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Proceedings Paper

GAPF (Geometrical and physical filter): a temporal filtering method for NOAA/HRPT data
Author(s): Olivier Amram; S. Cherchali; Guy Flouzat
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Paper Abstract

In order to reduce the problems of clouds, atmospheric variations, view angle effects, and the soil background variations in the high temporal frequency AVHRR data, a compositing technique is usually employed. Current compositing techniques use a single pixel selection criterion of outputing the input pixel of maximum value NDVI. Problems, however, exist due to the use and to the imperfection of the pixel selection criteria of the algorithm itself. The NDVI was found to have the maximum value under an ideal observation condition, while the single pixel selection criterion favors the large off-nadir sensor view angles. Consequently, the composited data still consist of substantial noise. To further reduce the noise, a new set of pixel selection filtering was proposed for compositing NDVI data. It consists of taking into account the biological characteristics and eliminating the temporal variations of the signal which are false. For this we used a mixed method of physical threshold and geometrical operations (GAPF: geometrical and physical filter). The association of the two criterion leads to a mixed `physical and biological' method. The alternative approach showed that the high frequency noises were greatly reduced, while more valuable data were retained.

Paper Details

Date Published: 31 January 1995
PDF: 12 pages
Proc. SPIE 2314, Multispectral and Microwave Sensing of Forestry, Hydrology, and Natural Resources, (31 January 1995); doi: 10.1117/12.200776
Show Author Affiliations
Olivier Amram, Ctr. d'Etude Spatiale des Rayonnements (France)
S. Cherchali, Ctr. d'Etude Spatiale des Rayonnements (France)
Guy Flouzat, Ctr. d'Etude Spatiale des Rayonnements (France)

Published in SPIE Proceedings Vol. 2314:
Multispectral and Microwave Sensing of Forestry, Hydrology, and Natural Resources
Eric Mougin; K. Jon Ranson; James Alan Smith, Editor(s)

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