TY - JOUR ID - datt1998 AU - Datt, Bisun TI - Remote Sensing of Chlorophyll a, Chlorophyll b, Chlorophyll a+b, and Total Carotenoid Content in Eucalyptus Leaves UR - http://www.sciencedirect.com/science/article/pii/S0034425798000467 DO - 10.1016/s0034-4257(98)00046-7 T2 - Remote Sensing of Environment PY - 1998 SN - 0034-4257 VL - 66 IS - 2 SP - 111-121 AB - Algorithms based on reflectance band ratios have been developed for the remote estimation of chlorophyll a, chlorophyll b, chlorophyll a+b, and total carotenoid content of Eucalyptus leaves. Reflectance spectra over the 400–2500 nm range with a spectral resolution of 2 nm and the content of chlorophylls a, b, a+b, and total carotenoids were determined for leaves from several Eucalyptus species covering a wide range of chlorophyll a content (0.0121–0.0435 mg/cm2). Maximum sensitivity of reflectance to variation in pigment content was found in the green wavelength region at 550 nm and at 708 nm in the far-red wavelengths. The reflectance in the main pigment absorption regions in the blue (400–500 nm) and red (660–690 nm) wavelengths proved to be insensitive to variation in pigment content. The ratio R672/(R550× R708) correlated best with chlorophyll a, chlorophyll a+b, and total carotenoid contents. The ratio R672/R550 correlated best with chlorophyll b content. Reflectance ratios involving near infrared bands such as R750/R550 and R750/R700 did not correlate well with pigment content. This was due to the differential scattering effects of the wide range of young and mature leaf samples. A method was developed for adjusting all spectra to the same level of scatter. The near-infrared-based reflectance ratios from the scatter adjusted spectra showed high sensitivity to pigment content. The ratio R860/(R550×R708) from the scatter adjusted spectra correlated best with chlorophyll a, chlorophyll a+b, and total carotenoid contents, while R860/R550 correlated best with chlorophyll b content. The newly developed algorithms were tested on a validation data set and allowed accurate estimates of leaf pigment content. The pigment contents estimated by the ratios from untransformed spectra, R672/(R550×R708) and R672/R550, were found to be not significantly different from the estimates obtained using the scatter-adjusted reflectance ratios, R860/(R550×R708) and R860/R550. ER - TY - JOUR ID - le_maire2004 AU - le Maire, G. AU - Francois, C. AU - Dufrene, E. TI - Towards universal broad leaf chlorophyll indices using PROSPECT simulated database and hyperspectral reflectance measurements DO - 10.1016/j.rse.2003.09.004 T2 - Remote Sensing of Environment PY - 2004 SN - 0034-4257 VL - 89 IS - 1 SP - 1-28 AB - Fifty-three leaves were randomly sampled on different deciduous tree species, representing a wide range of chlorophyll contents, tree ages, and leaf structural features. Their reflectance was measured between 400 and 800 nm with a 1-nm,step, and their chlorophyll content determined by extraction. A larger simulated database (11,583 spectra) was built using the PROSPECT model, in order to test, calibrate, and obtain universal indices, i.e., indices applicable to a wide range of species and leaf structure. To our knowledge, almost all leaf chlorophyll indices published in the literature since 1973 have been tested on both databases. Fourteen canonical types of indices (published ones and new ones) were identified, and their wavelengths calibrated on the simulated database as well as on the experimental database to determine the best wavelengths and, hence, the best performances in chlorophyll estimation for each index types. These indices go from simple reflectance ratios to more sophisticated indices Using reflectance first derivatives (using the Savitzky and Golay method). We also tested other nondestructive methods to obtain total chlorophyll concentration: SPAD (Minolta Camera, Osaka, Japan) and neural networks. The validity of the actual PROSPECT model is challenged by our results: Important discordances are found when the indices are calculated with PROSPECT compared to experimental data, especially for some indices and wavelengths. The discordance is even greater when the indices are determined with PROSPECT and applied on the experimental database. A new calibration of PROSPECT is therefore necessary for any study aiming at using simulated spectra to determine or to calibrate indices. The "peak jump" and the multiple-peak feature observed on the first derivative of the reflectances (e.g., in the Red-Edge Inflection Point [REIP] index) has been investigated. It was shown that chlorophyll absorption alone can explain this feature. The peak jump disqualifies' the REIP to be a valuable chlorophyll index. A simple modified difference ratio gave the best results among all published indices (cross-validated RMSE = 2.1 mug/cm(2) on the experimental database). After calibration on the experimental database, modified Simple Ratio (mSR) and modified Normalized Difference (mND) indices gave the best 2 performances (RMSECV = 1.8 mug/cm(2) on the experimental database). The new Double Difference (DD) index, although not the best on the 2), 2 experimental database (RMSECV 2.9 mug/cm(2)), has the best results on the larger simulated database (RMSE = 3.7 mug/cm(2)) and is expected to give good results on larger experimental databases. The best reflectance-based indices give better performances than the current commercial nondestructive device SPAD (RMSECV = 4.5 mug/cm(2)). In This leaf-level study, the best indices are very near from each other, so that complex methods are useless: REIP-like, neural networks, and derivative-based indices are not necessary and give worst results than simpler properly chosen indices. These conclusions will certainly be different for. a canopy-level study, where the derivative-based indices may perform significantly better than the other ones. (C) 2003 Elsevier Inc. All rights reserved. KW - universal broad leaf chlorophyll indices. PROSPECT. hyperspectral. reflectance measurements. neural-network classification. radiative-transfer models. remote-sensing. data. red-edge. vegetation indexes. spectral reflectance. optical-properties. bidirectio ER - TY - JOUR ID - main2011 AU - Main, Russell AU - Cho, Moses Azong AU - Mathieu, Renaud AU - O’Kennedy, Martha M. AU - Ramoelo, Abel AU - Koch, Susan TI - An investigation into robust spectral indices for leaf chlorophyll estimation UR - http://www.sciencedirect.com/science/article/pii/S092427161100089X DO - 10.1016/j.isprsjprs.2011.08.001 T2 - ISPRS Journal of Photogrammetry and Remote Sensing PY - 2011 SN - 0924-2716 VL - 66 IS - 6 SP - 751-761 AB - Quantifying photosynthetic activity at the regional scale can provide important information to resource managers, planners and global ecosystem modelling efforts. With increasing availability of both hyperspectral and narrow band multispectral remote sensing data, new users are faced with a plethora of options when choosing an optical index to relate to their chosen or canopy parameter. The literature base regarding optical indices (particularly chlorophyll indices) is wide ranging and extensive, however it is without much consensus regarding robust indices. The wider spectral community could benefit from studies that apply a variety of published indices to differing sets of species data. The consistency and robustness of 73 published chlorophyll spectral indices have been assessed, using leaf level hyperspectral data collected from three crop species and a variety of savanna tree species. Linear regression between total leaf chlorophyll content and bootstrapping were used to determine the leafpredictive capabilities of the various indices. The indices were then ranked based on the prediction error (the average root mean square error (RMSE)) derived from the bootstrapping process involving 1000 iterative resampling with replacement. The results show two red-edge derivative based indices (red-edge position via linear extrapolation index and the modified red-edge inflection point index) as the most consistent and robust, and that the majority of the top performing indices (in spite of species variability) were simple ratio or normalised difference indices that are based on off-chlorophyll absorption centre wavebands (690–730 nm). KW - Leaf level reflectance KW - Leaf chlorophyll KW - Red-edge KW - Vegetation indices KW - Photosynthetic activity ER - TY - ELEC ID - idb AU - Henrich, V. AU - Krauss, G. AU - Götze, C. AU - Sandow, C. TI - The IndexDatabase UR - https://www.indexdatabase.de/ CY - Bonn PY - 2011 DA - 2011 ER -