NCERT Class 11 Geography | Chapter 2 — Complete Terminology
1. ⭐ Core Terminology
Scale → Relationship between distance on a map and the corresponding distance on the ground.
Map Distance → Distance measured between two points on the map.
Ground Distance → Actual corresponding distance between the same two points on the Earth's surface.
Scale Ratio → Ratio between map distance and corresponding ground distance.
Numerator → Number above the line in a fraction. In 1 : 50,000, numerator = 1.
Denominator → Number below the line in a fraction. In 1 : 50,000, denominator = 50,000.
Representative Fraction (R.F.) → Scale expressed as a fraction showing the ratio between a unit distance on the map and the same unit distance on the ground.
Sketch → A network of lines/polygons without a scale.
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2. 📌 Methods of Showing Scale
There are 3 major methods:
① Statement of Scale
Scale expressed as a written statement.
Example:
> 1 cm represents 10 km
Meaning → 1 cm on map = 10 km on ground.
Another example:
> 1 inch represents 10 miles
Advantages
Simplest method.
Easy to understand for people familiar with the measurement system.
Limitations
May not be understood by people using another measurement system.
Becomes redundant when the map is enlarged or reduced.
A new scale must be worked out.
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② Graphical Scale / Bar Scale
Scale represented by a line/bar divided into sections.
Shows map distance and corresponding ground distance.
Has primary divisions and secondary divisions.
Can be expressed in kilometres/metres or miles/furlongs.
⭐ Most important advantage:
> Graphical scale remains valid even when the map is reduced or enlarged.
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③ Representative Fraction (R.F.)
A numerical/fractional representation of scale.
Example:
> 1 : 24,000
Means:
1 unit on map = 24,000 of the same units on ground.
Therefore:
1 mm → 24,000 mm
1 cm → 24,000 cm
1 inch → 24,000 inches
⭐ R.F. is called the Universal Method because it is expressed in units without specifying a particular measurement system.
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3. 🌍 Systems of Measurement
Metric System
Used in India and many other countries.
Important conversions:
1 km = 1,000 m
1 m = 100 cm
1 cm = 10 mm
1 km = 100,000 cm
English System
Prevalent in the United States and United Kingdom.
1 mile = 8 furlongs
1 furlong = 220 yards
1 yard = 3 feet
1 foot = 12 inches
1 mile = 63,360 inches
📌 Exam fact: India used the English system for measuring/showing linear distances before 1957.
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4. 🔢 R.F. — Important Concepts
R.F. Formula
R.F. = Map Distance / Ground Distance
⚠️ Both distances must be expressed in the same units.
Example:
1 : 50,000
means:
> 1 unit map distance = 50,000 same units ground distance.
Why is R.F. written as a fraction?
Because it indicates how much the real world has been reduced to fit on a map.
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5. 🔄 Conversion Terminology
Statement of Scale → R.F.
Procedure
1. Convert ground distance into the same unit as map distance.
2. Remove the units.
3. Express as 1 : denominator.
Example
1 inch represents 4 miles
1 mile = 63,360 inches
Therefore:
4 miles = 4 × 63,360
= 253,440 inches
So:
R.F. = 1 : 253,440
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6. 🔄 R.F. → Statement of Scale
Example:
R.F. = 1 : 253,440
This means:
1 unit on map = 253,440 units on ground.
For metric conversion:
1 cm = 253,440 cm
Since:
1 km = 100,000 cm
Therefore:
253,440 ÷ 100,000 = 2.5344 km
So:
> 1 cm represents 2.53 km approximately.
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7. 📏 Graphical/Bar Scale Terminology
Graphical Scale
A scale represented by a line/bar divided into measurable units.
Bar Scale
Another name for graphical scale.
Primary Divisions
The main divisions of the scale bar.
Secondary Divisions
Smaller subdivisions used for measuring shorter distances.
Zero Mark / 0 Mark
Reference point from which the scale divisions are measured.
Round Number
A convenient whole number selected for constructing a graphical scale.
Example:
If calculation gives 7.5 km, a convenient round number may be 5 km or 10 km.
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8. ⭐ Important Construction Facts
Metric Graphical Scale
By convention:
> Nearly 15 cm is taken to draw a graphical scale.
English Graphical Scale
By convention:
> Nearly 6 inches is taken to draw a graphical scale.
Secondary Division Example
A 1-km division may be subdivided into:
100 m
500 m
250 m
200 m
depending on the required construction.
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9. 🧠 Competitive Exam One-Liners
Term Key Point
Scale Map–ground distance relationship
Map Distance Distance on map
Ground Distance Actual distance on ground
Numerator Represents map distance
Denominator Represents ground distance
R.F. Fractional/numerical scale
Statement Scale Written form
Graphical Scale Line/bar form
Bar Scale Same as graphical scale
Universal Method R.F.
Most important advantage of graphical scale Remains valid after enlargement/reduction
Simplest method Statement of Scale
R.F. 1 : 50,000 1 unit map = 50,000 same units ground
Metric system km, m, cm, mm
English system mile, furlong, yard, foot, inch
1 mile 8 furlongs
1 furlong 220 yards
1 yard 3 feet
1 foot 12 inches
1 km 1,000 m
1 m 100 cm
1 cm 10 mm
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