Image classification- unsupervised Flashcards
What is image classification?
A procedure that uses the remotely sensed image data to produce maps showing location and extent of carious selected land cover types
How does unsupervised classification work?
Take groups of pixels that have similar values
They are more likely to be similar land cover types
Convert data to information
Even though different land cover types could still have similar spectral characteristics
What is a feature space plot?
A scatter plot between different wavebands (x and y), brighter colours include higher frequency
How to produce the classification map?
The pixels have been assigned to a class based on the spectral statistics of the image
The user now needs to determine what land cover type each class in the image refers to e.g. black pixels are roads, green is trees
What is unsupervised classification?
A classification method that does not compare the pixels to any prior information. Instead, it divides data points into classes based on the properties of the data
What are the advantages of unsupervised classification?
No extensive prior knowledge of the area required
Opportunities of human error are minimised
Unique classes can be identified e.g different tree species
What are the disadvantages of unsupervised classification?
Spectral classes vs information classes
Limited control over classes
Comparison between two or more unsupervised classifications is difficult
