Unsupervised classification attempts to find clusters in n-dimensional space based on the reflectance values, and assigns to those clusters to a group. Hopefully there will be a reason for the cluster, which will correspond to a particular category, but that can only be interpreted by the user. The selected colors are random. On one scene the water might be blue, and on the next it will be vegetation.
|Cluster for 6 band Landsat TM image of Hanging Rock quadrangle.||Legend. This will be in a .VAT.DBF file, which you can edit with descriptive names for clusters and change color assignments.|
Clustering will be based on a limited subsample of points. They will be selected from the current screen, so you should subset the satellite map to cover just the area of interest. The entire image can be classified, but the results will be most valid in the map region.
Manual, equivalent options
You can also use the Orfeo toobox for unsupervised classification.
Clustering Delphi code from Fred Edberg; 11/30/02 (email@example.com) and uses K mean clustering.
Last revision 7/1/2020