Technical Note: On masking land pixels in empirical orthogonal function analysis of sequences of sea surface images

• Published in: International journal of remote sensing Vol. 25; no. 18; pp. 3675 - 3685
• Main Authors: Borzelli, G., Ciappa, A., Ligi, R., Pietranera, L.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 01.09.2004
• ISSN: 0143-1161; 1366-5901
• DOI: 10.1080/01431160310001653537

Implications of masking land pixels in series of images of the sea surface are investigated. The study is carried out by means of analytical and numerical arguments. An algorithm that performs empirical orthogonal function (EOF) analysis by selecting from original images only the subset of unmasked pixels, has been set up and used on an exemplar dataset constituted by 206 images of the sea level anomaly (SLA) provided by the Topex/Poseidon mission over the Mediterranean Sea. It is shown that, as far as singular value decomposition (SVD) and spatial EOF analyses are involved, different masking values of land pixels modify the relative importance of empirical functions (EOFs) and the corresponding temporal coefficient, while results obtained with temporal EOF analysis remain unchanged.