NOISE FILTER AND PC FILTERING
UFO GROUP
LUISA MARIA GRAZIA SILVIA VITO
OUTLINEOUTLINE
Presence of noise.Presence of noise.
FFT filter.FFT filter.
PCA filter.PCA filter.
Conclusions.Conclusions.
PRESENCE OF NOISEPRESENCE OF NOISE
Noise affecting data is due to several Noise affecting data is due to several factors.factors.– Correlated noise (calibration, instrumental Correlated noise (calibration, instrumental
vibration)vibration)– Detectors noise:Detectors noise:
randomrandomgaussiangaussiantime and space decorrelationtime and space decorrelation
FFT FILTER ON AIRS DATAFFT FILTER ON AIRS DATA
Selection of two neighbor wavelengths with Selection of two neighbor wavelengths with
close Radiances.close Radiances. Difference of the selected wavelengths for Difference of the selected wavelengths for
the same image.the same image. FFT: noise corresponds to higher FFT: noise corresponds to higher
frequencies.frequencies.
FFT
R(1)-R(2)
It displays popping noise
Frequencies
FFT FILTER RESULTSFFT FILTER RESULTSThis filter doesn’t work!!
PCA – Principal Component PCA – Principal Component AnalysisAnalysis
It allows to reduce the It allows to reduce the dimensionality of the problem.dimensionality of the problem.
It finds the Principal It finds the Principal components (the eigenvectors components (the eigenvectors of the observation covariance of the observation covariance matrix).matrix).
Most of atmospheric of the Most of atmospheric of the observed variance is in the first observed variance is in the first PCs. PCs.
Right number of PCs allows for Right number of PCs allows for noise reduction and information noise reduction and information preservation.preservation.
UNFILTERED DATA101 AIRS SPECTRA
STANDARD NOISESTANDARD NOISE
RANGE CONSIDERED: 700-1100 cm-1
FILTER SENSITIVITY TO THE FILTER SENSITIVITY TO THE NUMBER OF PCsNUMBER OF PCs
# PCs =10 # PCs =175
X 5
MEAN OF NORMALIZED DIFFERENCEBETWEEN ESTIMATED AND STANDARD NOISE
RESULTS - # PCs = 10 RESULTS - # PCs = 10
Gaussian noise
RESULTS - # PCs = 175 RESULTS - # PCs = 175
Gaussian noise
FILTERED SPECTRAFILTERED SPECTRA
UNFILTERED SPECTRA
# PCs = 175 # PCs = 10
……that’s all folks!!that’s all folks!!
THANKS FOR YOUR THANKS FOR YOUR ATTENTION!!ATTENTION!!