Topic
1-Geoid : the spherical shape of the earth, slightly flattened at the poles.
2-Globe : A three-dimensional spherical model of the earth and its surface.
3- Map : A representation of the earth's surface and a part of it on a flat surface according to scale.
4- Cartography : The science of map making
5- Conventional symbols : Symbols used by general agreement to make map clear and easy to read.
6- Thematic Map : A map which depicts a certain theme and subject, such as rainfall map, population map.
7- Aerial Photography : A photograph of an area taken form the air.
8- Plan : A detailed drawing of a small area on scale.
9- Sketche : A rough drawing of an area drawn quickly without a scale.
GLOBE
For long, people believed teh earth to be flat. But,later, scientists proved that the earth is spherical, slightly flattened at the poles. This particular shape of the earth is called 'geoid'. Photographs taken from the space have confirmed the spherical shape of the earth. Since photographs are two dimensional only, they cannot provide the realist view of the earth. The shape of the earth can better be represented by a globe which is a true replica or model of the earth. It correctly shows the poles, latitude, longitude,oceans and continents,etc., because it gives the three-dimensional view of the earth.
Merits of the Globe
Though the globe gives us the correct picture of the earth, yet 'it has certain disadvantages or limitations. It is not easy to carry the globe everywhere, although nowadays folded globes are also available which are more handy than the earlier ones. Moreover,the globe cannot provide us specific information about a small place,area, district or a state. In spite of all the limitations,globe has many advantages. It can be rotated,just as the earth rotates on its axis. We can easily understand the changes of seasons on the earth. Distances, directions and exact shapes of continents and oceans,etc.,are best represented on the globe.
MAPS
A map is a two-dimensional picture of the earth's surface or a part of it on a flat surface according to scale.
Maps have been in use since the early civilizations. The Babylonians were, perhaps, the first to prepare a map on a clay tablet, as early as 2300BC . Ancient people employed different techniques to prepare maps. The Eskimos of Greenland used to cut coastal islands in a dark coloured animals skin. Ancient Egyptians used to engrave maps on metal plates. The. inhabitants of the Pacific Islands used to make plans by knotting reeds. However,all these maps lacked authenticity.
The first ever map of the world was prepared by the Greek scholar Anaximander (611=541 BC ).
However,map making on a scientific line began with the world map drawn by Claudius Ptolemy, an Egyptian geography,who lived in the second century BC. Gradually, Cartography, the science of map making, developed on scientific lines.
**Essentials of Map **
Distance, direction,and symbols are teh three essential of map making. These features of a map are know as 'the language of map ', because with the help of these features we can easily study and interpret a map.
1.Distance : We know that the distances on the earth are very great. We cannot depict the actual distances on a map,drawn on a limited sheet of pepar. To overcome this difficulty,we need to proportionally reduce distances of the ground while depicting them on a paper. This can easily be done with the help of a scale.
Scale is an important device to depict the reduced distances on the paper. It is a ratio and proportion between the actual distance between two points on the ground and the same distance shown on the map.
There are two principal methods of showing the scale on a map:
1 Statement method : In this method, the distance between two points on the ground and the same distance on map is shown by a statement. For example, if the distance between your home and your school is 10 kilometres,you can show this distance on the map by 1 centimetre. The scale of the map will be : 1 centimetre- 10 kilometres.
**2 Graphical method **when the scale is shown on a map by a line divided into smaller parts, it is called graphical scale or liner scale.
On basic of the scale, a map may be a large scale map or a small scale map. When a map shows larger areas such as continents or countries,on a small scale, we call it a small scale map. On the other hand, when we show smaller areas such as a city , a town or a village,on a large scale, it is called a large scale map.
2 Direction : Direction is also an essential features of a map. There are four principal direction=North, South,Eat,West. These are called cardinal points. Onces the main direction is known,others can easily be identified. In a map,only the north direction is shown with an arrow near the top , towards the right. The top of the arrow is marked with the letter 'N' which denotes north. This is called the North Line. An instrument called compass is used to find the main direction. Compass was invented by the Chinese.
3 Symbols : On a map, it is not possible to show various features as existing on the ground. In a given area,there may be several physical features,such as hills and rivers, or cultural features like buildings,roads,railways lines, parks, etc. Therefore, specific signs or symbols are used to represent these features on a map. The use of symbols saves space. Such symbols are known as conventional symbols. There is a general agreement l over the world regarding the use of such symbols. These symbols are commonly used in topographic maps.
With the help of symbols,basic information about a place or an area is easily obtained,even if one does not understand the local language. Such maps facilitate you to have prior information of an unknown area that would like to visit. Tourists especially benefit from such maps.
Types of Maps
Maps can be classified on several bases. As mentioned earlier,on the basis of scale there may be small scale and large scale maps. On the basis of specific information,there may be physical map,soil map, vegetation map, political map, population map, road map and so on. Such maps represent certain topic or theme,hence,called Thematic Maps. Maps are also used to explain historical events such as an. important voyage, a war, speard of civilization, or the extent of a kingdom. Such maps are called Historical maps.
There has been great advancement in the technique of map making. Nowadays maps are made using a computer. Such maps are very sharp, attractive and accurate. A comparison between an ancient map and a modern map clearly shows an improvement in the quality of maps being produced nowadays.
This has been possible due to improved technology only:
Aerial Photograph and Satellite Image
In the later part of the twentieth century major scientific advances have been made in map making. The surface of the land and oceans is photographed by cameras mounted on aircraft. The aircrafts fly between heights of 500 and 6,000 meters above the ground and take pictures of the earth. These pictures are called aerial photographs. From these photographs, excellent maps are made.
Satellites, mounted with cameras also take pictures of the earth from a greater distance in space. These pictures called satellite images. They are also used widely in the country.
PLAN
A plan is an outline drawing of a building area, or a room. It depicts all the details minutely. A palm,like a map ,is drawn true to scale and direction but, it differs from a map significantly. A map shows only important features of an area, while a plan shows the detailed layout of buildings and spaces. In case of the plan of a classroom, the arrangement of desks and benches, teacher's table, black-board, cup-boards, windows, doors, etc.has to be shown. The scale of such plans is usually large, e.g. 1 centimetre- 1 metre. Unlike sketches plans are very accurate. It also shows the correct distances between places.
SKETCH
A sketch is a rough drawing without a scale showing a small area in greater details. A sketch does not have a scale,title index or direction. It simply shows the relative location of a few selected features,not drawn to scale. Sketches prove very handy in locating places. You can help your friend by drawing a sketch of your locality and its roads,if he wants to come to your house. You may tell him important landmarks of the route to your house.