Remote Sensing: Enhancements Flashcards
How may a radar image be incorporated with an optical image by using the HIS colour space transform?
Synthetic Color Image transform
Pseudo-colour transform
Which is the wavelength range for visible light?
consists of wavelengths ranging from approximately 780 nanometer (7.80 x 10-7 m) down to 390 nanometer (3.90 x 10-7 m).
Which is the main purpose of digital filters
: (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.
The histogram of a low contrast image will have which dominant feature?
a narrow bell curve in the centre of the Digital number vs frequency graph.
Which filters are low-pass filter?
Emphasize Low Frequency, large-scale features
Remove High-Frequency features (like noise).
- Mean Filter
- Median filter
- Olympic filter
- Majority filter
Which filters are high-pass filter?
Kernal: kI + (1-k)A Kernal = I – kL Edge Enhancement Roberts Filter Sobel Edge Detection
When performing an image enhancement using a Fast Fourier Transform, which portions of the frequency (star) diagram are masked out, to emphasise spatial contrast?
Apply a mask to the frequency domain image by selecting frequencies above or below a threshold
Why can Principle Components Analysis help to reduce image dimensions?
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.
Why would you apply a grey-level threshold?
For Contrast Manipulation
What can be achieved with image multiplication?
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.
Why would you apply a grey-level threshold?
For Contrast Manipulation, To enhance spatial contrast in an image
In the HIS colour model, which parameter represents the wavelength of light recorded?
Hue
Why do most (optical) satellite images require contrast stretching?
to increase the dynamic range of gray levels in the image being processed
Why do most (optical) satellite images require contrast stretching?
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
Which of the following are not an output of the forward Fourier transform?
Phase