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!!