CBSE Class 11 Geography Chapter 7: Introduction to Remote Sensing NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 11 PDF

This chapter, "Introduction to Remote Sensing," for CBSE Class 11 Geography, provides essential knowledge about acquiring information about the Earth's surface without direct physical contact. The NCERT Solutions cover the fundamental principles of remote sensing, including the evolution of sensing technologies from human eyes to sophisticated photographic and remote sensor systems. It delves into the electromagnetic spectrum used in satellite remote sensing, differentiating it from regions like X-rays that are not utilized. The solutions also explain the techniques of visual interpretation and the functioning of different types of scanners, such as whiskbroom and pushbroom scanners, highlighting their operational differences. Furthermore, it touches upon the application of remote sensing in observing environmental changes, like vegetation patterns in the Himalayas. These solutions are designed to help students grasp the core concepts, understand the technological advancements, and prepare effectively for their examinations by offering clear explanations and structured answers.

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Quick info

Board	CBSE
Class	Class 11
Subject	Geography
Session	2026
Language	English
Type	NCERT Solutions
Chapter	7. Introduction to Remote Sensing

Chapter summary

Chapter 7, "Introduction to Remote Sensing," for Class 11 Geography, focuses on the principles and applications of acquiring data about Earth's features from a distance. The NCERT Solutions explain the historical development of remote sensing tools, the electromagnetic spectrum's role, and the distinction between various sensing regions. It clarifies visual interpretation techniques and details the mechanics of whiskbroom and pushbroom scanners, emphasizing their operational differences. The chapter also illustrates how remote sensing aids in observing environmental phenomena, such as vegetation changes. These solutions provide a clear understanding of the foundational aspects of remote sensing for students.

Learning outcomes

Understand the evolution of remote sensing technologies.
Identify the regions of the electromagnetic spectrum used in satellite remote sensing.
Differentiate between IRS and INSAT satellite series.
Explain the functioning of whiskbroom and pushbroom scanners.
Recognize the application of remote sensing in observing environmental changes.

Topics covered

Paper topics

Introduction to Remote Sensing
Evolution of Remote Sensing Techniques
Electromagnetic Spectrum in Remote Sensing
Satellite Series (IRS, INSAT)
Visual Interpretation Techniques
Whiskbroom Scanner
Pushbroom Scanner
Application in Vegetation Analysis
Data Collection Methods
Comparison of Sensing Techniques

Important topics

Evolution of Remote Sensing Technologies
Electromagnetic Spectrum Usage
Whiskbroom vs. Pushbroom Scanners
IRS vs. INSAT Satellites
Visual Interpretation Elements

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Questions and Solutions

Question 1 (i)

Choose the right answer from the four alternatives given below. Remote sensing of objects can be done through various means such as remote sensors, human eyes, and photographic systems. Which of the following represents the true order of their evolution?

(a) ABC

(b) BCA

(d) None of the above

Solution: The evolution of remote sensing technologies began with the most basic form of observation, which is the human eye. Subsequently, photographic systems were developed, allowing for the capture of images. The most advanced stage involves sophisticated remote sensors, often mounted on satellites or aircraft, which can detect and record electromagnetic radiation across various spectrums. Therefore, the correct order of evolution is Human Eyes (B), Photographic System (C), and Remote Sensors (A). This corresponds to the sequence BCA.

Question 1 (ii)

Choose the right answer from the four alternatives given below. Which of the following regions of the Electromagnetic spectrum is not used in satellite remote sensing?

(a) Microwave region

(b) Infrared region

(d) Visible region

Solution: Satellite remote sensing relies on detecting electromagnetic radiation reflected or emitted from the Earth's surface. The commonly used regions of the electromagnetic spectrum for this purpose are the visible region, the infrared region, and the microwave region. X-rays, however, are a form of high-energy radiation and are not typically used in standard satellite remote sensing applications due to their properties and the specialized equipment required to detect them, as well as potential safety concerns.

Question 1 (iii)

Choose the right answer from the four alternatives given below. Which of the following is not used in visual interpretation technique?

(a) Spatial arrangements of objects

(b) Frequency of tonal change on the image

(d) Digital image processing

Solution: Visual interpretation of remote sensing imagery involves analyzing various elements directly from the image. These elements include the spatial arrangement of objects (how they are positioned relative to each other), their location with respect to other features, shape, size, texture, and tone. Digital image processing, on the other hand, is a separate set of computational techniques used to manipulate and analyze digital image data, often as a precursor to or alternative to visual interpretation. Therefore, digital image processing is not a component of the visual interpretation technique itself.

Question 2 (i)

Answer the following questions in about 30 words. Why is remote sensing a better technique than other traditional methods?

Solution: Remote sensing is superior to traditional methods for collecting geo-spatial information because it allows data acquisition about Earth's surface features (like crops, soil, water) without physical contact. It is more efficient, less time-consuming, and practical for large areas where ground surveys are difficult or expensive.

Question 2 (ii)

Answer the following questions in about 30 words. Differentiate between IRS and INSAT series of satellites.

Solution: The IRS (Indian Remote Sensing) satellite series operates at lower altitudes (700-900 km) and provides detailed imagery for resource mapping and navigation services over India. In contrast, the INSAT (Indian National Satellite) system consists of multipurpose geostationary satellites orbiting at approximately 36,000 km, used for telecommunications, broadcasting, meteorology, and search and rescue operations.

Question 2 (iii)

Answer the following questions in about 30 words. Describe in brief the functioning of push broom scanner.

Solution: A push broom scanner uses a linear array of many detectors, each corresponding to a pixel. As the satellite moves, these detectors collect reflected energy from the ground simultaneously across the sensor's swath, building the image line by line without a scanning mirror.

Question 3 (i)

Answer the following questions in about 125 words. Describe the operation of a whiskbroom scanner with the help of a diagram. Explain how it is different from pushbroom scanner.

Solution: A whiskbroom scanner operates by using a mirror that sweeps across the sensor's field of view, perpendicular to the satellite's direction of travel. This mirror reflects incoming radiation from a single ground resolution cell (pixel) onto a single detector. The detector measures the energy, and as the mirror sweeps, it collects data one pixel at a time, building up the image line by line. The mirror's motion covers a specific angular range (e.g., 90° to 120°) to capture data across the swath.

The primary difference between a whiskbroom scanner and a pushbroom scanner lies in their detection mechanism. A whiskbroom scanner uses a single detector and a moving mirror to scan across the scene. Conversely, a pushbroom scanner employs a linear array of numerous detectors, where each detector is aligned to capture energy from a specific ground cell simultaneously. This array captures an entire line of pixels at once, eliminating the need for a scanning mirror and generally resulting in higher spatial resolution and efficiency.

Question 3 (ii)

Answer the following questions in about 125 words. Identify and list the changes that can be observed in the vegetation of Himalayas.

Solution: Remote sensing imagery, such as that from the IRS satellite, can reveal significant changes in Himalayan vegetation between different seasons. For instance, images taken in May might show extensive coniferous vegetation, typically appearing as distinct red patches due to their spectral reflectance properties in certain bands. When comparing this with an image from November, additional red patches may indicate the presence of deciduous vegetation, which sheds its leaves seasonally. Furthermore, lighter red hues in the November image could correspond to rabi crops, highlighting the seasonal agricultural activities in the plains adjacent to the Himalayas. This demonstrates how remote sensing aids in monitoring vegetation cover and agricultural patterns.

Common mistakes

Confusing the order of evolution of remote sensing techniques.
Incorrectly identifying regions of the electromagnetic spectrum used in satellite sensing.
Failing to distinguish between the operational mechanisms of whiskbroom and pushbroom scanners.
Misinterpreting the application of remote sensing for observing specific environmental changes.

Revision tips

Focus on the chronological order of remote sensing tool development.
Memorize the electromagnetic spectrum regions relevant to satellite sensing.
Clearly understand and compare the working principles of whiskbroom and pushbroom scanners.
Review the examples of remote sensing applications, like observing Himalayan vegetation.

Practice MCQs

Q1. What is the correct chronological order of the evolution of remote sensing methods?

Q2. Which part of the electromagnetic spectrum is NOT typically used in satellite remote sensing?

Q3. Which of the following is NOT a factor considered in visual interpretation techniques for remote sensing images?

Q4. What is a key characteristic of the IRS satellite series?

Q5. How does a push broom scanner differ from a whiskbroom scanner?

Frequently asked questions

What is remote sensing?

Remote sensing is a technique used to gather information about objects or phenomena on the Earth's surface from a distance, without making physical contact. This is typically done using sensors on satellites or aircraft.

Why is remote sensing considered better than traditional methods?

Remote sensing is more efficient for large-scale data collection, providing information about spatial distribution and object properties quickly and often more cost-effectively than traditional ground surveys, which can be time-consuming and impractical for vast areas.

What are the main types of scanners discussed in this chapter?

The chapter discusses two main types of scanners: whiskbroom scanners, which use a scanning mirror and a single detector to capture data pixel by pixel, and pushbroom scanners, which use a linear array of detectors to capture multiple pixels simultaneously.

Which parts of the electromagnetic spectrum are used in satellite remote sensing?

Satellite remote sensing commonly utilizes the microwave, infrared, and visible regions of the electromagnetic spectrum. Regions like X-rays are generally not used.

What is the difference between IRS and INSAT satellites?

IRS satellites operate at lower altitudes (700-900 km) and are primarily used for remote sensing and navigation over India. INSAT satellites are geostationary (around 36,000 km altitude) and serve multipurpose functions like telecommunications, broadcasting, and meteorology.

How can remote sensing help observe vegetation changes?

By comparing satellite images taken at different times (e.g., May and November), remote sensing can reveal changes in vegetation types, such as the presence of coniferous versus deciduous forests or different types of crops, by analyzing spectral signatures like red patches.

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