Remote Sensing: Enhancements Flashcards

1
Q

How may a radar image be incorporated with an optical image by using the HIS colour space transform?

A

Synthetic Color Image transform

Pseudo-colour transform

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2
Q

Which is the wavelength range for visible light?

A

consists of wavelengths ranging from approximately 780 nanometer (7.80 x 10-7 m) down to 390 nanometer (3.90 x 10-7 m).

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3
Q

Which is the main purpose of digital filters

A

: (1) separation of signals that have been combined, and (2) restoration of signals that have been distorted in some way. Analog (electronic) filters can be used for these same tasks; however, digital filters can achieve far superior results.

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4
Q

The histogram of a low contrast image will have which dominant feature?

A

a narrow bell curve in the centre of the Digital number vs frequency graph.

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5
Q

Which filters are low-pass filter?

A

Emphasize Low Frequency, large-scale features
Remove High-Frequency features (like noise).
- Mean Filter
- Median filter
- Olympic filter
- Majority filter

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6
Q

Which filters are high-pass filter?

A
Kernal: kI + (1-k)A
Kernal = I – kL
Edge Enhancement
Roberts Filter
Sobel Edge Detection
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7
Q

When performing an image enhancement using a Fast Fourier Transform, which portions of the frequency (star) diagram are masked out, to emphasise spatial contrast?

A

Apply a mask to the frequency domain image by selecting frequencies above or below a threshold

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8
Q

Why can Principle Components Analysis help to reduce image dimensions?

A

So to sum up, the idea of PCA is simple — reduce the number of variables of a data set, while preserving as much information as possible.

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9
Q

Why would you apply a grey-level threshold?

A

For Contrast Manipulation

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10
Q

What can be achieved with image multiplication?

A

Multiplication is performed on 2 images
Use
if the image is composed of 2 or more distinctive regions
and analyst is only interested in one of these regions.

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11
Q

Why would you apply a grey-level threshold?

A

For Contrast Manipulation, To enhance spatial contrast in an image

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12
Q

In the HIS colour model, which parameter represents the wavelength of light recorded?

A

Hue

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13
Q

Why do most (optical) satellite images require contrast stretching?

A

to increase the dynamic range of gray levels in the image being processed

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14
Q

Why do most (optical) satellite images require contrast stretching?

A

to increase the dynamic range of gray levels in the image being processed

Sensors are designed to operate in a wide range of land cover and lighting conditions

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15
Q

Which of the following are not an output of the forward Fourier transform?

A

Phase

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