Map and Globe
2.1 SHAPE OF THE EARTH
Today all of us are aware that the shape
of the earth is spherical. Do you know that it was thought to be flat like a
disk or square in ancient times? People feared venturing out far into the sea
lest they might fall off the edge of the earth. This idea about the earth's
shape was accepted until Aristotle made the following observations to prove
that the shape of the earth was spherical.
The earth's shadow during lunar eclipse
is curved and
The ships disappear hull first when they
sail over the horizon.
Today it is scientifically established
that the earth is an oblate spheroid. It is slightly flattened at the poles and
bulging at the equator due to its rotation, We now know that the planet's
equatorial diameter is larger than its polar diameter, contributing to its
shape.
2.2 GLOBE
A globe is a three-dimensional model of
the Earth. It is usually mounted on a stand at an angle to represent the
Earth's tilted axis. It is also not fixed. It can be spun from west to east,
just like the Earth rotates on its axis. That is why a globe is called a true
model of the Earth. It not only represents the exact shape of the Earth, but
also the relative sizes, shapes, distances, and directions of all the
continents and oceans.
Globes are of two types - political
globes which represent political divisions of the Earth and physical globes
which represent physical features of the Earth. A major drawback of using
globes is that they do not allow us to see the entire Earth at a single glance.
Another drawback is that the physical features of the Earth or a particular
region cannot be studied in detail. Globes are also difficult to carry.
MAP 2.3
A map is a two-dimensional
representation of the entire or a part of the Earth's surface drawn according
to a scale on a flat surface. Maps are drawn from aerial photographs of the
Earth. But unlike aerial photographs, maps only show some information. Maps are
more useful than globes because they allow us to study specific parts of the
Earth, such as continents, countries, states, cities, or villages. They give
more detailed information than globes and are easier to carry around.
Maps can be physical, political, or
thematic. Physical or relief maps show physical features like mountains,
plains, plateaus, water bodies, etc. Political maps show different countries
and states, cities, towns, and villages along with their political boundaries.
Thematic maps are based on specific themes. They provide specific information like road or
railway networks, soil, distribution of forests, industries, rainfall, etc.
They are named according to the information they provide, for example, rainfall
maps, road maps, mineral distribution maps, etc.
A collection of maps in a book form is
called an atlas. Earlier, maps were drawn by hand on clay tablets, metal
plates, animal skins, cloth pieces, etc. Nowadays, they are drawn with
computer-aided machines, which are very accurate and precise.
The main drawback of maps is that they
do not represent accurate shapes and sizes of continents and oceans. For
example, on the world map, the Polar regions of the Earth get stretched much
beyond their actual size.
To understand this better, take a rubber
ball and trace some patterns on it. Cut the rubber ball in half and place the
halves side by side. Try and flatten them out. You will find that the drawings
will seem distorted.
|
Cartography The
science of making maps is called cartography. The first maps were made on
paper by hand and therefore varied in quality. They were also limited in
distribution. Nowadays we have digital maps, i.e., maps made in digital
format which can be accessed through a computer. Besides software for making
maps, cartographers can now take help of satellite images of the Earth to
produce accurate and updated maps of the Earth. |
2.4 HOW TO READ MAPS
Maps are by far the most important tools
for studying the Earth. But one must know how to read them in order to use them
effectively. The language of maps comprises the following elements which help
us to read them:
TITLE
The title of a map tells us what it is
about. It tells us whether the map is a physical map of India, a road map of
Chandigarh, a map about annual rainfall in
SCALE
Maps represent large areas of the Earth
on a small space. They reduce the entire world or a portion of it to fit into a
paper in such a way that they represent the correct distance between places. A
particular distance on a map represents a particular distance on the ground.
This relation is called the scale of the map.
The scale is always given on a map.
There are different ways to represent the scale:-
1. By a Statement: The scale is described in words. For example, a map may state '10 cm on the map represents 500 m'. This means 10 cm on the map = 500 m on the ground.
By Representative Fraction (RF): The
scale is given as a fraction For example, 1cm:10,00,000 km or 1cm/10,00,000 km.
This means that 1 cm on map represents 10,00,000 km on ground.
By Linear Scale: The scale is shown as a
straight line with uniform divisions, These divisions are used to measure the
distance between two points on a map, length of a road, length of a river, etc.
This is done with the help of a string. To measure a length or distance, a
string is put on the required spots on the map and they are marked on the
string with a pen. The string is then put on the linear scale and the distance
or length between the two markings is measured.
Every map has its own scale. The scale
of a map depends upon the purpose for which map is being made. Depending on the
scale, maps can be categorized into two types - large scale maps and small
scale maps.
A large scale map represents a small
area in great detail. For example, a road map of a city. A large distance on
the map represents a small distance on the ground. That means, a distance of 10
cm on the map may represent only 1000 metres on the ground.
A small scale map represents a large
area with fewer details. For example, a world map. A small distance on the map
represents a very large distance on the ground. So, 10 cm on the map may
represent an actual distance of 1000 km.
DIRECTION
There are four cardinal points or main directions
namely, north (N), south (S), east (E), and west (W). Between them lie the four
intermediate directions namely, northeast (NE), northwest (NW), southeast (SE),
and southwest (SW).
On the top right corner of any map, you
will find an arrow marked 'N'. This arrow represents the north direction and is
known as the north line. This can help you find other directions. The south is
opposite to the north direction, the east is to the right, and the west is to
the left. We can find out the main directions with the help of an instrument
called compass. A compass has a magnetic needle which always points in the
north- south direction.
KEY
Maps have a key or index at the bottom
left-hand corner. This tells us what the various symbols on the map represent.
As it is not possible to show the actual shape and size of features on the map,
they are represented through symbols. Symbols comprise letters, shades,
colours, pictures, or lines. The use of symbols makes the reading and drawing
of a map easier and quicker. Certain symbols are universally accepted, i.e.,
all maps use these symbols. Such symbols are known as conventional symbols.
Like symbols, there is international agreement regarding use of colours.
Colours are used to represent major landforms. Green is used for plains, yellow
for deserts, brown for highlands, and blue for oceans and seas.
2.5 SKETCH AND PLAN
Sketch- A sketch is a rough map drawn without a scale. It
does not give accurate information. It only conveys a rough idea of the place
Directions and distances are shown in sketches but no scale is used. Therefore,
such maps do not give us much idea about the distance between places or their
location. Sketches are often drawn to tell the routes or locations of
particular places in a given locality.
Plan -A plan is s a large scale map of a small area. It is
often drawn to show the layout of a building room, shopping complex, class
room, etc. It gives all the minor details of the area and is very accurate) It
is often used by architects who design houses and buildings.
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