Study and Interpretation of Topographical Maps

•    Topographical maps are the maps with detailed and accurate graphical representation of natural and cultural features on the ground. Various features like mountains, hills, plateaus and plains are found on the earth’s surface.
•    Grid reference is a set of horizontal and vertical lines, like latitude and longitude to find the location of a place on a map.
•    Most of them are drawn at the interval of 1000 metres or 1 km. The origin of the gridlines is from the south-west corner of the map.
•    Topographical maps of India are prepared by the Survey of India. They map the Indian subcontinent, along with the adjacent countries. To identify an area, numbering system has been adopted. India and adjacent countries are bound between 40 parallels of latitude.
•    The whole area is divided into rectangles of 4 degree x 4 degree dimension and these are known as 4 degree sheets.
•    India with current boundary has thirty-six 4 degree sheets.
•    Each 40 sheet is subdivided into 16 equal rectangles of 10x 10 dimension. Each sheet is drawn on 1: 1:250,000 Scale.
•    Degree sheet can be further divided into four parts of 30' x 30' dimensions.
•    The four parts are referred to as cardinal directions. The four parts sheet is drawn on 1: 1,00,000 scale.
•    Degree sheet can also be divided into 16 parts of 15' x 15’ dimensions. 16 parts is known as numbering.
•    16 parts sheet is drawn on 1:50,000 scale.
•    Quarter sheet is further divided into 4 parts of 7 1/2' x 7 1/2' dimensions. It is designated by cardinal directions.
•    The methods used to show relief features on the maps are hachures, hill shading, layer tints, bench marks, spot heights and contours.
•    Contours are the imaginary lines joining places having the same elevation above the mean sea level.
•    Topographical maps show varying degrees of slopes. Closely spaced contours represent a steep slope. Widely spaced contours represent a gentle slope.
•    The slopes can be classified into gentle slope, steep slope, concave slope, convex slope and irregular slope.
•    Different types of landforms are presented differently on a topographical map depending on their slopes, like conical hill, plateau, V-shaped valley, U-shaped valley, gorge, waterfall, etc.
•    Settlements, buildings, roads and railways are important cultural features shown on topographical sheets through conventional signs, symbols and colours.
•    Map interpretation involves the study of factors that explain the causal relationship among several features shown the map.
•    A topographical sheet is usually interpreted under the following heads-marginal information, relief and drainage, land use, means of transport and communication and, human settlement.
•    Thus, with the help of the topographical maps, various natural and cultural features can be interpreted along with their relationship with each other.


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  • Q1

    What is the scale of 63K/12 map?


    The scale of 63K/12 map is 1’:1 mile or 1:50,000.

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  • Q2

    What is the longitudinal and latitudinal extent of one-inch map?


    The latitudinal and the longitudinal extent of one inch map are 15’.

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  • Q3

    Where is headquarters of Survey of India located?


    The headquarters of Survey of India is located in Dehradun.

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  • Q4

    When was the Survey of India established?


    The Survey of India was established in 1767 AD.

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  • Q5

    What is the importance of topographical maps?


    Topographical maps are important because they give detailed information of the concerned area.

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