Representation of Geographical Features
Introduction
The Earth's surface is HUGE and COMPLEX. How do we REPRESENT it on a small piece of paper? Geographers use MAPS — a scaled-down REPRESENTATION of the Earth's surface on a flat surface. This chapter explores the DIFFERENT ways in which geographical features are SHOWN on maps.
1. What is a Map?
| Term | Definition |
|---|---|
| Map | A REPRESENTATION of the Earth's surface or a part of it on a FLAT surface |
| Globe | A THREE-DIMENSIONAL model of the Earth |
| Plan | A LARGE-SCALE map of a SMALL area (like a building or small neighbourhood) |
| Sketch | A ROUGH drawing of an area — NOT drawn to scale |
Map vs Globe
| Aspect | Map | Globe |
|---|---|---|
| Surface | FLAT | SPHERICAL |
| Accuracy | DISTORTED (especially near poles) | ACCURATE (true shape) |
| Portability | EASY to carry | BULKY |
| Detail | Can show LARGE detail of SMALL areas | Limited detail |
| Coverage | Can show ENTIRE world or PART | Shows ENTIRE Earth |
2. Types of Maps
Based on Scale
| Type | Scale | Use |
|---|---|---|
| Large-scale map | 1 cm = small distance (e.g., 1 cm = 1 km) | Shows SMALL areas in GREAT detail (city maps) |
| Small-scale map | 1 cm = large distance (e.g., 1 cm = 100 km) | Shows LARGE areas with LESS detail (world maps) |
Based on Content
| Type | Purpose | Example |
|---|---|---|
| PHYSICAL maps | Show NATURAL features — mountains, rivers, plains | Physical map of India showing Himalayas |
| POLITICAL maps | Show MAN-MADE boundaries — countries, states, capitals | Political map of India with state boundaries |
| THEMATIC maps | Show SPECIFIC information — population, rainfall, crops | Population density map |
3. Scale
What is Scale?
SCALE is the RATIO between distance on the map and the CORRESPONDING distance on the ground.
Example: Scale 1 cm = 1 km means 1 cm ON THE MAP = 1 km ON THE GROUND.
Types of Scale
(a) Verbal or Statement Scale
Expressed in WORDS:
- '1 centimetre = 1 kilometre'
- '2 cm on map = 1 km on ground'
(b) Representative Fraction (RF)
Expressed as a RATIO or FRACTION:
- 1 : 50,000 means 1 unit on map = 50,000 same units on ground
- 1 / 100,000 means 1 cm on map = 100,000 cm (1 km) on ground
IMPORTANT: The units on BOTH sides are the SAME. 1 : 50,000 means 1 cm = 50,000 cm (500 m or 0.5 km).
(c) Linear Scale (Graphical Scale)
A LINE drawn on the map, divided into DISTANCES (km, miles). It LOOKS like a ruler.
Advantage: Even if the map is ENLARGED or REDUCED, the linear scale REMAINS ACCURATE.
Converting Scale
| Conversion | Example |
|---|---|
| RF to Statement | 1 : 50,000 → 1 cm = 50,000 cm → 1 cm = 500 m → 1 cm = 0.5 km |
| Statement to RF | 1 cm = 5 km → 1 cm = 500,000 cm → RF = 1 : 500,000 |
Choosing the Right Scale
| For | Use |
|---|---|
| City map | Large scale (e.g., 1 : 10,000) |
| State map | Medium scale (e.g., 1 : 500,000) |
| World map | Small scale (e.g., 1 : 50,000,000) |
4. Conventional Signs and Symbols
Maps use STANDARDISED symbols to represent features. This makes maps READABLE in ANY language.
Types of Symbols
| Type | Feature | Examples |
|---|---|---|
| COLOUR | Natural features | Blue = water, Green = forests, Brown = mountains, Yellow = plains |
| POINT symbols | Specific locations | Dot = city, Triangle = mountain peak, Star = capital |
| LINE symbols | Linear features | Solid line = road, Dashed line = boundary, Wavy line = river |
| AREA symbols | Spreading features | Hatching = marsh/swamp, Dots = desert |
Common Conventional Signs
Water features: River (blue line), Lake (blue area), Well (circle with dot), Canal (blue line with dashes) Vegetation: Forest (green area with tree symbols), Scrubs (small dots), Cultivated land (patterns) Settlement: City (large shaded area), Village (small shaded area), Capital (star), Town (circle) Transport: Railway (thick line with bars), Road (double line), Bridge (symbol over river) Relief: Contour lines (brown), Spot height (dot with number), Triangulation point (triangle)
5. Contour Lines
What are Contour Lines?
CONTOUR lines are lines on a map that JOIN points of EQUAL HEIGHT above sea level.
Key Rules of Contours
- ALL points on a contour line have the SAME elevation
- CLOSE contours = STEEP slope
- WIDELY spaced contours = GENTLE slope
- Contours NEVER cross each other
- Contours form CIRCLES around hilltops
- EVERY 5th contour is a THICKER INDEX contour
Reading Landforms from Contours
| Landform | How Contours Look |
|---|---|
| Hill/Mountain | CLOSED circles, INCREASING elevation towards centre |
| Valley | V-shaped contours POINTING UPHILL (towards higher ground) |
| Ridge | ELONGATED closed contours |
| Plateau | CLOSED contours with a FLAT TOP |
| Escarpment | Contours very CLOSE together (steep drop) |
| Depression | HATCHED contours (short lines pointing towards the centre) |
| Saddle/Pass | Two HIGH areas with a LOW area between them |
Contour Interval
The VERTICAL difference between TWO successive contours.
- Example: If contour interval is 20 m, the lines are at 100 m, 120 m, 140 m, etc.
6. Topographic Maps
Topographic maps are LARGE-SCALE maps that show BOTH natural and man-made features in DETAIL. In India, these are prepared by the SURVEY OF INDIA.
Features of Topographic Maps
- Show RELIEF (through contours), DRAINAGE (rivers), VEGETATION, SETTLEMENTS, TRANSPORT
- Use CONVENTIONAL symbols
- Have a GRID system (Northings and Eastings) for location
- Include a SCALE and a LEGEND
Map Reading Skills
- Find DIRECTION (North is usually at the top)
- Identify FEATURES using conventional signs
- Calculate DISTANCE using the scale
- RELATE different features (e.g., why is the village near the river?)
ICSE Exam Focus
2-mark questions
- What is a MAP?
- What is the DIFFERENCE between a large-scale and small-scale map?
- What are CONTOUR lines?
4-mark questions
- Explain the THREE types of scale with examples.
- How do you DIFFERENTIATE between a steep slope and a gentle slope on a contour map?
- What are TOPOGRAPHIC maps? What features do they show?
6-mark (essay) questions
- Describe the DIFFERENT types of maps based on content and scale.
- Explain CONVENTIONAL symbols — why are they important in map reading?
Self-Test
-
What is the DIFFERENCE between a map and a globe? Answer: A map is a FLAT representation; a globe is SPHERICAL. Globes are MORE ACCURATE (no distortion) but less PORTABLE. Maps can show DETAILS of small areas; globes show the entire Earth.
-
How do you CONVERT an RF of 1 : 100,000 into a statement scale? Answer: 1 : 100,000 means 1 cm = 100,000 cm = 1,000 m = 1 km. So the statement scale is '1 cm = 1 km.'
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What is the ADVANTAGE of a LINEAR scale over a verbal scale? Answer: A linear scale REMAINS CORRECT even if the map is ENLARGED or REDUCED. A verbal scale becomes INCORRECT if the map size changes.
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What do CLOSE contour lines indicate? What about WIDELY spaced contours? Answer: CLOSE contours = STEEP slope. WIDELY spaced contours = GENTLE slope.
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Name THREE types of maps based on CONTENT. Answer: PHYSICAL maps (natural features), POLITICAL maps (boundaries), and THEMATIC maps (specific data like rainfall or population).
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Why are CONVENTIONAL SYMBOLS used on maps? Answer: They make maps INDEPENDENT of language — any person, regardless of their native language, can read the map. They also SAVE space and make maps CLEARER.
