Question 1

Choose the right answer from the four alternatives given below

(i) Remote sensing of objects can be done through various means such as A. remote sensors, B. human eyes and C. photographic system. Which of the following represents the true order of their evolution.

(a) ABC
(b) BCA
(c) CAB
(d) None of the above

(ii) Which of the following regions of Electromagnetic spectrum is not used in satellite remote sensing.

(a) Microwave region
(b) Infrared region
(c) X - rays
(d) Visible region

(iii) Which of the following is not used in visual interpretation technique?

(a) Spatial arrangements of objects
(b) Frequency of tonal change on the image
(c) Location of objects with respect to other objects
(d) Digital image processing

Accepted Answer

(i) Correct order of evolution is BCA.
Explanation: Initially, human eyes (B) were used for observation, followed by photographic systems (C), and then remote sensors (A) were developed for remote sensing.

(ii) X-rays (c) are not used in satellite remote sensing.
Explanation: Satellite remote sensing commonly uses microwave, infrared, and visible regions of the electromagnetic spectrum. X-rays are not used due to their high energy and absorption by the atmosphere.

(iii) Digital image processing (d) is not used in visual interpretation technique.
Explanation: Visual interpretation relies on spatial arrangements, tonal changes, and location of objects, whereas digital image processing is a computer-based technique. — Step-by-step solution:
(i) Evolution order:
- Human eyes (B) were the first means of observation.
- Photographic systems (C) came next with the invention of cameras.
- Remote sensors (A) are the latest technological advancement.
Hence, the correct order is BCA.

(ii) Satellite remote sensing uses electromagnetic spectrum regions that can penetrate the atmosphere and provide useful data. X-rays are absorbed by the atmosphere and are not used.

(iii) Visual interpretation techniques involve human analysis of images based on spatial arrangements, tonal variations, and object locations. Digital image processing is a computational method, not a visual interpretation technique.

Question 2

Answer the following questions in about 30 words.

(i) Why is remote sensing a better technique than other traditional methods?
(ii) Differentiate between IRS and INSAT series of satellites.
(iii) Describe in brief the functioning of pushbroom scanner.

Accepted Answer

(i) Remote sensing is better because it allows data collection over large areas quickly and repeatedly without physical contact, enabling monitoring of inaccessible or hazardous regions.

(ii) IRS (Indian Remote Sensing) satellites are primarily used for earth observation and resource management, whereas INSAT (Indian National Satellite System) satellites are mainly for communication, broadcasting, and meteorological services.

(iii) A pushbroom scanner uses a linear array of detectors to scan the ground perpendicular to the satellite's motion, capturing data line by line as the satellite moves forward. — Step-by-step solution:
(i) Remote sensing advantages include wide area coverage, repetitive data acquisition, and non-intrusive data collection compared to traditional ground surveys.

(ii) IRS satellites focus on imaging and remote sensing applications; INSAT satellites focus on communication and weather forecasting.

(iii) Pushbroom scanners have a linear detector array that captures a swath of the Earth's surface simultaneously as the satellite moves, improving data quality and reducing mechanical complexity.

Question 3

Answer the following questions in about 125 words.

(i) Describe the operation of a whiskbroom scanner with the help of a diagram. Explain how it is different from pushbroom scanner.
(ii) Identify and list the changes that can be observed in the vegetation of Himalayas (Fig.6.9).

Accepted Answer

(i) A whiskbroom scanner uses a rotating mirror to scan the ground across the satellite's flight path. It collects data point by point or line by line by sweeping the detector's field of view across the swath. The detector receives reflected radiation from the ground as the mirror oscillates. This method allows high spatial resolution but involves moving parts.

Difference from pushbroom scanner: Pushbroom scanners use a linear array of detectors that simultaneously capture an entire line of data perpendicular to the flight path without moving parts, resulting in better reliability and signal-to-noise ratio.

(ii) Changes in Himalayan vegetation include variations in vegetation types with altitude, seasonal changes in foliage density, and impact of climatic factors. There may be a decrease in vegetation density at higher altitudes and changes in species composition due to environmental gradients. — Step-by-step solution:
(i) Whiskbroom scanner operation:
- Uses a rotating mirror to scan across track.
- Detector collects reflected energy sequentially.
- Produces high-resolution images but mechanical parts may wear.

Pushbroom scanner:
- Uses linear detector array.
- No moving mirror.
- Simultaneous data capture along a line.

(ii) Vegetation changes in Himalayas:
- Altitudinal zonation affects vegetation types.
- Seasonal variations cause changes in greenness.
- Environmental stresses influence species distribution.

Question 4

ACTIVITY

Identify various features marked on IRS IC LISS III imagery shown below. Draw clues from the description of the elements of image interpretation discussed and the colours in which various objects appear on a Standard False Colour Composite.

Accepted Answer

To identify features on IRS IC LISS III imagery:
- Use knowledge of image interpretation elements such as tone, texture, pattern, shape, size, shadow, and association.
- Recognize that in a Standard False Colour Composite, vegetation appears red due to near-infrared reflectance.
- Water bodies appear dark or black.
- Urban areas appear in shades of cyan or blue.
- Agricultural fields show distinct patterns and textures.
- Use these clues to label features such as forests, water bodies, urban settlements, and agricultural lands on the image. — Step-by-step solution:
- Analyze the colors in the false color composite.
- Identify red areas as dense vegetation.
- Identify dark areas as water bodies.
- Identify blue/cyan areas as urban or built-up regions.
- Look for patterns and shapes to distinguish agricultural fields.
- Use spatial association and location to confirm feature identification.

Question 5

What is the definition of remote sensing?

Accepted Answer

Remote sensing is the total process used to acquire and measure information about some property of objects or phenomena by a recording device (sensor) that is not in physical contact with the objects or phenomena under study. For example, satellites use sensors to collect data about Earth's surface without touching it. — Remote sensing involves collecting information about objects or phenomena from a distance using sensors that do not physically contact the objects. This allows the study of Earth's surface features and phenomena remotely, which is useful in geography and environmental monitoring.

Question 6

Which of the following is NOT a component of the conceptual framework of remote sensing?

Accepted Answer

Physical contact between sensor and object — Remote sensing specifically involves collecting information without physical contact between the sensor and the object. The three main components are the sensor, the energy waves, and the object surface.

Question 7

What is absorptance in remote sensing?

Accepted Answer

Absorptance — Absorptance is defined as the ratio of the radiant energy absorbed by a substance to the energy it receives. It indicates how much energy an object absorbs compared to what it receives.

Question 8

Which term describes the specific wavelength interval in the electromagnetic spectrum used in remote sensing?

Accepted Answer

Band — A band refers to a specific wavelength interval in the electromagnetic spectrum. Remote sensing sensors detect energy in different bands to analyze various surface features.

Question 9

What is a Digital Number (DN) in the context of remote sensing images?

Accepted Answer

A Digital Number is the intensity value of a pixel in a digital image. For example, each pixel in a satellite image has a DN representing the brightness or reflectance of that location. — Digital Numbers represent the recorded intensity of electromagnetic radiation at each pixel in a digital image. These values are used in processing and interpreting remote sensing data.

Question 10

Which of the following best describes the Electromagnetic Spectrum?

Accepted Answer

The range of wavelengths from radio waves to gamma rays — The Electromagnetic Spectrum is the continuum of electromagnetic radiation ranging from long wavelength radio waves to short wavelength gamma rays. Remote sensing uses parts of this spectrum.

Question 11

Explain the process of 'Interaction of Energy with the Earth's Surface' in remote sensing.

Accepted Answer

Interaction of energy with Earth's surface involves absorption, reflection, transmission, or emission of energy by objects. For example, fresh water absorbs more energy in red and infrared regions and appears dark in satellite images, while turbid water reflects more blue and green light appearing lighter. — When electromagnetic energy reaches Earth's surface, it interacts differently with various objects depending on their properties. This interaction determines how the objects appear in remote sensing images and helps in their identification.

Question 12

Which atmospheric constituents absorb energy in the middle infrared region, affecting remote sensing data?

Accepted Answer

Carbon dioxide (CO2), Hydrogen (H), and water molecules — CO2, hydrogen, and water vapor absorb energy in the middle infrared region, which can reduce the energy reaching the sensor and affect image quality.

Question 13

Describe the difference between Sun-Synchronous and Geostationary satellites in terms of their orbits and uses.

Accepted Answer

Sun-Synchronous satellites orbit at 700-900 km altitude in near-polar orbits, passing over the same area multiple times daily, used mainly for Earth resource applications. Geostationary satellites orbit at about 36,000 km over the equator, remain fixed relative to Earth, and are used for telecommunication and weather monitoring. — Sun-Synchronous satellites provide consistent lighting conditions for imaging by passing over the same area regularly, while Geostationary satellites provide continuous coverage over a fixed area, suitable for weather and communication.

Question 14

What is the primary difference between photographic and non-photographic sensors in remote sensing?

Accepted Answer

Photographic sensors capture images instantaneously on film; non-photographic sensors collect data bit-by-bit digitally. — Photographic sensors (cameras) record images at once on film, while non-photographic sensors (scanners) collect data sequentially in digital form, allowing detailed spectral analysis.

Question 15

Explain the working principle of a whiskbroom scanner used in satellite remote sensing.

Accepted Answer

A whiskbroom scanner uses a rotating mirror and a single detector to sweep across the field of view, collecting data in narrow spectral bands line by line. The rotating mirror oscillates through an angular field, directing reflected energy to the detector for conversion into electrical signals. — The whiskbroom scanner scans the ground by oscillating a mirror that directs energy to a single detector, which records data sequentially across the swath, creating an image line by line.

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Introduction To Remote Sensing — Study Notes

Introduction To Remote Sensing

Glossary

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Practice Questions — Introduction To Remote Sensing

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