Notes: Representation of Geographical Features

Notes: Representation of Geographical Features

Easy Explanation - Class 7 Geography

1. Why Do We Need Maps and Symbols?

Simple point: The Earth is huge. We can't draw it full size on paper. So we make maps.

  • Map = A small drawing of the Earth that gives us info about places.
  • But we can't draw real mountains, rivers, or houses on a map. There isn’t enough space.
  • Solution: We use Symbols and Signs. Every symbol has a fixed meaning.
  • Example: Anamika’s father was an architect. He also made maps of a shopping mall using symbols. Geography does the same thing.

History Point: The Greeks were the first to use maths for map-making. Anaximander believed the Earth was cylindrical and made a world map.

2. What is a Topographical Map?

Topo Map = The most detailed map of the Earth

  1. Who makes it: Survey of India makes these maps.
  2. Scale: Mostly 1 : 50,000 scale is used. That means 1 cm on the map = 50,000 cm on the ground = 500 m = 0.5 km
  3. What it shows: 2 types of features
    • Natural: Mountains, rivers, forests - made by nature
    • Man-made: Roads, bridges, dams, houses - made by humans
  4. It is 2D: Shows length and width, not height. But contours give an idea of height.
DID YOU KNOW: Mount Everest is named after Colonel Sir George Everest. He was Surveyor General of India from 1830 to 1843.

3. How to Find Places on a Topo Map? Grid System

A map has a net of straight lines. This is called a Grid.

  1. There are 2 Axes:
    • X-axis = Horizontal = Goes from Left to Right
    • Y-axis = Vertical = Goes from Bottom to Top
  2. Rule: Always write the X number first, then Y. Like (79, 86)
  3. Benefit: You can tell the exact location of any well, temple, or bridge.

4. What Do Colours Mean on a Topo Sheet?

Topo maps "talk" through colours. Each colour has its own language:

Colour What it Shows Trick to Remember
Black Names, boundaries, railway, phone lines "Black = Basic info"
Blue Water - rivers, ponds, wells, seas "Blue = B for Blue water"
Green Forests, trees, orchards "Green = Grass/Trees"
Yellow Cultivated area / farmland "Yellow = Yellow mustard fields"
Brown Contours, height, sand dunes "Brown = Bhoomi/Soil"
Red Settlements, roads, buildings "Red = Residential areas"

5. How to Measure Distance on a Map? Scale

A map is small, the Earth is big. So we need to show the ratio between map and Earth. This is called Scale.

3 Types of Scale:

  1. Statement Scale / Verbal Scale
    • Written in words.
    • Ex: 2 cm : 7 km means 2 cm on map = 7 km on ground
  2. Representative Fraction (R.F.)
    • Written as a fraction. No units are written.
    • Formula: R.F. = Map Distance / Ground Distance
    • Ex: 1 : 50,000 means 1 unit on map = 50,000 units on ground
    • Converting: 1 cm : 5,00,000 cm → in metres = 1 cm : 5,000 m = 1 cm : 5 km
  3. Graphic / Linear Scale
    • A scale bar drawn on the map, like a ruler.
    • Best one: Even if the map is photocopied and size changes, this scale stays correct.
    • Parts: Primary Divisions and Secondary Divisions

Map Distance vs Ground Distance

  • Map Distance: Distance measured with a ruler in cm.
  • Ground Distance: Real distance on Earth in km.

6. Two Ways to Measure Distance on a Map

  1. Straight-line Distance = Direct Distance
    • Measure with a ruler. A straight line between two points.
    • Use: For aeroplane routes.
    • Steps: Place ruler → measure cm → convert to km using scale.
  2. Curved-line Distance = Indirect Distance
    • For winding paths like roads or rivers.
    • How to measure: Use a thread or an Opisometer.
    • Steps: Place thread along the path → straighten it and measure with ruler → convert to km using scale.

7. Conventional Signs and Symbols

We don’t draw real objects on maps. We use standard signs that are same all over the world.

Why needed:

  1. Saves space.
  2. Everyone understands them, no language problem.
  3. Key/Legend on the map explains all signs.

Some Important Signs:

  • = = → Metalled Road
  • - - - → Unmetalled Road
  • +-+-+ → Railway line
  • ⏊⏊ → Temple
  • ✝ → Church
  • + → Hospital
  • PO → Post Office
  • ● → Well
  • △ → Triangulated Height

Quick Revision - Remember in 1 Min

  1. Topo Map = Made by Survey of India, 1:50,000 scale, shows natural + man-made features.
  2. Colours: Blue=Water, Green=Forest, Yellow=Farms, Brown=Height, Red=Settlement, Black=Names.
  3. 3 Types of Scale: Statement, R.F., Graphic. Graphic is most reliable.
  4. R.F. Formula: Map Distance / Ground Distance. Never write units.
  5. Distance: Straight = Ruler, Curved = Thread/Opisometer.
  6. Grid: X first, then Y. Used to locate places.
  7. Symbols: Check the Key/Legend. Same symbols are used worldwide.
Tip: Look at a topo sheet carefully. The colour that covers the most area tells you what’s common there. If there’s more Yellow = it’s a farming area.