4. By using drainage patterns.
i. Presence of dendritic drainage pattern indicate Igneous rocks.
ii. Presence of Trellis drainage pattern indicate metamorphic rocks.
iii. Presence of radial drainage pattern indicate Igneous rocks.
iv. Sentripetal drainage pattern indicate Sedimentary rocks.
INTERPRETATION OF VEGATATION DISTRIBUTION ON THETOPOGRAPHICAL MAP
Vegetation refers to the total assemblage of plant covers in an area. Topographical map shows vegetation with reflection to actual areas represented.
Types of vegetation found on the map
a. Natural vegetations.
b. Artificial vegetation.
1. Natural vegetation: These are vegetations which are free from human influence. Are natural occuring vegetation on the earth surface. The forms of natural vegetation which can be observed from the topographical maps include the following:-
i. 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.
ii. Woodland: The type vegetation formed by less closely spaced shorter trees. These grow in areas of moderately high rainfall.
iii. Thicket: This type of vegetation is of dense shrubs and scattered low trees and commonly found in region of moderately seasonal rain.
iv. Mangrove: These are the salty trees found in areas along the shores of coasts line.
v. Scrubs: The vegetation of much low lying trees commonly found in areas of long dry season.
vi. Scattered trees: These are the vegetation of widely spaced trees. These also commonly found in areas of seasonal rainfall.
vii. Planted vegetation: These are more particularly of the cultivated plants (crops) like sisal, tea, coffee, and scattered cultivation.
VEGETATION DISTRIBUTION ON THE MAP
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.
Factors influencing vegetation distribution on the map.
There are several factors that may influence vegetation distribution. These are
i. 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.
ii. 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.
iii. 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.
iv. 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.
INTERPRETATION OF LAND USE ON MAPS
1. Agricultural land use: This is presented by large-scale commercial cultivation and also small scale holders.
2. Recreational land use: These may be natural reserves, national parks, skirting ground, playing fields or cemetery.
3. Industrial land use: These are presented by factors for location of industries such as power line, raw material and others.
4. Waste lands: These are areas of very high relief and gorges not useful for any economic activities.
5. Residential land use: If the topographical map show huts houses, building, towns etc.
INTERPRETATION OF CLIMATE ON THE TOPOGRAPHICAL MAP
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:
i. 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.
ii. 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
i. 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.
ii. 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
i. 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.
ii. Presence of abundant permanent streams and permanent swamps, suggests heavy rainfall received in the area.
iii. 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)
i. Presence of thick forests in a map indicates heavy rainfall.
ii. Woodland vegetation indicates moderate rainfall.
iii. Scrubs, thickets and grassland indicate dry condition. Examples (crops)
i. Presence of cotton, sisal and cashew nuts suggest moderately high seasonal rainfall and high temperature.
ii. Presence of coffee and tea on the map and up on the area represented, suggest cool wet climate.
INTERPRETING HEMISPHERE ON THE MAP
Normally in the globe, hemisphere is divided into:-
i. The southern hemisphere: is located at south toward the South Pole.
ii. The Northern hemisphere: and northern hemisphere is located at north toward North Pole.
To interpret the hemisphere in which the mapped area is located, the most important thing to consider is to determine the number of latitude line and symbol.
Hemisphere varies consideration from one natural region to another. It is thus; if the number of latitude line ending with the later S, this letter means southern hemisphere and also if the number ending with the letter N, this letter means northern hemisphere. So the hemisphere is recognized by taking into consideration of the latitudes indicated along 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.
INTERPRETATION 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 include:-
i. Roads: These are of the varied nature and include the following
a). All weather roads bound surface: These are tarmac roads. These normally used throughout the year including during the rainy season.
b). All weather road loose surfaces: These are the roads whose surface covered in murram. These also can be used throughout the year.
c). Dry weather road: These also covered in murram but they are only reliable in dry season.
d). Motor cable tracks: These do not fall in the category of roads, but they can be used by motor vehicles especially in dry season
ii. Footpath: These are the ways through which people move from one area to another on foot.
iii. 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:-
a). Main railway lines: These on the topographical maps represented by the black shading which alternate with white ones.
b). 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.
INTERPRETATION 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:-
SETTLEMENTS
Settlement: Is theplace where people live and conduct their social and economic activities by interacting witth environment.
Major types of settlement
There are two types of settlements which commonly than on the topographic of a map and these includes, rural and urban settlement.
1. URBAN SETTLEMENT
Is commonly found I areas of the following nature. District administrative centers Regional administrative centers
Capital city of a country.
2. RURAL SETTLEMENT
Is an area with low number of people which approximately to cover about 80%.
SETTLEMENT PATTERNS
Settlements pattern: refers yo the arrangement of settlement. Types of settlement pattern
QN: Describe the nature of settlement pattern on the maped area.
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:-
i. Scattered cultivation.
ii. Individuals farms are large enough and population is too sparse
iii. Pastoral society
iv. 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:-
i. Urban area where people more concentrated
ii. Planned villages
iii. The presence of economic factor like industrial factor
iv. 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.
FACTORS INFLUENCING SETTLEMENT DISTRIBUTION ON THE MAP
1. Availability of accessible water supply: A source of fresh water such as river, lake, dam, oasis or a well usually attract settlement because many activities both domestic and industrial use water. Most urban settlement have been growing due to availability of clean water particularly tape water.
2. Social facilities: Settlements tend to be concentrated in those areas where social facilities such as education, religious, health and piped water exist. These areas are characterized with a large concentration of dot.
3. Economic activities: Economic activities such as agriculture, mining, trade industries also attract settlement. The fertile soils particularly in highlands have attracted a good number of people in east Africa.
4. Relief/topography: Settlement is limited in lowlands that are prone to floods and other related problems such as poor drainage. The dots representing population on maps are widely spaced. Mountainous and hilly areas with steep slopes are also avoided as they are inhabitable. On gentle slope that are properly drained the distribution of settlements is usually dense. Such areas on maps are characterized by dense dots.
5. Administrative function: Administrative activities in areas like capital cities, district headquarters and important towns also attract settlement as most people are employed in these administrative centers including state house, government ministries and so on.
6. Transport and communication: Transport routes especially roads attract settlement alongside them. Settlements usually come up along the newly constructed roads and railways to form linear settlement.
INTERPRETATION OF POPULATION DISTRIBUTION
Population refers to the total number of people living together in a certain geographical area. Population distributions refer to the spread of people in a 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 has medium density and areas have high density population. This is due to the following factors
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
INTERPRETATION OF HUMAN ACTIVITIES
Human activities 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.
INTERPRETATION OF ECONOMIC ACTIVITIES ON THE TOPOGRAPHICAL MAP
Economic activities are the ones conducted by people for purpose of earning livelihood. These are for income earning to improve economic growth of an individual or society as whole. Topographical map have much to tell about the ways in which man feeds and earns his livelihood. Economic activities on the topographical map can be identified as follow:-
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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.
IDENTIFICATION SOCIAL ACTIVITIES ON THE TOPOGRAPHICAL MAP
Social activities include the ones conducted to meet social motivation like education, medical care, security, entertainment and others. The identification of these activities from the topographical map is as follows.
1. Health services: This can be indicated by the presence of hospitals and dispensaries.
2. Education services: This can be suggested by the presence of schools, college and universities.
3. Religion/worship services: This also can be indicated on the map by the presence of church and mosque.
4. Security services: This also can be indicated on the map by the presence of army camp, police office.
5. Administrative services: This also can be suggested on the map by the presence of DC office, RC office, PO etc.
6. Transport and communication: This also can be indicated on the map by the presence of road, railway, telephone line and other means of transport.
7. Entertainment: Is indicated by the presence of clubs, rest house, hotels, motels, and others also reveal the same.
FUNCTIONS OF TOWN ON THE TOPOGRAPHICAL MAP
1. Trading functions: Some towns are trading center indicated by the presence of sores, roads, shops and market.
2. Administrative function: Other towns may be administrative centers suggested by the presence of police posts, D.C office, D.O office, court houses etc.
3. Educational functions: They can be educational centers indicated by the presence of school or colleges.
4. Transport functions: 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.
5. Health functions: They can be health centers indicated by the presence of hospitals and dispensaries.
6. Industrial functions: Others are industrial centers indicated by the presence of factories.
7. Agricultural function: Some towns are agricultural centers evidenced by the presence of sores, depots etc.
8. Cultural functions: Town may be cultural center indicated by the presence of theaters
9. Mining functions: The may be mining centers suggested by the presence of quarries, mineral work, mines.
IDENTIFICATION OF HUMAN ACTIVITIES/ LAND USE ON THE MAP
Topographical map may contain information on economic activities undertaking usually the following are shown on topo maps.
ECONOMIC ACTIVITIES
1. Agriculture: It indicated by presence of, Rural settlement in absence of other activities, scattered cultivation, storage houses/center, plantation or estate (indicate large scale agr), industry such as Ginneres, Hulleries and Decotecator
2. Pastoralism: It indicated by the presence of, cattle market-cattle dips, veterinary installation (Vet. Office)/center, Creamers (lace where milk, cream butter and cheese are processed, Scattered vegetation or dominated by scrub/shrubs), Bore holes (Bore holes (BH) or water hole (wh)
3. mining: It indicated look on the presence of, symbols of PIC and shovel, salt work, quarrying, Roasting, Sign Tin-TN, Iron-Fe.
4. Fishing: It indicated by the presence of water bodies such as lakes, seasonal swamps, rivers, dams, ocean. These should be surrounded by settlement.
5. Trade and transportation: Look on the presence of road, railway, towns and market
6. Lumbering: It indicated by the presence of forest with track-roads ending to the forests, Saw-mill, Sao hill forest.
7. Tourism: It indicated by the presence of, National parks, Game reserve, Recreational centre’s e.g. museum, archives beaches etc.
SOCIAL HUMAN ACTIVITIES/ AMENITIES
1. Education services: it indicated by the presence of school, colleges, etc.
2. Water supply: it indicated by the presence of water pipes lines.
3. Health services: it indicated by the presence of hospitals, dispensaries, etc.
4. Security services: it indicated by presence of police station, military camps, coarts, prisons, etc.
5. Religious services: it indicated by the presence of mosques, churchies.
GUIDING QUESTIONS
1. Describe five limitations of using map on geographical studies.
2. Determine the nature of rocks/ geology on the map.
3. With evidences describe the nature of geology.
4. By giving evidences in three points describe factors which makes this map to be unique from other maps?
5. With evidences from the map describe three contents found on the map.
6. Outline five map supportive content/marginal informations found on this map.
7. By giving evidence outline four factors which distinguish this map from other topographical maps.
8. Describe the relief of the mapped area.
9. Determine the type of climate on the map.
10. Describe in four points how can you identify the nature of rocks on the topographical map?
11. By means of supportive evidences, describe the nature of vegetation distribution on the map.
12. Give four reasons for uneven distribution of vegetation on the mapped area.
13. Given the nature of plant cover observed on the map.
14. Outline relief features found on the map.
