MEASURING DISTANCES AND DIRECTIONS
Name the five basic elements of map.
The
five basic elements of map are –title, north line, direction, scale, distance.
What is the Survey of India?
The
Survey of India is the
·
The oldest scientific
department of the Government of India
·
The National Survey and Mapping
Organization is entrusted with the responsibility of exploring and mapping the
entire country.
What are the functions of the Department of Survey of
India?
The
functions of the department of Survey of India are:
1.
To provide topographic map
coverage of the entire country
2.
To demarcate and depict
the external boundaries, interstate boundaries and coastline of India on maps
What does the map title indicate?
The
title of the map indicates the topic i.e. what the map depicts or shows.
What is the north line? Where is it drawn on the map?
The North line is a
line on the map or plan indicating direction. It helps to find directions with
respect to north.
The North Line drawn on the top of the map.
In the absence of the north line on the map how does
one find the north direction?
In the absence of
the North line
·
The top portion of the map
is considered north
·
The bottom portion is
considered south
·
The right portion is
considered east
·
The left portion is
considered West
What are cardinal directions?
The
cardinal directions are the four main directions namely North, East, South and
West.
What are intermediate directions?
The
intermediate directions are the divisions of cardinal directions.
They are North East, South East, South West and North West.
Why are the cardinal directions divided and subdivided?
The
four Cardinal directions are divided into eight intermediate directions. These
intermediate directions are further subdivided into sixteen directions for
greater accuracy.
What are the divisions cardinal directions called?
The
divisions of cardinal directions are called intermediate directions.
They are
North East, South East, South West and North West
What degrees correspond with the North, East, South, West
directions?
The
degrees which correspond with North, East, South, and West are:
North
-0º
East-
90 º
South-180
º
West-
270 º
Name the two instruments used to measure directions?
The
two instruments used to measure directions are:
1.
The Mariner’s Compass
2.
The Prismatic Compass
What is a scale?
A
scale is a ratio between the distance on the map and the actual distance on the
Earth’s surface.
What are the uses of scale? Name the three types of
scale.
Scales
are used to reduce or enlarge the areas on the earth’s surface.
The
three types of scales are
1.
Verbal Scale
2.
Graphical or Linear Scale
3.
Representative Fraction
Explain the verbal scale?
The
verbal scale is stated in words.
The
units are mentioned in this type of scale i.e. 1cm=5km or 1cm to 5km.
It
means that 1cm on the map is equal to 5km on the ground.
What is a graphical or linear scale? Where is it
usually drawn?
A
Graphical scale consists of a straight line which is divided into lengths that
represent given distances on the Earth’s surface.
It
is usually drawn near the lower portion of the map.
Explain the following diagram.
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This is a diagram of a linear or graphic scale.
The linear scale line is divided into 5 equal parts, 1 cm apart.
Each of these parts represents a distance of 50 km on the ground.
At the extreme end one part of 1 cm has been subdivided into two parts to of 5mm each representing 25 km.
What is representative fraction? Explain.
·
The Representative
Fraction is one which has the numerator expressing the distance on the map and
the denominator expressing the distance on the ground.
·
The numerator is always 1.
·
Both the numerator and
denominator are expressed in the same unit.
R.F. =Distance on
the map/ Distance on the ground
or
1/50,000 Or 1:50,000
·
This means that 1cm on the
map represents 50,000 cm on the ground on the map the R.F. will be written as
1:50,000 or 1/50,000
How are distances measured on a map along a straight
line?
Distances
between two points on the map along a straight line are measured using a ruler.
The actual distance is calculated by converting the measured distance into
actual distance on the ground by using the scale of the map.
What are the two methods of measuring distances along a
curved line?
The
two methods to calculate distances along a curved line are the twine method and
the divider method.
Explain the twine method.
·
In the twine method, a
twine is placed along a feature to be measured carefully following the curves
and bends.
·
The length of the twine is
then measured in centimeters and inches using a ruler or a linear scale.
·
The actual distance on the
ground is calculated by converting the length of the twine by using the scale
of the map.
Explain the divider method
·
In the divider method, a
divider is used whose points are fixed at 1cm or 2cm apart
·
Beginning at one end, the
divider is turned continuously till the other end is reached.
·
The number of turns is
counted.
·
The actual distance on the
ground is calculated by converting the number of counts by using the scale of
the map.
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