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Evaluation of MERIS FR LAI products derived using MERIS TOA_VEG and TOC_VEG algorithms over four different land uses in Canada

Francis Canisius(1) and Richard Fernandes(1)

(1) Canada Center for Remote Sensing (CCRS), 588 Booth street, Ottawa, Ontario K1A 0Y7, Canada

Abstract

In this study, LAI was computed with MERIS TOA_VEG and TOC_VEG algorithms that were developed to derive LAI from MERIS data. The evaluation of the estimation is performed by comparing the estimated LAI from MERIS data to those estimated using other LAI algorithms that are commonly used in Canada, available regional LAI products and LAI measured from field. The field site is mainly an agricultural area, devoted to corn, bean, pasture and wheat cultivation, located in the Nepean area, close to the capital city of Canada. Ground LAI of each large agriculture field and number of forest patches were measured using DHP method during the 2006 growing season (4/5th of July). The MERIS data that was used to estimate LAI was acquired on 3rd July 2006, just a day difference from the day of field campaign. It was found that LAI was slightly overestimated in both TOA_VEG and TOC_VEG algorithms in low LAI range and underestimated in higher range of LAI. Further, the estimated LAI using these two algorithms may not always lead to a more accurate estimation of true LAI and that it may be possible to estimate effective LAI or LAI during the early stages of crop growth. Comparatively TOA_VEG shows little higher correlation with field LAI measurements than TOC_VEG and the coefficient of determination (R2) between TOA_VEG algorithm estimation and measured effective LAI is 0.63 and RMSE is 0.87.

Key words: MERIS, LAI, validation

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry