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- Title
Multiple Cost Functions and Regularization Options for Improved Retrieval of Leaf Chlorophyll Content and LAI through Inversion of the PROSAIL Model.
- Authors
Rivera, Juan Pablo; Verrelst, Jochem; Leonenko, Ganna; Moreno, José
- 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).
- Subjects
RADIATIVE transfer; LEAF area index; FARMS; LEAST squares; CHLOROPHYLL; RADIATION absorption; RADIATIVE transfer equation
- Publication
Remote Sensing, 2013, Vol 5, Issue 7, p3280
- ISSN
2072-4292
- Publication type
Article
- DOI
10.3390/rs5073280