Topographical Sheets: Colours, Signs and Symbols
ICSE Class 7 · Geography · Chapter 1
What this chapter covers
- What a topographical sheet is
- The Survey of India and its sheets
- Why maps use colours
- Blue, red and yellow
- Brown and green
- Conventional signs and symbols
- Reading features on a toposheet
Key definitions
Natural features are the parts of the landscape that nature has made, such as hills, valleys, rivers, lakes, sand dunes and forests.
Human-made features are the things people have built or shaped, such as villages, towns, roads, railway lines, canals, wells, bridges, temples and post offices.
Relief is the difference in height between high and low parts of the land, such as hills, plateaus, valleys and plains.
Conventional signs and symbols are the standard marks, small pictures, lines and letters that are used on maps to show particular features, and that have the same meaning for every reader.
Key points
- A topographical sheet, or toposheet, is a detailed, large-scale map of a small area showing natural and human-made features.
- In India, toposheets are prepared by the Survey of India, set up in 1767, with its headquarters at Dehradun.
- The country is divided into numbered sheets that fit edge to edge; the margin gives the sheet number, scale, north arrow and key.
- North is towards the top of a toposheet; eight directions are used to describe where features lie.
- Blue shows water bodies, red shows settlements and roads, and yellow shows agricultural land.
- Brown shows high relief and sand features, and green shows forests, scrub and orchards.
- Black is used for railways, boundaries and many names; white areas show uncultivated land.
- Conventional signs and symbols are standard marks with the same meaning on every sheet; they may be point, line or area symbols.
- Letters such as PO, PS, RH, DB, CH and BM mark useful buildings and survey points.
- To read a sheet, start with the margin and key, then trace the colours, water, settlements and transport lines, and describe the area using directions.
Questions answered
What is a topographical sheet?
A topographical sheet is a detailed, large-scale map of a small area that shows both the natural and the human-made features of the land.
Which organisation prepares the official toposheets of India, and where is its headquarters?
The Survey of India prepares them; its headquarters are at Dehradun.
Name the colour used on a toposheet for each of these: (a) a canal, (b) a village, (c) fields of wheat, (d) a hill, (e) a teak forest.
(a) Blue, (b) red, (c) yellow, (d) brown, (e) green.
Why are colours used on a toposheet?
Colours separate one group of features from another at a glance, so a crowded map stays clear, quick to read and free from confusion.
What does the word "conventional" mean in "conventional signs and symbols", and why does it matter?
It means agreed upon by everyone. Because all sheets use the same symbols, a reader can understand any sheet in the country once the symbols are learnt.
What do the letters PO, PS, RH and BM stand for on a toposheet?
Post office, police station, rest house and benchmark.
How would you tell a metalled road from an unmetalled road on a toposheet?
A metalled road is a filled double red line; an unmetalled road is a double broken red line.
How is a perennial river shown differently from a non-perennial river?
A perennial river is drawn in solid blue because it always has water; a non-perennial river often shows a blue outline with dots or sand inside, because its bed is dry for part of the year.