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Various types of symbols are used in different types of maps: 1. Atlases 2. Relief Maps 3. Weather Maps.
1. Symbols Used in Atlases:
No one can understand the importance of Atlas as a students can. Atlas is a book of maps which is a combination of maps of continents, Oceans, Countries and specially the natural political regions of India.
Natural Maps:
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Colours play an important role in these maps. Each colour represents particular height and depth. To understand these features, index is provided with each map. For heights we use greens, yellow, orange, brown, red and white colours. On the other hand blue colour is used for depth. It varies from light blue to dark blue, as the depth increases the darkness of blue colour also increases.
In political maps colours are used to differentiate any region from another. For example, various states (provinces) of a country are represented by different colours in the map of a country. On the other hand different nations are represented by different colours and in a World map single or same colour is used for all the states of a country. Similarly in the map of state different colours are used for different districts.
We should take care of certain aspects while selecting the colours for maps because the effectiveness of map decreases if we use the colour of same tone in a map, showing places near to each other. Similarly, if the number of regions is large then we can repeat same colour but it should not be used physically near to previous one. Use of colours in political map is an art which depends on an aesthetic sense of map maker.
The line separating one region from another is known as boundary or border. These are classified on the basis of their importance. Border between two countries, two states, two districts and two tehsils (sub-divisions) can be shown in a map. All these boundaries have their own importance therefore different symbols are used for their representation.
Use of different ‘stensils’ is also related with importance of a place, E.g- In map of India, different stensils are used for writing the name of our country, Neighbouring countries, Names of States, Names of Capitals and Cities. So that the map user can easily understand the difference between all these.
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2. Use of Symbols in Relief Maps:
Commonly used large scale relief maps are very important for ‘geographers’ and ‘armies’ as well because all other maps are prepared on the basis of these maps. These maps provide information about Relief, Vegetation, Water bodies, Population, Agriculture and Transportation Because of such features these are very popular and important. Use of traditional and cultural symbols is highest common in these maps that is why two lines on indexes are found on such maps.
There are hundreds of traditional and cultural symbols which may be learnt on the basis of use and experience. For the facility of students teachers can share the information about the symbols from a regional map of Punjab and the regions represented by these symbols.
Commonly used symbols have been shown on a map. It is really important to understand the role of colours in these symbols.
3. Use of Symbols in Weather Maps:
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Conditions of a place during a particular time related with temperature, atmosphere, winds, humidity, clouds and rain are known as weather of that place. Representation of all these conditions on a map is known as weather map. Indian weather department is stationed in New Delhi.
This department collects information from various weather stations located in India. On the basis of this information this department makes maps twice a day and publishes them. This information is very helpful for armies, pilots, fishermen, navigators, farmers and other people also. Various symbols are used to represent the aspects of weather.
i. Temperature:
Temperature is shown on map with the help of isotherms which are imaginary lines drawn on a map connecting the regions having similar temperature. For marking these isotherms, mean average temperature is set at sea level which minimises the variation on the basis of increase in height.
One of the two smaller maps given below the main map gives information about the difference between the highest temperature and normal temperature and other map gives information about the difference between the normal and lowest temperature. Average temperature of last 30-35 years of a particular place is known as normal temperature.
ii. Air Pressure:
Like temperature imaginary lines are also used to represent the Air pressure known as isobars. Isobars are used to represent to air pressure of particular place on a map. Air pressure is measured in ‘millibars’. A value is written with air pressure lines. This value represents the air pressure of a place from where to pass. e.g. 1012 mb,1014 mb
Air pressure lines are drawn with the difference of two millibars. Their shape depends on the air pressure of a particular place, they might be circular or ‘U’ shaped. Difference between two air pressure lines represents the pressure variation at a place.
iii. Clouds:
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To collect information about the situation of cloudy sky is divided into four imaginary parts and clouds are divided into eight. On the basis of this side ‘O’ represents clear sky and ‘8’ represents ‘over cast’.
With the same process intermediate conditions are measured. Sky is represented by circles on a map and these are darkened according to the presence of clouds.
iv. Winds:
Winds always blow from high pressure to low pressure regions. On a map winds are represented by lines, which are connected with the circles showing the condition of clouds. Speed and direction of winds are two important aspects. Windvane or windcock is used to find the direction of winds.
This instrument is actually a liver which moves freely on a pivot having signs showing four or eight directions around it. Importance of this moving instrument lies in its shape as its narrower side faces toward the direction, wind is blowing from and broader side turns to the direction, wind is blowing to.
Anemometer is used to measure the speed of wind. It consists of four hemispherical cups, each mounted at equal angles to each other on a vertical shaft. It moves with the blowing effect of wind while an instrument fitted beneath it turns its rotational speed into speed of wind which is measured on kilometer per hour scale.
Speed of wind is shown in weather maps with the help of big and small lines marked in the direction of wind itself.
Knot stands for Nautical mile per hour. 1 Nautical mile- 1852 meters on land. An oceanic mile is slightly bigger than the mile on land.
v. Other Weather Aspects:
a. Hail:
Precipitation in the form of spherical or irregular pellets of ice larger than 2 mm and their weight may vary upto 2 pounds.
b. Snowfall:
Snowfall is the precipitation in the form of flakes of crystalline water ice that falls from clouds. These are very soft.
c. Rain:
It is the major form of precipitation in which water droplets fall.
d. Drizzle:
In this the size of water droplets is smaller than 2mm,
e. Snow Rain:
It is the combination of snowfall and Rain.
f. Fog:
Fog is collection of water droplets suspended in the air near the Earth’s surface. It decreases the visibility forms of fog on the basis of visibility
Fog = Ground frost — Light Ground frost
g. Frost:
When condensation takes place at the temperature lower than 0°c, water vapours turn into snow particles.
h. Dew:
Dew is water in form of droplets that freezes on trees, plants and other exposed objects due to condensation of vapours present in air. This process takes place due to fall in temperature during night.
i. Storm:
As wind blows, it takes dust particles with it, known as storm.
j. Lightening & Thunder:
vi. Sea Conditions:
In weather maps of India situation of waves of Arabian Sea, Bay of Bengal and Indian Ocean are shown. Initials of English have been used to show the condition of waves according to the scale of calm to high and dangerous waves.
