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Multiple cost functions and regularization options for improved retrieval of leaf chlorophyll content and LAI through inversion of the PROSAIL model

Rivera, Juan Pablo, Verrelst, Jochem, Leonenko, Ganna M. and Moreno, José 2013. Multiple cost functions and regularization options for improved retrieval of leaf chlorophyll content and LAI through inversion of the PROSAIL model. Remote Sensing 5 (7) , pp. 3280-3304. 10.3390/rs5073280

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Abstract

Lookup-table (LUT)-based radiative transfer model inversion is considered a physically-sound and robust method to retrieve biophysical parameters from Earth observation data but regularization strategies are needed to mitigate the drawback of ill-posedness. We systematically evaluated various regularization options to improve leaf chlorophyll content (LCC) and leaf area index (LAI) retrievals over agricultural lands, including the role of (1) cost functions (CFs); (2) added noise; and (3) multiple solutions in LUT-based inversion. Three families of CFs were compared: information measures, M-estimates and minimum contrast methods. We have only selected CFs without additional parameters to be tuned, and thus they can be immediately implemented in processing chains. The coupled leaf/canopy model PROSAIL was inverted against simulated Sentinel-2 imagery at 20 m spatial resolution (8 bands) and validated against field data from the ESA-led SPARC (Barrax, Spain) campaign. For all 18 considered CFs with noise introduction and opting for the mean of multiple best solutions considerably improved retrievals; relative errors can be twice reduced as opposed to those without these regularization options. M-estimates were found most successful, but also data normalization influences the accuracy of the retrievals. Here, best LCC retrievals were obtained using a normalized “L1 -estimate” function with a relative error of 17.6% (r2 : 0.73), while best LAI retrievals were obtained through non-normalized “least-squares estimator” (LSE) with a relative error of 15.3% (r2 : 0.74).

Item Type: Article
Date Type: Publication
Status: Published
Schools: Mathematics
Medicine
MRC Centre for Neuropsychiatric Genetics and Genomics (CNGG)
Subjects: Q Science > QA Mathematics
Uncontrolled Keywords: Biophysical parameters; LUT-based inversion; cost functions; radiative transfer models; PROSAIL; Sentinel-2.
Publisher: MDPI
ISSN: 2072-4292
Date of First Compliant Deposit: 18 April 2017
Date of Acceptance: 26 June 2013
Last Modified: 05 Jun 2017 04:39
URI: http://orca-mwe.cf.ac.uk/id/eprint/64172

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