Microwave remote sensing

Question 1

What is microwave remote sensing?

Answer 1

It is the use of electromagnetic waves with wavelengths between 1 cm and 1 m for imaging.

Question 2

Why are longer wavelengths in microwave sensing advantageous?

Answer 2

They can penetrate clouds and are independent of atmospheric conditions like haze.

Question 3

Which part of the electromagnetic spectrum does microwave remote sensing use?

Answer 3

Microwave region, with wavelengths from 1 cm to 1 m.

Question 4

What is the key concept behind microwave remote sensing?

Answer 4

Imaging using the microwave portion of the electromagnetic spectrum.

Question 5

What is imaging in the context of microwave remote sensing?

Answer 5

Creating images using reflected or emitted microwave signals.

Question 6

What are geometric properties in remote sensing?

Answer 6

They refer to spatial characteristics and accuracy of the images.

Question 7

Name a distortion commonly found in microwave images.

Answer 7

Foreshortening.

Question 8

What is foreshortening in radar images?

Answer 8

Compression of image features due to steep terrain slopes toward the sensor.

Question 9

What is layover in radar imagery?

Answer 9

When the top of a tall object is imaged before the base, causing a displacement.

Question 10

What is shadowing in radar imagery?

Answer 10

Areas that are not imaged due to lack of radar illumination.

Question 11

What causes geometric distortions in radar images?

Answer 11

Terrain variation and side-looking radar geometry.

Question 12

How can distortions in microwave images be addressed?

Answer 12

Using geometric correction techniques and accurate terrain models.

Question 13

What is SAR?

Answer 13

Synthetic Aperture Radar, used for high-resolution microwave imaging.

Question 14

What is polarization in radar systems?

Answer 14

Orientation of the electric field of the transmitted or received signal.

Question 15

What does HH polarization mean?

Answer 15

Horizontally transmitted and horizontally received radar signals.

Question 16

What is multi-look processing in SAR?

Answer 16

Averaging multiple looks to reduce speckle noise.

Question 17

What is speckle in radar images?

Answer 17

Granular noise inherent in coherent imaging systems.

Question 18

How is speckle reduced?

Answer 18

By multi-looking or filtering techniques.

Question 19

What is an advantage of radar over optical sensors?

Answer 19

Ability to operate in all weather and lighting conditions.

Question 20

What type of sensor is radar?

Answer 20

An active sensor that emits its own energy.

Question 21

What is the difference between active and passive sensors?

Answer 21

Active sensors emit energy; passive sensors detect natural energy.

Question 22

What are backscatter coefficients?

Answer 22

Quantitative measure of radar signal reflected back to the sensor.

Question 23

What influences radar backscatter?

Answer 23

Surface roughness, moisture content, and incidence angle.

Question 24

What is incidence angle?

Answer 24

The angle between the radar beam and the normal to the surface.

Question 25

Why is calibration important in radar systems?

Answer 25

To ensure accuracy and consistency of the data.

Question 26

What is image interpretation in microwave sensing?

Answer 26

Analyzing images to identify features and patterns.

Question 27

What tools assist in interpreting microwave images?

Answer 27

Histograms, filters, and edge detection algorithms.

Question 28

What is meant by advanced image processing?

Answer 28

Use of algorithms and software to enhance, classify, or analyze images.

Question 29

Name one advanced technique for image processing.

Answer 29

Classification using machine learning.

Question 30

What is geocoding in remote sensing?

Answer 30

Aligning image data to geographic coordinates.

Question 31

What is the significance of radiometric calibration?

Answer 31

It ensures the brightness values are physically meaningful.

Question 32

How does terrain affect radar images?

Answer 32

It can cause distortion such as layover or shadowing.

Question 33

What is remote sensing?

Answer 33

The process of detecting and monitoring physical characteristics of an area from a distance.

Question 34

What are applications of microwave remote sensing?

Answer 34

Agriculture, forestry, hydrology, geology, and disaster monitoring.

Question 35

How does moisture affect radar backscatter?

Answer 35

Increases the backscatter due to higher dielectric constant.

Question 36

Why is radar useful in agriculture?

Answer 36

It can monitor soil moisture and crop conditions regardless of weather.

Question 37

What is slant-range geometry?

Answer 37

The actual line-of-sight distance between the radar and ground target.

Question 38

What is ground-range geometry?

Answer 38

The horizontal distance between radar projection and ground target.

Question 39

How can image distortions be corrected?

Answer 39

Using ground control points and digital elevation models.

Question 40

What is the use of digital elevation models in radar?

Answer 40

To correct geometric distortions and derive terrain information.

Question 41

What role do sensors play in remote sensing?

Answer 41

They collect data by detecting electromagnetic radiation.

Question 42

What are radargrammetric techniques?

Answer 42

Methods that derive elevation from stereo radar images.

Question 43

What is interferometry in radar?

Answer 43

Using phase differences between two images to map elevation or motion.

Question 44

What is coherence in radar interferometry?

Answer 44

A measure of similarity between radar signals for interferometry.

Question 45

What is temporal decorrelation?

Answer 45

Loss of coherence due to changes in the surface between radar acquisitions.

Question 46

What is a radar image pixel value called?

Answer 46

Digital Number (DN) or backscatter intensity.

Question 47

What is side-looking geometry in radar?

Answer 47

Radar that views the terrain from the side, not directly overhead.

Question 48

What is range resolution in radar?

Answer 48

The ability to distinguish between two objects in the direction of range.