Preliminary validation of MERIS water products for Belgian coastal waters
Ruddick, K.G.; De Cauwer, V.; Park, Y.; Becu, G.; De Blauwe, J.-P.; De Vreker, E.; Deschamps, P.-Y.; Knockaert, M.; Nechad, B.; Pollentier, A.; Roose, P.; Saudemont, D.; Van Tuyckom, D. (2002). Preliminary validation of MERIS water products for Belgian coastal waters, in: Envisat Validation Workshop 9-13 December 2002 ESRIN, Frascati, Italy. ESA Special Publications, 531: pp. 1-15
In: (2002). Envisat Validation Workshop 9-13 December 2002 ESRIN, Frascati, Italy. ESA Special Publications, 531. ESA Publications Office[s.l.], meer
In: ESA Special Publications. ESA Publications Office. ISSN 0379-6566; e-ISSN 1609-0438, meer
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| Beschikbaar in | Auteurs |
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Documenttype: Congresbijdrage
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| Project | Top | Auteurs |
- BELCOLOUR - Optical remote sensing of coastal waters, meer
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| Auteurs | | Top |
- Ruddick, K.G., meer
- De Cauwer, V., meer
- Park, Y., meer
- Becu, G.
- De Blauwe, J.-P., meer
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- De Vreker, E.
- Deschamps, P.-Y.
- Knockaert, M., meer
- Nechad, B., meer
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| Abstract |
This paper describes the methods used to acquire sea-level data for validation of MERIS water products in Belgian coastal waters and comparison of such measurements with MERIS level 2 data as available in November 2002. Results are presented for two Reduced Resolution level 2 images for which sea-level match-up data exists. One image was acquired during partially cloudy skies - while not appropriate for quantitative validation of the water products themselves, this image is useful for validation of the various quality and confidence flags supplied with the MERIS products. The second image was acquired during clear sky conditions and is optimal for quantitative validation of water-leaving reflectance, algal pigment index (chlorophyll concentration) and total suspended matter concentration. Firstly, a qualitative assessment is made of the images based on knowledge of the region and of inconsistencies between the products themselves. This assessment suggests that many pixels which are partially or wholly cloudy are not identified as such, giving an unreliable impression of product quality to users. Furthermore, unrealistic spatial discontinuities are observed in products because of switching of the case 2S flag. It is recommended that more attention be paid to validation of the MERIS L2 flags and especially cloud pixel identification and the impact of spatial variability of the case 2S flag. Secondly a quantitative assessment is made of products using the sea-level match-up data. For the image with clear sky conditions water-leaving reflectance in the blue is severely overestimated by MERIS because of underestimation of aerosol optical thickness and epsilon factor. It is recommended that the performance of the turbid water atmospheric correction be investigated in more detail and with more imagery for this and other regions. |
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