Section 6 Flashcards
What are the three types of data manipulation for digital analysis
Multispectral band ratioing
Linear data transformation
Band-moment transformations
What are the four classes of image quality?
Low radiance/albedo
High radiance/albedo
Low contrast
High contrast
What is contrast stretching?
It expands the original brightness values in an image to increase contrast of the image. This can be done linear or non linear
What is a linear stretch?
It increases the contrast while preserving the original radiance relationships of the pixels
What is a non linear stretch?
A stretch similar to the linear stretch in that the original radiance relationships were not maintained
What is an example of a nonlinear enhancement?
Histogram equalization
Define spatial filtering.
The extraction of information contained in the spatial domain instead of the spectral. This is done in a kernel of pixels
Name the two types of spatial filtering
Convolution (low pass) Non convolution (high pass)
What is a convolution filter?
A low pass spatial filter. This smooths an image, blurring it slightly.
What is a non convolution filter?
A spatial high pass filter. It enhances abrupt changes
What is low frequency distribution?
When the brightness changes very little or it is gradual change
What is high frequency distribution?
Values that change very dramatically
What is a Fast Fourier Transform?
It can be a high or low pass filter that breaks an image down into frequency and direction. It removes repetitive noise.
What are two types of FFT?
Pass procedure: creates a mask and only inside the mask is kept
Cut procedure: creates a mask and only outside the mask is kept
What does an edge detection filter do?
Enhance linear features in an image. A high pass filter is an example of this
What are the two types of edge detection filters?
Non directional: deal with linear features in all directions.
Directional: accentuate feature in one direction
What is a LaPlacian filter?
A non directional filter that is an edge detection filter. It emphasizes the maximum values in the image
What is a compass gradient filter?
A directional edge detection filter. It enhances features according to compass directions
What is a filter similar to a compass gradient filter, but is a non linear filter?
Sobel filter
What is the purpose of using a band ratio?
The enhance differences in brightness between surfaces
What is principal component analysis?
It reduces the amount of bands but keeps information. It decorrelates data while maintaining statistical value. Correlates spectral bands
What is the tasselled cap transformation?
It creates a soil, green and wetness index
What is a band moment analysis?
A transformation to get statistical data, it looks through the spectral data of a pixel and creates a cube.
What are three types of data enhancement for image production?
Contrast stretch
Spatial filtering
Edge enhancement
