Introduction to Remote Sensing


EXERCISE

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

Ans: (c) CAB.

(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

Ans:  (c) X-rays.

(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

Ans: 

2. Answer the following questions in about 30 words.

 (i) Why is remote sensing a better technique than other traditional methods?

Ans: Here are some key reasons why remote sensing often outperforms traditional methods:

*Wider coverage: It can quickly map and analyze vast areas inaccessible on foot.

*Detailed data: Provides detailed, objective data like spectral information beyond human vision.

*Real-time monitoring: Enables near-real-time monitoring of dynamic changes like deforestation or pollution.

*Cost-effective: Can be more cost-efficient than traditional methods like field surveys, especially for large areas.

(ii) Differentiate between IRS and INSAT series of satellites.

Ans: Here's a quick differentiation between IRS and INSAT:



(iii) Describe in brief the functioning of pushbroom scanner.

Ans: A pushbroom imager captures lines of data simultaneously like a broom sweeping. As the sensor platform moves, these lines stitch together like a photo finish, building a complete image. No moving mirrors, just rapid electronic scanning! 

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.

Ans: Whiskbroom Scanner:

Operation:

1. Scanning Mirror: A rotating mirror sweeps across the target area, directing reflected light onto a single detector.

2. Line-by-Line Build: As the mirror sweeps, the detector captures data one pixel at a time, building a line of the image.

3. Forward Movement: The platform (satellite, aircraft) moves forward, and the mirror starts scanning the next line.

4. Image Completion: By repeating steps 1-3 for all lines, the entire image is gradually built.

Diagram:

Imagine a broomstick with a tiny spotlight at one end, sweeping left and right. Each sweep captures a line, and multiple sweeps build the image.

Difference from Pushbroom:

*Moving Parts: Whiskbroom has a mechanical scanning mirror, while pushbroom relies entirely on electronic scanning.

*Data Acquisition: Whiskbroom scans one pixel at a time, while pushbroom captures entire lines simultaneously.

*Resolution and Speed: Pushbroom can achieve higher resolution due to longer integration time on each pixel, but scanning is slower than whiskbroom.

    Remember, whiskbroom is older technology, though still used in some applications. Pushbroom is generally preferred for its simplicity and higher resolution.

(ii) Identify and list the changes that can be observed in the vegetation of Himalayas (Fig.6.9).

Ans: Unfortunately, I don't have access to Figure 6.9 and need more information to identify the vegetation changes. To analyze the changes, I would need details like:

*Region or area depicted in the figure: Different Himalayan sections display diverse vegetation patterns and changes.

*Temporal scale: Comparing vegetation across different time periods helps identify trends and impacts.

*Specific features of the figure: What aspects of the vegetation are represented (e.g., forest cover, species composition, color variations)?

    With this information, I can analyze the figure and provide a comprehensive list of observable changes in the Himalayan vegetation.


Answer By: Himashree Bora.