GeographyCBSE Class 11 · Topographical Maps

Topographical Maps, Relief Methods, Contours and Slopes (Class 11 Practical Work in Geography, Chapter 5)

Updated 17 October 2026 · Fact-checked

Topographical maps are general-purpose, relatively large-scale base maps prepared in series by the Survey of India (1:250,000, 1:50,000, 1:25,000 among others). Relief is shown by hachures, hill shading, layer tints, spot heights and, mainly, contours, which join places of equal height. Close contours show steep slopes and wide contours gentle slopes; gradient = vertical interval / horizontal equivalent.

Understand Topographical Sheets of the Survey of India, Methods of Showing Relief, Contours and Types of Slope

Why this topic matters. This chapter carries 4 marks in the 30-mark practical exam; the syllabus covers 1:50,000 or 1:25,000 sheets, conventional symbols and contour interpretation. Slope identification and gradient sums are regular questions.

1. What they are. General-purpose maps at relatively large scales showing relief, vegetation, water bodies, cultivated land, settlements and transport. They serve as base maps for all other maps. In India the Survey of India prepares them in series, in which all sheets share the same reference point, scale, projection, conventional signs, symbols and colours.

2. Two series. The India and Adjacent Countries Series was prepared until the Delhi Survey Conference of 1937; afterwards only India was mapped, to International Map Series specifications, keeping the old numbering and layout. The International Map Series of the World has standard maps at 1:1,000,000 and 1:250,000.

3. Scales and coverage. 1:1,000,000 covers 4 x 4 degrees; 1:250,000 covers 1 x 1 degree; 1:125,000 covers 30 x 30 minutes; 1:50,000 covers 15 x 15 minutes; 1:25,000 covers 5 x 7 minutes 30 seconds.

4. Relief. The elevations and depressions of the surface. Methods: hachures (short lines along the direction of maximum slope), hill shading, layer tints, benchmarks and spot heights and contours. Topographical maps mainly use contours and spot heights.

5. Contours. Imaginary lines joining places of equal elevation above mean sea level. The vertical interval (VI) is the height difference between successive contours (for example 20, 50 or 100 m) and is constant on a map. The horizontal equivalent (HE) is the horizontal distance between contours; it is large on gentle slopes and small on steep slopes. Features: closely spaced contours mean steep slope, widely spaced mean gentle slope, merging contours show vertical slopes (cliffs, waterfalls), and contours of different heights do not cross.

6. Gradient. Gradient = VI / HE in the same units, often written 1 in n.

7. Types of slope. Gentle: contours far apart. Steep: contours close. Concave: gentle in the lower part and steep in the upper part, so wide spacing at the bottom and close spacing at the top. Convex: gentle in the upper part and steep in the lower part, so wide spacing at the top and close spacing at the bottom.

Topographical Sheets of the Survey of India, Methods of Showing Relief, Contours and Types of Slope: key facts

Sheet coverage: $1 : 1, 000, 000 : 4 x 4 d e g r ees ∣1 : 250, 000 : 1 x 1 d e g r ee ∣1 : 125, 000 : 30 x 30 min u t es ∣1 : 50, 000 : 15 x 15 min u t es ∣1 : 25, 000 : 5 x 7 min u t es 30 seco n d s$; Survey of India.
Contour terms: $V I : h e i g h t d i f f er e n ce, co n s t an t ∣ H E : h or i z o n t a l d i s t an ce, v a r i es ∣ G r a d i e n t = V I / H E$; Same units.
Slopes: Gentle wide spacing
Steep close spacing
Concave close at top
Convex close at bottom; Contour pattern.
Relief methods: Hachures
Hill shading
Layer tints
Benchmarks and spot heights
Contours; Contours main method.

Gentle	wide spacing
Steep	close spacing
Concave	close at top
Convex	close at bottom

How to answer Topographical Sheets of the Survey of India, Methods of Showing Relief, Contours and Types of Slope questions

Gradient sums need equal units.

1Write VI in metres and HE in metres.
2Convert map distance to ground distance using the scale.
3Gradient = VI / HE; write as 1 in n by dividing.
4State the slope type from the spacing.

Topographical Sheets of the Survey of India, Methods of Showing Relief, Contours and Types of Slope in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Hill path

Suppose a village path crosses a slope where the contours are packed very close together near the top and spread out near the bottom.

What type of slope is this?

Try it first, then show the solutionSolution

Close at the top, wide at the bottom.
That is a concave slope (steep above, gentle below).

Answer: A concave slope.

Memory hook: Close top, concave.

Water tank site

Suppose an engineer reads a map with a contour interval of 20 m and finds two contours only 400 m apart on the ground.

What is the gradient?

Try it first, then show the solutionSolution

VI = 20 m, HE = 400 m.
20 / 400 = 1 in 20.

Answer: A gradient of 1 in 20.

Memory hook: VI over HE.

Tricks to remember Topographical Sheets of the Survey of India, Methods of Showing Relief, Contours and Types of Slope

Short memory aids. Say each one aloud once, then use it on a question the same day.

Close is steep
Close contours steep, wide contours gentle
Use it when: Slope.
Concave closes at the top
Convex closes at the bottom
Use it when: Slope types.
VI constant, HE varies
Vertical interval fixed, horizontal equivalent changes
Use it when: Contour terms.

Topographical Sheets of the Survey of India, Methods of Showing Relief, Contours and Types of Slope: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Steep slope · 1 mark · MCQBoard level

A steep slope is shown on a contour map by:
(A) widely spaced contours
(B) closely spaced contours
(C) no contours
(D) dotted contours

Try it first, then show the solutionSolution

Close contours show steep slopes (1 mark).

Answer: (B)

Example 2: Define contour · 2 marks · Very short answerBoard level

Define a contour and the vertical interval. (2 marks)

Try it first, then show the solutionSolution

Contour: line joining places of equal elevation above mean sea level (1 mark).
VI: height difference between successive contours (1 mark).

Answer: A contour is an imaginary line joining places of equal height above mean sea level. The vertical interval is the constant difference in height between successive contours.

Example 3: Gradient sum · 3 marks · Short answerHarder board level

On a 1:50,000 map two contours with a vertical interval of 50 m are 2 cm apart. Find the ground distance and the gradient. (3 marks)

Try it first, then show the solutionSolution

2 cm x 50,000 = 100,000 cm = 1,000 m (1 mark).
Gradient = 50 / 1,000 (1 mark).
= 1 in 20 (1 mark).

Answer: Ground distance = 2 x 50,000 = 100,000 cm = 1,000 m. Gradient = VI / HE = 50 / 1,000 = 1 in 20.

Example 4: Assertion and reason: merging contours · 1 mark · Assertion-reasonHarder board level

Assertion (A): Contours merging into one line show a cliff.
Reason (R): A cliff is a nearly vertical slope with almost no horizontal distance between heights.
(A) Both true, R explains A
(B) Both true, R does not explain A
(C) A true, R false
(D) A false, R true

Try it first, then show the solutionSolution

Very small HE on a vertical face makes contours merge (1 mark).

Answer: (A)

Example 5: HOTS: sheet coverage · 5 marks · Long answerHOTS / competency

A 1:250,000 sheet covers 1 x 1 degree and a 1:50,000 sheet covers 15 x 15 minutes. Find how many 1:50,000 sheets fit in a 1:250,000 sheet, how many 1:250,000 sheets fit in a 1:1,000,000 sheet (4 x 4 degrees), and the east-west side of a 1:50,000 sheet in cm at that scale if its ground width is about 26 km. (5 marks)

Try it first, then show the solutionSolution

1 degree = 60 minutes; 60 / 15 = 4 sheets along each side (1 mark).
4 x 4 = 16 sheets of 1:50,000 per 1:250,000 sheet (1 mark).
4 / 1 = 4 along each side, so 16 sheets of 1:250,000 in a 1:1,000,000 sheet (1 mark).
Width = 26 km = 2,600,000 cm (1 mark).
2,600,000 / 50,000 = 52 cm (1 mark).

Answer: Since 1 degree = 60 minutes and a 1:50,000 sheet spans 15 minutes, 60 / 15 = 4 sheets fit along each side, so 4 x 4 = 16 sheets fit in one 1:250,000 sheet. A 1:1,000,000 sheet spans 4 degrees against 1 degree, so 4 x 4 = 16 sheets of 1:250,000 fit in it. If the ground width is about 26 km (an assumed illustrative figure), the sheet width is 2,600,000 cm / 50,000 = 52 cm.

Where students lose marks in Topographical Sheets of the Survey of India, Methods of Showing Relief, Contours and Types of Slope

The slips examiners see most often, and what to write instead.

Mistake: Using different units in gradient
Map cm with VI in m.
Wrong working
Gradient = 50 / 2.
Right working
Convert HE to metres first: 1,000 m; 50 / 1,000 = 1 in 20.
Do this: Make units the same.
Usually costs: 1 mark.
Mistake: Reversing concave and convex
Terms mixed.
Wrong working
Concave has close contours at the bottom.
Right working
Concave: close at the top; convex: close at the bottom.
Do this: Learn with the bottom for convex.
Usually costs: 1 mark.
Mistake: Saying contours join places of equal slope
Word slip.
Wrong working
Contours join places of equal gradient.
Right working
Contours join places of equal height above mean sea level.
Do this: Use "height".
Usually costs: 1 mark.

Exam tips

Show VI, HE and the units in every gradient sum.
Use a sketch of contour spacing for slope types.
Quote sheet coverage for 1:50,000 as 15 x 15 minutes.

Practice questions on Topographical Sheets of the Survey of India, Methods of Showing Relief, Contours and Types of Slope

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
The India and Adjacent Countries Series was prepared until the:
(A) 1937 Delhi Survey Conference
(B) 1767 survey
(C) 1947 partition
(D) 1957 metric change
Hint
Delhi Survey Conference.
Answer
(A)
Q2 · 2 marks · Very short answerBoard level
Name any four methods of showing relief on maps. (2 marks)
Hint
Hachures to contours.
Answer
Hachures, hill shading, layer tints, benchmarks and spot heights, and contours.
Q3 · 3 marks · Short answerHarder board level
Distinguish between concave and convex slopes with the contour pattern of each. (3 marks)
Hint
Top and bottom.
Answer
A concave slope is gentle in the lower part and steep in the upper part, so contours are widely spaced at the bottom and close at the top. A convex slope is gentle in the upper part and steep in the lower part, so contours are widely spaced at the top and close at the bottom.
Q4 · 3 marks · Short answerHarder board level
Explain horizontal equivalent and its relation to slope. (3 marks)
Hint
Small on steep slopes.
Answer
The horizontal equivalent is the horizontal distance between successive contours. It is large on gentle slopes and small on steep slopes, so closely spaced contours show a steep slope.
Q5 · 4 marks · Short answerHOTS / competency
On a map with a contour interval of 20 m, the contours near a village are 1.25 cm apart on a 1:25,000 map. Find the ground distance, the gradient, and say whether the slope is gentle or steep compared with 1 in 10. (4 marks)
Hint
Convert cm.
Answer
Ground distance = 1.25 x 25,000 = 31,250 cm = 312.5 m. Gradient = 20 / 312.5 = 1 in 15.6 (about 1 in 16). A gradient of 1 in 10 is steeper, so this slope is gentler than 1 in 10.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.What are base maps?Show answer
Topographical maps used to prepare all other maps.
2.Which agency makes the sheets?Show answer
Survey of India.
3.How much does a 1:25,000 sheet cover?Show answer
5 x 7 minutes 30 seconds.
4.What does constant VI mean?Show answer
Equal height difference between successive contours.

Topographical Sheets of the Survey of India, Methods of Showing Relief, Contours and Types of Slope: frequently asked questions

What is a spot height?

A point marked with its height above sea level.

What are hachures?

Short lines drawn along the direction of maximum slope.

Do contours of different heights cross?

Usually not.