Monday, August 22, 2022

GEOGRAPHY FORM 5 TOPOGRAPHICAL MAP INTERPRETATION-INTRODUCTION TO A MAP

GEOGRAPHY FORM 5 TOPOGRAPHICAL MAP INTERPRETATION-INTRODUCTION TO A MAP

GEOGRAPHY FORM 5 TOPOGRAPHICAL MAP INTERPRETATION-INTRODUCTION TO A MAP
Monday, August 22, 2022

GEOGRAPHY FORM 5 TOPOGRAPHICAL MAP INTERPRETATION-INTRODUCTION TO A MAP

UNAWEZA JIPATIA NOTES ZETU KWA KUCHANGIA KIASI KIDOGO KABISA:PIGA SIMU: 0787237719




ALSO READ;

  1. O’ Level Study Notes All Subjects
  2. A’ Level Study Notes All Subjects
  3. Pats Papers

TOPOGRAPHICAL MAP INTERPRETATION-INTRODUCTION TO A MAP

INTRODUCTION TO A MAP

What is a map?

Map is a scaled conventional representation of the whole or any of the earth’s surface on a flat body.

Or

A scaled conventional visual representation usually on a plane surface of a region of the earth.

Flat body into which maps, established include, a piece of paper , blackboard, wall, wood, cloth and others of the same consideration.

Maps are the most valuable and powerful equipments in Geography as used for providing geographical details of varied areas represented. They are geographical details of varied areas represented. They are also used for storing the geographical details of areas represented. Some of the geographical facts which can to depicted by maps about areas represented include; climate, relief, human activities, soils, drainage system, vegetation, settlement, settlements, communication and others of similar consideration. It is thus; maps are so useful for making geographical facts description about the respective areas represented. Other useful tools apart from maps which also enhance geographical studies; graphs, globes, globes, ground photographs, aerial photographs and the satellite images.

CATEGORIES OF MAPS

Maps used in geographical studies are extremely varied and belong to different forms. They are classified by considering the following categorizing factors.

  • heir varied functions
  • Scale size used
  • The degree of accuracy




Maps according to functions

Classification by function, it is taken into consideration of what a particular map shows. Maps portray varied geographical facts and thus are of different functions depending on what shown. With respect to this, map are broadly categorized into four and include the following.

(a) Topographical maps

(b) thematic maps

(c) Statistical maps

(d) Cadastral maps

 

TOPOGRAPHICAL MAPS.

The maps are named with the world ‘topography’ which has been derived from a Greek world of ‘Topos’ The word topos means the actual appearance of a place by its natural and artificial features.

Or
. The map which has been designed to give a general future (description) of the landscape of a very limited part of a country by showing both natural and artificial features.

Or
Map whose principle purpose is to portray and identify the features of the earth’s surface as faithfully as possible with in the limitation imposed by scale.

Topographical maps considerably to their future of function are also known as general maps.

 

Characteristics of topographical maps

  •   Show both natural and artificial features of areas represented.
  •   They are drawn on their medium or large scale depending on the size of the area represented.
  •   Represent small or limited parts of a country
  •  They are more detailed as represents small parts on large scale.

Thematic maps

These are the special maps which concentrate on showing the spatial distribution of a single geographical phenomena among the several of areas represented.

Or

Types of map especially designed to show particular theme connected with specific geographical areas. i.e. they show the distribution of only one geographical fact among the several of a particular region. These can portray physical, social, political, economic, or any other espects of a city, state, region, continent and world at large.



Thematic maps are differently named according to the nature of content (details) of an area represented and include the following:-

  • Relief maps:- These show the physical appearance of areas represented by giving the major land forms.
  • Political maps:- They show political boundaries of administrative for regions represented.
  • Geological maps: The maps concentrate on showing the geological nature for the regions represented.
  • Soil maps: The ones which show the spartial variation of soil nature for areas represented.
  • Economic maps: These show the spatial distribution of chiefs crops, animals, industries, minerals and others.
  • Historical maps: show the distribution of the historical sites.

Statistical maps.

These are the geographical maps which show the distribution of certain geographical phenomena in values of phenomena of interest in geographical studies lie temperature, population density, movement of goods or people and others of related. With the use of statical maps, one can make quantitative analysis of a phenomena for the area shown on the map.

Statistical maps are further differentiated by considering the means used to show the values of distribution on the map face. Owning to the consideration, statistical maps include the following:-

Isopleths maps.

These statistical maps which show the distribution of a certain geographical phenomena in quantitative manner by of lines. The lines are established on a map face to join points with equal amount of distribution with reflection to an actual area on the earth’s represented.

The used lines have special names depending on a nature of phenomena shown on the map.

  •  Isohyets: for rain fall
  •  Isotherms: for temperature
  •  Isobars: for atmospheric pressure
  •  Isohaline: for salinity
  •  Isobaths: for ocean depth


Dot maps.

Such statistical maps designed to show values on spatial distribution of a certain geographical phenomena by means of fixed size dots as inserted on a map face. Each dot on the map carries equal values similarly to others.

 

Choropleth maps.
These statical maps are designed to show values on the distribution density of a certain geographical phenomena like that of population by means of varied shade texture. The map is established to have a key to interpret the categories of quantitative values represented by the varied shades.

 

Flow line maps:

These are designed to show the quantitative values on movement of certain geographical phenomena like passengers or goods from one place to another through an established route way of like: a d, railway, water way and others by means of flow lines of varied width. i.e. the amount on movement reflected by the width of the flow lines.




Cadastral maps

They are the maps of large scale which show more Clearly the layout and boundaries of features of a very small size represented. i.e. The maps show precise locations and names of the features of the area represented.

Cadastral maps are mostly designed for ownership purpose. These maps may show the layout of features in a village, part of a town, industrial area, school compound, home steady and others of the same reflection.

Cadastral maps are commonly designed after the boundaries of the features in the area to have been accurately surveyed. The type of survey that concentrates on taking the actual measurements of features boundaries is known as cadastral survey. It is thus the maps are named in basis of the technique used to get details that appear on the map.

Maps according to scale size.

Maps being much smaller in size compared to actual areas represented, are precisely designed up on distances to grounds represented. However the maps size of the ground and amount of details shown, Being drawn up on varied scale size, makes maps appear extremely varied and this becomes another important categorizing factor of maps. It is thus, maps according to scale size categorized into the following types.

  • Large scale maps
  • Small scale maps
  • Medium scale maps

 

Large scale maps.

These are drawn on large size to give larger representation of limited parts of a country like a town or village. These commonly established on large spaces of flat bodies.

Characteristics of large scale maps

  •  They are drawn on large scale size e.g. 1:10,000, 1:20,000 etc.
  •  The maps give larger representation of areas portrayed.
  •  They represent very limited parts of the country
  •  They are more detailed.

 

Small scale maps.

These are the geographical maps drawn on small scale representing larger area size of the earth’s space of the body.

 

Characteristics of small scale maps:

  • They are drawn on small scale e.g. 1:1,000,000, 1:10,000,000 etc.
  •  The maps give smaller representation of the areas of the earth’s surface.
  •  They commonly represent very huge parts of the earth’s surface like a country, continent or the whole of the earth’s surface.
  •  The maps are more selective and thus, show less details of represented due to the limitation of map space.




Medium scale maps.

These are the maps drawn on medium scale size to represent parts of the earth’s surface.

 

Characteristics of the medium scale maps

  • They are drawn on the medium scale size E.g. 1:100,000,1:25,000,1:150,000 and others of the same consideration.
  •  Both the map and ground represented are of medium size.
  •  The maps show moderate level of details.

 

Maps according to degree of accuracy.

Cartographers try to their level best to make maps most accurate in order to reflect the reality of areas portrayed. They employ varied techniques to make maps be of reasonable accuracy, However, with respect to this consideration, some maps are made accurate, while others not accurate and thus: maps differ in the degree of accuracy and this also taken as maps according to the degree of accuracy broadly classified into two types and include:

  • Outline maps
  • Accurate maps

 

Outline maps.

These are the simple maps which not accurately designed as drawn not up on scale. They are commonly shown in text books to make simple illustration of the geographical facts. Moreover, they are commonly printed or copied for personal or classroom uses.

 

 Accurate maps.

These are the ones which have been precisely designed as drawn with the use of correct measurements of the area, its features as well as the map itself. i.e. the maps accurately designed with up on scale. Commonly on the map, the represented area and the features made to have correct size.

Accurate maps are subdivided into two depending up on the technology used o maintain the accuracy.

 

Surveyed maps.

These are the maps made accurate taken by actual measurements on distance, area represented. Most of the topographical maps correspond to this category.

 

 Project maps

These are the maps which show the accuracy of the earth’s surface curvature (spherical shape) on their faces maintained by the cartographic technique of projection.

 

  USEFULNESS OF MAPS

  • Maps provide good basis for making orderly geographical facts description of regions represented. i.e. The geographical facts of an area such relief, drainage, settlement, communication,vegetation and others easily recognized and described from the topographical map.
  • They provide ideal insight  into significant relationship  between geographical f variables. I.e. They are considered to establish the relationship between the geographical variables . E.g and soil,relief and vegetation, climate and vegetation etc.
  • In connection to above point, maps are so powerful tools for making spatial analysis of geographical facts for areas represented. i.e. from map , the determinant factors for spatial  variation   of geographical phenomena detected.
  • They are so potential for field studies.
  • Maps are useful for traveling purpose. They guide people to reach points of designation·     Maps are useful for locating the position of geographical features .It is achieved by a wide range  of methods mostly, grid reference, place naming the use of latitudes and longitudes bearing and distance.
  • Maps make storage of the geographical facts of areas represented. Hence the give insight to the previous appearance of areas.
  • Maps can be used to make quantitative analysis of certain geographical facts like size, distance, gradient, drainage density in response to scale consideration.
  • Maps are used for military purpose. i.e. they used to develop military strategies by providing vital details to military troops.
  • Maps are used in the conduct of a wide range of projects like: population census, land use planning, building design, construction of roads and others of the same reflection.




SET BACKS OF USING MAPS.

  • Maps are convention, and thus do not give the morphology of features represented. Features on maps appear by means of convention signs, symbols and abbreviations.
  • Maps are selective. It is not possible for all details to appear on the map. Hence: with the use of maps in geographical studies, we lack some of the details.
  • The features shown on the maps may not be all maintained on a constant scale. It is thus, uses may get distorted measurements of the features from the map.
  • Maps may provide the outdated details about the respective areas represented. It is automatically set as details in actual areas may change with time while maps once designed remain unchanged.    Moreover, it becomes difficult to update the map that has already been designed.
  • The reading and interpretation of maps needs high and perfect skill.
  • Maps are not capable to record and keep instant data

EXERCISE

Qn. Briefly explain any five merits of such topographical map to a map user (NECTA 2000 – The extract map of madukani series 742)

Qn. Outline the strengths and weakness of using topographical maps in geographical studies. Mock –

CONTENT OF MAPS

Map content refers to a body of information inserted on a map with reflection to the actual area represented. i.e. the details shown on a map which reflect the nature of the area represented or what generally contained on the map.’

The content established on topographical maps are so varied and thus ; classified into three categories of the following:-

  • Natural contents:-The features which are distinctive from man made. They include: relief features, drainage features, vegetation features and others.
  • Artificial contents: These are considerably to the features of man made such as cemetery, roads, railways, settlements, airfield and others of the same reflection.
  • Supportive contents: These are the marginal details established to make well defined. Some of the supportive details include: scale, heading, key, date of compilation, northern  direction  and others of the same reflection.

 

FACTORS WHICH DETERMINE CONTENT OF MAPS

Most of the maps do not show (have) similar content i.e. details are considerably varied from map to maps. For instance: a map of Africa observed to show political boundaries of the countries, while the other shown physical appearance of the continent. Moreover: a map may appers more detailed; while the concluded that, variation of details on maps occurs as functioned by certain of details on maps occurs as include the following:-

  • Objectivity of the map drawn
  •  Scale size of the map used
  •  Date of compilation
  •  The nature of the area represented
  •  The nationality of the cartographer

1.Objective of the map drawn

This largely depends on the aim of the cartographer (map maker). Usually maps are selective as it is difficult for all surface details to appear the map. Hence any map reflects its purpose.

2.Scale size of a map used

Maps are drawn on varied scale size depending on the size of the ground and size of the map it self. It has to be taken into consideration that, scale size of a map is what determines the amount of details of an area to be shown on the map, in common, a map drawn on a small scale is made to have limited space and less details would have been shown on it. Conversely to a map drawn on large scale , is made to have large space and very possible to display a lot about the represented area.

3.Date of compilation

Date of compilation refers to a period of time when a map was designed. It has to be taken into consideration that, land details are dynamic over time. With respect to this, a map is likely to show details which were present by the time of its designation. It is likely to have variation in details.

4.The nature of the represented area

A map shows what is found in the represented area and not otherwise. Therefore, maps which details.It is thus, a map reflects the reality of the area represented.

5.Nationality of the cartographer.

A map to represent part of the earth’s surface can be constructed by the foreigner or local cartographer. The two maps may differ in content due to the fact that, the foreigner cartographer might not to include some surface details because of being not familiar with the area. Moreover the foreigner cartographer may misname the places on the map of the region represented.

 

EXERCISE

Q. (a) What factors affect the content of topographical map?

(b) Classify the features that are commonly shown on topographical maps. (NECTA 1991)

Q. Explain the factors that affect that affect the content of topographical maps. (NECTA 2008)

CARTOGRAPHY

Cartography is an art or a science of designing a map to represent either the whole or any part of the earth’s surface in scaled and conventional form.

There are noticeable contrasts between maps and the whole or parts of the earth’s surface represented as follow:-

·Map is flat, while the earth’s surface or part of the earth’s surface is not flat.

·  Maps are much smaller in size, while the whole earth or a part of the earth represented is much larger in size.

With this the map makers use a cartographic technique to maintain the accuracy of the earth’s shape and size on maps. The technique is known as map projection. It is thus; the cartographic technique is associated with map projection. It is thus; the cartographic technique is associated with map projection as a sole means of maintaining accuracy of areas on maps.




MAP PROJECTION

The earth’s surface can be wholly represented with reasonable accuracy on a globe. But globes are not as convenient as flat maps to use. Globe can not depicts much details like transportation system of a city, or the location of very small towns or villages. With this, maps have to be produced to facilitate geographical studies.

To make the maps so accurate, a cartographic technique of map projection is defined as the cartographic technique of transforming the shape of the earth’s surface or part of the earth’s surface more accurately to a plane surface to develop a map that can be easily worked with less distortion. i.e. It is the cartographic technique of maintaining the accuracy of an area on a map.

The cartographic technique of map projection is recognized be of varied types as flat bodies into which maps developed differently projected. This develops cylindrical, conical and plane map projections

The cartographic technique of map projection is recognized be of varied types as flat bodies onto which maps developed differently projected. This develops cylindrical,conical and plane map projections. More over;on a map, the features are made to have accuracy on different respects. This also develops the types of azimuthal, gnomic and stereo graphic map projections.

Cylindrical projection

By cylindrical projection, the shape of the earth’s surface is accurately maintained as a frat body onto which a map would be drawn, projected to a shape of the earth’s surface is maintained and then the cylindrical projected body is cut to develop flat map onto which the whole earth surface appears.

Cylindrical projection is alternatively known as mercators projection.

 

Conical projection

It is a considerable form of map projection, by which, the shape of the earth’s surface is accurately maintained as a flat body onto which a map would be drawn is projected to a conical shape. Over the surface of projected conical body, the shape of the earth’s surface is maintained then the conical body is cut to develop a flat map onto which the whole earth’s surface or part of the earth surface appears.

 

Plane projection

By plane projection, the area particularly of a limited size whose accuracy is directly maintained on a flat body os a piece of paper.

Azimuthal projection

It is a type of map projection which mostly used to maintain the correct distribution of the surface features on a map by being maintained in true directons and distance relatively to one another with reference from the centre of a map and up on the actual area on the earth’s surface. By this, all bearings are laid off correctly from the central point of the map, so that all points on the map and up on the area on the earth’s surface are true in distance and direction from the centre.

Gnomic projection

It is alternatively known as equi-distance projection. This is used to maintain the accuracy of ground distances on the map with respect to the used scale by regarding the relative bearing of the features in the area.

Streographic projection

It is a cartographic technique of preserving the correct shape of earth’s surface features on a map. Preservation of the features is maintained by taking into consideration of the satellite images and aerial photographs.

FACTORS INFLUENCING CARTOGRAPHIC PROCESS

(KEY ISSUE CONSIDERED IN MAP MAKING)

I n a process of map making a present a certain part of the earth’s surface, the following should be taken into consideration as guides to map maker.

  • The size of the actual area to be represented on a map. The size of the area is revealed by making survey or by examining the vertical photograph that represents the same area.
  • Size of the plane surface of a piece of paper onto which a map would be designed.
  • ·Map scale. The scale is determined by relating the corresponding distance between the map and ground. Scale is what determines the amount of details about the area appear on the a map.
  • Methods of projection as means of maintaining the accuracy of the map.
  • Nature and amount of the features to be shown on a map. This largely depends on a type of map would be designed under plan and chosen scale size.




PROCEDURE IN MAP MAKING

The construction of a map involves the following important steps:-

(a) the cartographer has to make overall plan of a kind of map to be designed. The plan depends on what is intended to appear on the map about the area. i.e. the plan can be design : topographical map[, statistical map, thematic map or cadastral map.

(b) Collection of data from the area to be mapped. The nature of data to be collected depends on a type of map to be prepared. For instance; if the plan is to prepare a topographical map, the cartographer would have to collect the general geographical details of both natural and artificial features present in the area.

 

Data can be collected by involving the following methods.

·  Making of the field survey in the area.

· By examining the respective vertical aerial photographs.

·  By examining the respective satellite images.

·  Data can be delivered from the existing sources like books and other maps.

(c) Choice of a scale. This has to take into consideration of both, size of the flat body of a sheet of paper and the size of the ground to be mapped. The scale is determined by relating the corresponding measurements on distance between the map and ground.

(d) Representation of the data or details on the map. The data can be represented by means of the conventional symbols, varied colours, varied shade textures, writing the names of features or places and other important means.

(e) the map should be given with the supportive details to make it well defined. These include; title, key, north directions, scale, date of compilation and others of the same importance.

 

LIMITATIONS IN MAP MAKING.

(a) Determination of the map scale; by relating the corresponding distances between the map and ground. The uses scale might have been assessed by using wrong measurements between the map and ground. For instance; the surveyed ground distance to be related to map distance might have been subjected to errors accumulation.

 

(b) Difficulties in cartographic representation. It is much based to the representation of the features on a map. The problem a rise on the following.

·   What to be shown on a map regarding that, a map is selective in nature. i.e. It is more difficult to make all details appear on a map.

·  Representation of the data of the map by inserting the name of the features, conventional signs and symbols, colors and shades. All these require high skill.

·  Dynamism problem. Areas mapped subjected to changes. This makes maps appear outdated. Moreover; it becomes much difficult to update the map.

·   It becomes much difficult for all features maintained on a constant scale of the map.

 

(c) Human problems

(i) technology

The designing of maps requires higher technology. This makes most of the maps designed manually and become not exactly accurate.

 

(ii) Financial problems

The making of a map is a expensive process. This makes maps not recurrently produced.

 

(iv)Poor communication

This greatly hinders the process of data collection in areas that would be mapped.

 

EXERCISE

Q. Write briefs notes on map projection (DSM – Mock 2003)

Q.

(a) Differentiate between thematic and topographical maps.

(b) Outline the problems encountered in a process of map making. MOCK – Qn.)




ESSENTIAL OF MAP

These are the supportive details given on a map to make it well defined with reflection to an actual area on the earth’s surface represented. Such details make the map well understood and interpreted to recognize clearly the geographical facts of the area represented. The are usually given on the map border. Absence of these on the map, makes difficulties in map reading and interpretation.

 

The main essentials of maps include the following.

 

(1) Title

It is a heading of a map designed. The significance of it is to tell what the map is for about. This is commonly indicated at the top of the map; and on other maps appear at bottom.

Map title is of two forms depending on what the map shows and include:-

General title

It is given to a map that shows the general geographical details of an area represented. It is established by writing only the name of a region represented. This form of title commonly appears on a topographical map. E.g. MOROGORO.

Specific title,

This is made to appear on a map that shows specific content among of the several about the represented area. Specific title mostly appears on thematic and statistical maps. E.g. MOROGORO LAND TRANSPORT LAYOUT.

 

(2) Key

It is the list of all conventional symbol, signs and abbreviations together with their meaning on the map border. Maps are conventional in nature as represent land features by means of conventional symbols, signs and initials or abbreviations. It is therefore significantly potential, in order to make a map well defined and understood, it should be established with a key to show what the conventionas symbols, signs and abbreviations or initials stand for.

 

(3) Scale

A map is much smaller in size compared to the actual area represented which is much larger in size. It is thus, maps are accurately designed up on scales.

It is therefore important for the used to appear on a map in such a way map user may take into consideration of it for futher assessment.

Scale on a map enables the users to understand the relation ship of distance to ground, which then helps to understand the bigness of the area represented and other ground measurements of interest like distance and gradient.

 

Scale on the map is expressed in three varied ways and these include:-

·   In representative fraction. E.g. 1;50,000

·   In statement (verbal expression) eg, 1 cm on a map represents 2kms on the ground.

·  Graphically; e.g.

 

(4) Indication of north direction

Any map should be indicate with north direction. On topographical map is commonly indicated by the following conventional sign.

The significance of north direction indication on a map is to enable the map uses to recognize readily the north direction and other important directions of like; North west, East, North east etc, of the represented area. Beside to this; the indicated north helps and features on the map and up on the respective area represented on the earth’s surface.

It has to bear in mind that, bearing of an observation line between two points is measured clockwise from north direction of 0000

(5) Margins

It is the frame work of the map designed. The role of a margin is to show the end of the represented area; and also makes the map impressive and attractive to the users.

(6) Date of compilation.

It is a date of map publication. It is very important for a date of compilation to appear on map. The enables the users to realize the following:-

·    Whether the map is updating or outdated relatively to the actual appearance of the respective area represented.

·  The changes which have occurred in the area. This can be realized by comparing the latest map to other maps or the given map to the current appearance of the area.

·     To calculate magnetic variation of a place by taking into consideration of the rate of changes per annum. Be side to this, it may also help to calculate the new magnetic bearing of an observation line from a place to another place.

(7) Grid lines and latitudes and longitudes.

Grid lines are the vertical and horizontal lines drawn on a map face crossing at right angles giving so perfect squares. The lines are numbered to make eastings and northing.

Latitudes and longitudes are the imaginary angular distance lines drawn on the face of map and given with the degree numbers as have been measured more accurately from the centre of the earth’s surface. These represent the angular distance of the area on the earth’s surface from the centre.

Grid lines, latitudes and longitudes in general, have a potential significance of enabling people using map to locate position of geographical features on the map with reflection to actual areas represented.

Moreover; the latitudes and longitudes enable map mapped areas from the centre of the earth.

Note.

The grid lines are commonly established in more details on large scaled maps as they represent small areas. While, the latitudes and longitudes are widely printed on small scaled maps as they represent wider parts of the earth’s surface.

(8) Map identification details.

These included both; serial number and sheet number of the map. The are potentially significant in recognizing easily the maps and also make clear distinction map to maps.

(9) Publisher and copy writer owner.

It is important that, to any map the name of the cartographer or institution constructed the map has to appear. This may help the map users to make necessary consultation with the cartographer or institution constructed the map has to appear. This may help the map users to make necessary consultation with the cartographer or institution to have more clear details about the area which has been mapped.





 MAP SCALE

Maps are all generally, much smaller in size as it an be compared to the actual areas represented which are much larger in size. Hence; a map scale is a relationship of map distance to ground represented. This is what understood as map scale. It is thus ; map scale defined as the constant relationship between the shorter lengths on the map and larger ground distances represented.

Or

The ratio of distance between the map and the actual ground represented and the fundamental application for this is as follows:-

 

Map scale  =     Map distanceGround distance

 

CATEGORIES OF MAP SCALES

Scales of maps are not all the same. They are extremely varied in size, expression methods and units of corresponding distance expression. It is thus; map scale are classified according to such terms of variation.

 

MAP SCALES ACCORDING TO SIZE.

Large scale :-

It is a type of scale which gives larger representation on a map and permits limited details to appear.

Small scale:-
This makes smaller representation of very wider part of the earth’s surface on a map permit limited details to appear.

 

Medium scale:-

This provides a medium representation of a part of the earth’s surface on a map and permits details in moderate level to appear.

 

There is no general agreement of the quantitative limits of the terms, small, large and medium scales. However most of the cartographers agree that:-

  •  A map with reduction ratio 1;50,000 or less would be large e.g. 1:25,000
  •  A map with reduction ratio of 1:500,000 or more is considered as small scale e.g. 1:1,000,000.
  •  A map with reduction ratio of in between of the two above, considered medium scale. E. g. 1:200,000. 


Scales according to the forms of expression.

It is widely considered on how a scale has been indicated on the map. This generates three types of scales and include the following.

Statement scale.

This is also known as verbal scale. It is considerably to a scale that is expressed on a map by being stated in words. E.g. 1 cm on a map represents 1 km on the ground.

Representative fraction scale:-

It is considerably to a expressed on a map in ratio or fraction with numerator and denominator appearing in a similar smaller unit e.g. 1:50,000

Linear scale.

This shows the ratio of distance between the map and ground along the line.

Map scales according to expression units used

Scale according to this consideration, broadly categorized into two and include the following.

 

Metric scale.

It is a scale system in which the units of expression for the corresponding distances between the map and ground are of metric e. e. 1 cm represents 5km.

Imperial scale:-

It is scale system in which the units of the corresponding distances between the map and ground are of imperial. E.g. 1 inbch represents 2.5 miles.

 SCALE SIZE OF MAPS

Scale size varies considerably from map to maps as some drawn on large scale, while others may be drawn on medium or small scale. Variation in map scale size is made by some determinant factors.

The main determinant factors for map scale size include:-

  • Size of the ground represented by the map
  • The size of the map drawn
  • Amount of the ground details shown on the map


Size of the ground represented.

Maps which represent varied grounds in size differ in scale size. Smaller ground is made have larger representation on a map and thus; the map is subjected to have large scale. Conversely; wider area is made to have smaller representation and thus; the map subjected to small scale.

Map A; is of large scale as the represented area is smaller in size; while map B is of small scale as much wider area represented.




2. Size of the map.

Maps of varies size differ in scale size. A map of large size makes large representation of an area and thus, subjected to large scale size. Conversely to a map of small size makes smaller representation of an area and thus; subjected to small scale.

3. Amount of details.

This controls scale size indirectly. Maps constructed to show varied levels of details differ in scale size. A map that planned to show few details is designed to be of small size and thus, subjected to small scale as makes smaller representation. Conversely; a map planes to show numerous details is designed to be of large size and thus subjected to large scale as makes larger representation.

 

METHODS OF SHOWING SCALE ON MAPS.

On a map, scale can be represented by one or more of the following useful methods.

  • Statement scale.
  •  Representative fraction scale (RF Scale)
  •  Linear scale


(a)Statement scale.

This shows the relationship of distance between the map and the actual ground represented by being stated in words. E.g. one centimeter on a map represents one kilometer on the ground; 1 cm represents 1 km; or 1 cm to 1km.

Statement scale is also known as verbal scale.

Properties of statement scale.

  •  The scale on the map is expressed by being stated in words.
  •  Map distance is given in smaller unit of like centimeter and inch; while, the ground distance given in larger units of meter, feet, kilometers and miles, But it has to be noted that, cm corresponds to meters and kilometers to give metric statement scale, while inch goes corresponds to feet and miles to give imperial statement scale.

·  The amount of map distance in the scale is always 1.

 

(b)Representative fraction scale.

It is a form of scale expression in which the relationship of distance is given in ratio or fraction. It is established with special emphasize of showing the relationship of distance in similar unit. E.g. 1:50,000

Or            1

50,000

Properties of RF Scale.

·  The scale is expressed in ratio fraction with numerator and denominator.

·  The numerator stands stands for map distance; while the denominator stands for ground distance.

· The numerator and denominator treated in similar smaller units.

· The amount of numerator is 1. For instance; scale should not be expressed as 2:50,000; instead it should be 1:25,000.

·   It is neutral to metric and imperial scales.

 

(c)Linear scale.

Linear scale is alternatively known as graph plain bar, divided and open scale. It is a form of scale expression in which the line on the map shows the relation ship of distance between the map and ground represented.

 

Categories of linear scales.

Linear scales are not all the same. They are extremely varied in appearance and nature of the measurement units used. Thus, linear scales are categorized in basis of the appearance and measurement units used.

 

According to the form of appearance; linear scales are categorized into two and include:

 

  • Long linear scale.

It is a linear scale system commonly used to obtain direct accurate ground measurements especially of distance from the topographical map. It is very common on large scaled maps.

 

  • Short linear scale.

It is a linear scale system which gives a general idea on the relationship of distance between the map and actual ground represented.




According to the nature of the measurement units used, linear scales categorized into three types. These include the following:-

Metric linear scale.

It is linear scale system which uses metric units to express the relationship of distance between the map and actual ground represented.

Imperial linear scale.

It is linear scale system which uses imperial units to show the relationship of distance between the map and actual ground represented.
Double linear scale.

It is linear scale system with both metric and imperial units. Commonly on top metric or imperial units. Commonly on top metric or imperial measurements may appear, and at below the measurements in imperial or metric units may appear.

 

Properties of linear scale

  • The relationship of distance between the map and ground expressed a long a line.
  • The line scale is divided into equal parts, and each part shows the ground distance in regular interval.
  • Most of the linear scales have two major portions of primary and secondary sections.
  • The primary section is larger and placed at the right hand side of the line scale . This shows larger ground distances commonly known as primaries, and given in larger units of kilometers along the metric scale, and miles along the imperial linear scale.
  • The secondary section is smaller and placed at left of the line scale. This section is divided into fractions to show smaller ground distances known as secondary’s. These given in smaller units of merits along the metric scale, and feet along the imperial linear scale.

Note:-

Along the imperial linear scale, the larger measurements of miles indicated a long the top of the line scale; while the smaller measurements indicated along the bottom of the line scale.

DRAWING OF THE LINEAR SCALE.

The drawing of a linear scale should involves the following fundamental steps.

(i) take into consideration on the relationship of distance between the map and the actual ground represented. Assume the scale is 1 cm represents 0.5 km.

(ii) Determination (consideration) of the unit length for the linear scale drawing. It is principle for the unit length amount should measure ground distance of the whole number.
E.g.
As    1cm   =   0.5 km.
X       =  1km?

1cm x 1 km  =  1cm

0.5 km               0.5

Hence; 2cm measure 1 km along line

(iii) Draw the line to have length that evenly divided by the amount of unit length. The length. The length of the line determined by the space of the map and sometimes by the recommended ground distance to be measured along the line scale.

(iv) Dived the line scale into major portions of priary and secondary sections. Allocate 0 to separate the two sections.

(v) Sub divided the primary section into equal larger segments with respects to the amount of unit length determined.

(vi) Subdivide the secondary section into 10 smaller fractions. The length of each smaller fraction is determined by taking the amount of unit length divided by the number of smaller fractions required.

2cm  =  0.2cm

10

Hence; each smaller fraction = 0.2 cm (2mm).

(vii) The segments along the primary section and the smaller fractions along the secondary section should be proved if are accurate. It is by drawing the line of the 200 – 400 from 0 or from the left of the line towards the end of primary section. Similarly, measure the same angle from last point of primary section. Divide the angle lines into similar segments to those of base line and join the points of the three lines.

To the secondary section, draw the line of 900 downwards and upwards at last parts and they should be divided into 10 smaller units.

(viii) Finish by indicating the numbers and the used RF scale or statement scale.




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:-

·  Statement scale into scale

·   RF scale into statement scale

·  Linear scale into statement scale or RF scale

 

Statement scale into RF scale:-

Examples:

(i) 1 cm to 0.5 km.

The RF scale from the given statement scale above is determined as follows:-

·     Recall 1 km = 100,000 cm

·    Then

If 1 km = 100,000

0.5 km = ?

 

0.5km x 100,000cm = 50,000

1km
Thus,the RF scale = 1:50,000

(ii) 1cm to 0.75km.
The RF scale from the given statement scale above is determined as follows.

Recall 1km = 100,000cm
Then
if  1km = 100,000
0.75km = ?

0.75km x 100,000cm   = 75,000
1
Thus,the RF scale is 1:75,000

 RF scale into statement scale

 Examples
(i)
1:25,000
The statement scale from above RF scale is determined as follows
Recall 1km =100,000cm
Then;
if 1km   =   100,000cm

?             =     25,000cm

1km x 25,000 = 25,000           = 1
100,000cm          100,000           4
Thus;the scale is stated as 1cm represent 0.25km

(ii)1:250,000
The statement scale from the above RF scale is determined as follows.

Recall 1km =100,000cm
Then;
if 1km   =   100,000cm
?            =     25,000cm

1km x 250,000cm  = 2.5km
100,000cm

Thus; the scale is stated as stated as 1 cm represents 2.5km

 

Linear scale into statement and RF scale

Linear scale can be converted into statement scale or RF scale or RF scale by considering the unit leghth used to construct it. The unit leght is realized by measuring the length of a segment with a ruler.

According to the given linear scale above; the used unit length is; 2cm measure 3km.

Then;

As 2cms = 3km

1 cm = ?

1cm x 3km = 3km = 1.5 km

2cm 2

 

Thus; the scale is state as; 1cm represents 1.5km.From the statement scale; The RF scale becomes; 1:150,000

 IMPORTANCE OF SCALE.
Scale is useful in two varied way of map reading and interpretation;and making.

In map reading and interpretation.

  • Enables the map user to understand the relationship of distance between the map and the actual ground represented.
  • It is useful in understanding the relative size of the area mapped by considering the used scale size. For instance; if the used scale size is assessed large, it implies the used scale size is assessed small, larger area represented’
  • It is very useful in making area size, distance and gradient determination of the geographical features which appear on a map and on the actual area.
  • It is useful to judge the amount of the details of an area represented by taking into consideration of the scale size used. For instance; if the used scale is assessed large, it implies, the map makes larger representation of the small area and it is possible for many details about the area to have been included on the map.

In map making.

  • Determines the size of the map to be constructed
  • Controls the amount of details to appear on the map relatively to the size used
  • It is very useful in the cartographic process of map reduction and enlargement
  • Controls the size of the convention symbols, sign and abbreviations
  • It is useful in making map projection
  • Controls or determines the size of the ground to be mapped




EXERCISE
Q. A racing motorist travels at a speed of 120km/hr covered a ground distance measured on the map by 6cms. If traveled for 15 minutes. Determine the RF and statement scales (NECTA 1984).

Q. A racing cyclist covers a distance of 45 km between town A and b in 30 minutes. If the distance measures 3 cm on the map.

(i) Calculate the speed of the cyclist

(ii) For how long will cover 120km

(iii) Draw a linear scale to read 120 km (NECTA 2002)

 

Q (a) (i) Define a scale of a map

(ii) How important is a scale of a map to map user?

(b) (i) Given 1:50,000 state the scale into centimeters to a kilometers

(ii) Given – 1cm on a map represents 4 kilometers on the ground. Express this scale as representative fraction (RF Scale) (NECTA 1996)

 

Q. (i) Why are scale necessary in map making?

(ii) Construct a metric linear scale for 1:30,000 to measure 1.6 km (NECTA 1983)

Q. By comparing a 1;25,000 and 1;50,000 map scales, show the usefulness of scales in map reading and interpretation (NECTA 1995)

Q. (i) convert the scale of the map to a unit lenghth of one kilometer of the linear scale.

(ii) Construct the linear scale by using the RF Scale of 1:30,000 and indicate a distance of 3.6 km (EZEB 2006)

Q. A bus driver traveling along Arusha – Babati road covering a distance of 10 cms on a map in 30 minutes, if the speed of the bus was 50km/hr.

(i) Calculate the distance covered in km

(ii) Find its statements scale

(iii) Draw a liner scale using the above statement scale (NECTA 2000)

Q. Mention two uses of the representative fraction scale (NECTA 1988)

Q (a) Differentiate between large and small map scales

(b) outline the determinant factors for map scale size

(MOCK Q.)

Q. (a) Explain why scales are necessary in map making

(b) By using the unit length of 1 cm to measure 3 km; construct a linear scale to read a distance of 8.2 kilometers.

(MOCK Qn.)

Q. (a) Differentiate between small and large scale maps.

(b) Show the potential significance of scales in cartographic process. (MOCK Q.)


GEOGRAPHY FORM 5 TOPOGRAPHICAL MAP INTERPRETATION-INTRODUCTION TO A MAP
4/ 5
Oleh

No comments: