Concept of Map, Importance and Use

 Map is a very important tool for a geographer. A clear idea can be formed about a region from it. We can show the whole world or a part of it through a map. We can provide information about a particular region by drawing a map and using some signs. A map is necessary not only for the geographer but also for all people especially travelers, administrators, planners, architects, engineers, agriculturists, meteorologists and even the common people. In this article classification of map, its importance, uses, local time and standard time etc. will be discussed.

At the end of this article, we will be able to :

• Explain the concept, importance and use, of a map.

• Describe the maps of various kinds.

• Explain how to present information on a map for practical use.

• Explain local time and standard time.

• Explain why time changes from place to place?

• Use of GPS and GIS in the map.

Look at the following map. It is the administrative map of Bangladesh. On the paper the international boundary of Bangladesh, countries around the borders of Bangladesh are located and the sea is drawn. Besides these, it also shows the seven divisions, the districts in each division, their names and areas. The whole administrative area has been shown in one page (fig. 3.1). In this way, the whole world, different continents, countries or different divisions and districts can be shown on a map in one page.

You might have seen a wall map in your school. In your Geography and Environment books or in any atlas you might have seen maps. Map gives us ideas about a region, the nature of land, climate, plants, earth, water and many other things. We can learn a lot about different continents and oceans through it. The map may be defined as a representation of the earth's pattern as a whole or a part of it on a plane surface with conventional signs, drawn to a scale and projection so that each and every point on it correspond to the actual part.

The word map comes from the Latin words 'mappa'. In earlier times maps were drawn on clothes. The size of the map varies according to scale. There are three ways with which the scale of the map is shown.

Methods of showing scale

(a) By statement

(b) By graphical scale

(c) By representative fraction or R.F.

(a) By statement : We express the scale by statement such as four miles to one inch, one mile to 16 inches, etc. in every respect the first 1 (inch) is the map distance and second number (mile, yard, kilometre) is the distance on the ground.

(b) By graphical scale : The scale of map can be expressed by dividing a particular line into a number of equal parts and is marked to show what these divisions represent on the actual ground. By drawing a line of 5 centimetres and dividing it into 5 equal parts, each part is 10 kilometres (fig. 3.2). Leaving one centimetres on the left side and further dividing into equal parts of smaller sections each representing 2 kilometres.

(c) By representative fraction or R.F: Representative fraction expresses the proportion of the scale by a fraction in which the numerator is one and the denominators also in the same unit. Representation fraction is commonly written as R.F. and is shown in the map as 1: 100,000. This means one unit on the map represents 100,000 on the ground. If the 1 unit is in inch then 100,000 is also in inch, if it is in centimetres then both the units should be same. The formula of calculating R.F. is given below:

R.F = (Map distance)/(Ground distance)

Information that will be given in a map depends on (a) scale, (b) projection, (c) conventional signs, (d) skill of the cartographer and the, (e) type of map.

In the modern world, use of maps is very important. Map is known as the tools of geography but it is also very important for the students, historians, engineers, businessmen, journalist, soldiers, pilots, captains of the ships and many more.

Classification of Maps

There may be various types of maps. Generally, on the basis of scale used in scale, again the maps and subject matter, the maps are classified into two groups. According to the maps are of two types: (a) large scale maps and (b) small scale maps.

Navigation charts, aeronautical charts, mouza maps or cadastral maps are large scale maps. As a small area is enlarged, so many date or information can be accommodated in the map. Atlases, wall maps are small scale maps. The whole world or the continent or any big region like that of a country when shown on a sheet of paper, small space remains in the map. So, shown on this type of map.

There are many types of maps:

1. Cadastral or Mouza map: The term cadastral is derived from French word 'cadestre' meaning register of territorial property. The cadastral maps are drawn to register the ownership of landed property by demarcating the boundaries of fields and buildings. The village maps of our country and the city plan maps belong to this category (fig. 3.3). These maps are very large scale maps which are drawn on a scale of 16 inch to 1 mile or 32 inch to 1 mile.

2. Topographic map : Topographic maps are made on a large scale on the basis of precise survey of the area. They show general surface features in detail which contain both natural landscape and man-made features. The scale of the topographic map varies from 1 inch to 1 mile to ¼ inch to 1 mile. Topographic map shows relief, rivers, forests, villages, towns, roads and railways (fig. 3.4). The topographic maps are prepared in different scales in different countries. The standard and most popular topographic survey map of British Ordinance Survey is 1 inch to 1 mile. Topographic maps of Bangladesh have been made into three scales. i.e. (i.) 1 inch= 1 mile, (ii.) 1 :50,000 and (iii.) 1 :250,000. The last two types of scales have been adopted for the latest topographic maps of Bangladesh.

3. Wall map : Wall maps are generally drawn for using in the classroom. The world as a whole or in hemispheres are shown on the wall maps. Wall maps may also be prepared for a country or continent, large or small according to need (fig. 3.5). Their scale is smaller than topographic maps but larger than atlas map.

4. Chorographical or Atlas map : A collection of map is called an Atlas. The scale of the atlas map varies from 1: 100,000 to 1: 1000,000. These are small scale map which gives a more or less highly generalized information regarding the physical and economic conditions of different regions of the world

5. Physical map : Map which shows the natural features as mountains, plains, rivers, deserts, wetlands of a country or a region is known as physical maps. These natural features are shown with different colours. Plants are shown by green colour, mountains and hills by brown colour, rivers and water bodies by blue colour and highland or plateau by yellow or orange colour.

6. Geological map : The rocks that form the crust of the earth, their mode of formation and deposition are shown on geological map.

7. Climatic map : The climatic map shows the average condition of temperature, pressure, wind and precipitation of a region over a long period of time.

8. Vegetation map : Vegetation map shows the natural vegetation of a region.

9. Soil map : The soil map shows the various types of soil covering the area. Agriculturists use this map usually as it highlights the quality of soil of a particular area.

10. Cultural map : Economic condition, political boundary, historical places are shown on cultural maps. Cultural map can be divided into some parts. These are :

a. Political map : Most widely used map showing the boundary of a region, country, division, districts etc.

b. Distribution map : Map showing the distribution of population, crops, animals, industries of a region or a country is known as the distribution map.

c. Historical map :Map showing places of historical importance is the historical map.

d. Social map : Map showing the distribution of religion, language, nationality is known as social map.

e. Land use map : Major land uses of an area or region are shown in land use maps. These maps show various kinds of land uses in urban and rural areas such as roads, buildings, industries and parks are shown in urban land use maps and cropland, homestead, fallow land, forest etc. are shown on a rural land use map.

Techniques of Presenting Information in a Map

A Map is a geographer's tool which is used by various types of people from different occupations. The natural and cultural features that are shown in a map should be universal, so that people belonging to any country can read the map by knowing the international conventional signs used in the map. The international conventional signs are given so that students have a general understanding of those signs (fig. 3.6).

Marginal information of a map : All the information required to understand a map should be around its margins. Marginal information includes (i) Title/heading, (ii) Scale, (iii) North line, (iv) Legend and (v) Source of data.

(i) Title/heading : Each map has a title or heading. It shows the type of map. If it is a political map of Bangladesh, the title will be 'political map' followed by Bangladesh.

(ii) Scale : There are three common ways to show the scale by statement, representative fraction/RF or linear or graphical scale.

(iii) North line : North line is important for a map. It is usually considered the top section of the map as northern part of the map. North line can be shown anywhere in the map within the margin of the map. The position of the north line depends on the layout and size of the map within the margin.

(iv) Legend : In each map some data is presented in the form of some conventional signs, colour or shades. The representing signs, colours and shades are shown in the legend.

(v) Source of data : All maps are drawn on the basis of information or data so the source of data should be provided outside the margin i.e. border of the map layout.

Local Time and Standard Time

As the earth rotates, every place has its sunrise, sunset and noon. When the Sun is at its highest point in the sky, it is noon and also known as zenith. The earth rotates from west to east. So, places in the east see the Sun first. Places in the west see it later. So, for each 1 ° of longitude towards the east, a time of 4 minutes has to be added. For each 1 ° of longitude towards the west a time of 4 minutes to be subtracted from the Greenwich Mean Time or GMT, which is the 0° meridian or prime meridian located at Greenwich in London.

Local time

Everyday the earth moves round her axis from west to east. As a result, the sun appears earlier in the places located in the east. Due to rotation of the earth, the sun reaches the zenith of the sky, or in other words, the sun reaches its highest altitude on a certain place and that hour is treated as 12:00 noon. On the basis of this noon time, the other time for the day is determined. The time thus determined is the local time for that place. So, the local time of a place is determined on the basis of the highest altitude of the sun which can be observed with the help of a sextant.

The earth at the centre creates 360°. The earth requires 1,440 minutes (24 hours x 60 minutes) to cover this distance of 360° for one time. So, the earth needs 4 minutes (1,440 + 360) to rotate 1 ° of longitude. Therefore, for 1° difference of longitude, the difference of time will be 4 minutes.

Standard Time

In any country there are many meridians of longitude that run through the country. If there are ten meridians running through a country as each meridian is 4 minutes apart so, 10 x 4 = 40 minutes, so in that country there will be ten different local times according to the meridians. To avoid this confusion, the local time of a central meridian of a country is taken as the time for the whole country. This is called the Standard time. Some countries have great longitudinal extent, so they have more than one standard time. Example USA has five and Canada six time zones.

There is a general understanding among the countries of the world to select the standard meridian of any country in multiples of 7.5° longitude. Every 7.5° longitude makes a difference of 30 minutes.

Time Difference on the Basis of Location

In the earlier chapter we have seen for 1 ° longitude, the time difference is 4 minutes. We know, earth rotates from West to East. For this reason, in Bangladesh day comes earlier in the places which are located in the East than those which are located in the West. From this we can understand that morning comes earlier in those countries which are located in the East of Bangladesh and those countries which are located in the West of Bangladesh, morning comes later.

We know for the difference of 1 ° longitude, time difference becomes 4 minutes. This 1 ° is divided into 60 minutes and for every 1 minute, time difference becomes 4 seconds. So, for 60 minutes it requires 60 x 4 = 240 seconds or 4 minutes.

GPS and GIS Maps

At present the use of GPS and GIS are the most modem form of information for study and management. The English of GPS is Global Positioning System. If we want to know the global location of a certain place, the easiest way of knowing it is through GPS. Through GPS the latitude, longitude, height and distance of a certain place can be found. Besides, the north line, date and time of that place can be known.

Working Principle ofGPS

GPS collects information from the land-satellite through its receiver. To collect this information GPS needs cloud free sky. The GPS machine can work accurately in the clear sky. Sometimes it faces problems to identify the location of steep high hills, buildings and it is time consuming also.

Benefits of GPS : Among many discoveries of technology GPS has earned a wide popularity as a very valuable tool for the geographers. With the help of this tool we can find out latitude, longitude and other matters within seconds. In our country a great problem lies in land surveying. We will be able to identify the boundary of our land without any problem. This will save much of our time. During any natural disaster we will be able to send relief goods to a certain place by identifying its exact location by latitude and longitude with this GPS.

Demerits of GPS: GPS has some problems along with its benefits. These are-its price is high, so it is not easily available. Most of the people are not familiar with it. Besides these, people tend to use traditional system.

Geographical Information System

Storing and analyzing geographical information system is known as GIS. It is a computerized system of storing information and analysis. This system helps to prepare future plan through storing geographical information, analysis and management, identifying spatial problem. The use of GIS started first in 1964 in Canada. Gradually people started using it widely around 1980. At present it is being used in land management, natural resource development, water research, urban and regional planning, population analysis, transport and communication system analysis.

The utility of a map is increased by it through the presentation of many kinds of data and analyzing those data in the map. For example, we can have a full idea of a particular place by showing its water management, topography, land use, communication, soil, road etc. in a map.