Remote sensing topic: If two objects with very similar spectral signatures are m
ID: 116132 • Letter: R
Question
Remote sensing topic:
If two objects with very similar spectral signatures are measured at different viewing geometries will the spectral angle increase, decrease, or stay the same, as opposed to viewing them at the same geometry? Why?
Note:
SAM(SPECTRAL ANGLE MAPPER ) determines the similarity of an unknown spectrum t to a reference spectrum r , where nb equals the number of bands in the image.
smaller angle: closer match between the spectrum and the reference spectrum (in the figure: material A and material B)
-The technique is relatively insensitive to illumination effects.
-Poorly illuminated pixels will fall closer to the origin.
-1 1/2 17Explanation / Answer
As the formula of smaller angle if we increase t or r then the angle will also increase siminteneously .spectral angle is measured between material A and B.In question written that we have same spectral signature and the same geometry so the angle will change (smaller angle) but the spectral angle will be same as it will be effected by the simuntenous decrease of r when t is being increased .