Prototyping Sentinel-2 green LAI and brown LAI products for cropland monitoring

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F86652079%3A_____%2F21%3A00562849" target="_blank" >RIV/86652079:_____/21:00562849 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S0034425720305411?via%3Dihub" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0034425720305411?via%3Dihub</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.rse.2020.112168" target="_blank" >10.1016/j.rse.2020.112168</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Prototyping Sentinel-2 green LAI and brown LAI products for cropland monitoring

Popis výsledku v původním jazyce

For agricultural applications, identification of non-photosynthetic above-ground vegetation is of great interest as it contributes to assess harvest practices, detecting crop residues or drought events, as well as to better predict the carbon, water and nutrients uptake. While the mapping of green Leaf Area Index (LAI) is well established, current operational retrieval models are not calibrated for LAI estimation over senescent, brown vegetation. This not only leads to an underestimation of LAI when crops are ripening, but is also a missed monitoring opportunity. The high spatial and temporal resolution of Sentinel-2 (52) satellites constellation offers the possibility to estimate brown LAI (LAI(B)) next to green LAI (LAI(G)). By using LAI ground measurements from multiple campaigns associated with airborne or satellite spectra, Gaussian processes regression (GPR) models were developed for both LAI(G) and LAI(B), providing alongside associated uncertainty estimates, which allows to mask out unreliable LAI retrievals with higher uncertainties. A processing chain was implemented to apply both models to 52 images, generating a multiband LAI product at 20 m spatial resolution. The models were adequately validated with insitu data from various European study sites (LAI(G): R-2 = 0.7, RMSE = 0.67 m(2)/m(2), LAI(B): R-2 = 0.62, RMSE = 0.43 m(2)/m(2)). Thanks to the 52 bands in the red edge (B5: 705 nm and B6: 740 nm) and in the shortwave infrared (B12: 2190 nm) a distinction between LAI(G) and LAI(B) can be achieved. To demonstrate the capability of LAI(B) to identify when crops start senescing, 52 time series were processed over multiple European study sites and seasonal maps were produced, which show the onset of crop senescence after the green vegetation peak. Particularly, the LAI(B) product permits the detection of harvest (i.e., sudden drop in LAI(B)) and the determination of crop residues (i.e., remaining LAI(B)), although a better spectral sampling in the shortwave infrared would have been desirable to disentangle brown LAI from soil variability and its perturbing effects. Finally, a single total LAI product was created by merging LAI(G) and LAI(B) estimates, and then compared to the LAI derived from 52 L2B biophysical processor integrated in SNAP. The spatiotemporal analysis results confirmed the improvement of the proposed descriptors with respect to the standard SNAP LAI product accounting only for photosynthetically active green vegetation.

Název v anglickém jazyce

Prototyping Sentinel-2 green LAI and brown LAI products for cropland monitoring

Popis výsledku anglicky

For agricultural applications, identification of non-photosynthetic above-ground vegetation is of great interest as it contributes to assess harvest practices, detecting crop residues or drought events, as well as to better predict the carbon, water and nutrients uptake. While the mapping of green Leaf Area Index (LAI) is well established, current operational retrieval models are not calibrated for LAI estimation over senescent, brown vegetation. This not only leads to an underestimation of LAI when crops are ripening, but is also a missed monitoring opportunity. The high spatial and temporal resolution of Sentinel-2 (52) satellites constellation offers the possibility to estimate brown LAI (LAI(B)) next to green LAI (LAI(G)). By using LAI ground measurements from multiple campaigns associated with airborne or satellite spectra, Gaussian processes regression (GPR) models were developed for both LAI(G) and LAI(B), providing alongside associated uncertainty estimates, which allows to mask out unreliable LAI retrievals with higher uncertainties. A processing chain was implemented to apply both models to 52 images, generating a multiband LAI product at 20 m spatial resolution. The models were adequately validated with insitu data from various European study sites (LAI(G): R-2 = 0.7, RMSE = 0.67 m(2)/m(2), LAI(B): R-2 = 0.62, RMSE = 0.43 m(2)/m(2)). Thanks to the 52 bands in the red edge (B5: 705 nm and B6: 740 nm) and in the shortwave infrared (B12: 2190 nm) a distinction between LAI(G) and LAI(B) can be achieved. To demonstrate the capability of LAI(B) to identify when crops start senescing, 52 time series were processed over multiple European study sites and seasonal maps were produced, which show the onset of crop senescence after the green vegetation peak. Particularly, the LAI(B) product permits the detection of harvest (i.e., sudden drop in LAI(B)) and the determination of crop residues (i.e., remaining LAI(B)), although a better spectral sampling in the shortwave infrared would have been desirable to disentangle brown LAI from soil variability and its perturbing effects. Finally, a single total LAI product was created by merging LAI(G) and LAI(B) estimates, and then compared to the LAI derived from 52 L2B biophysical processor integrated in SNAP. The spatiotemporal analysis results confirmed the improvement of the proposed descriptors with respect to the standard SNAP LAI product accounting only for photosynthetically active green vegetation.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10618 - Ecology

Projekt

—

Návaznosti

—

Rok uplatnění

2021

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Remote Sensing of Environment

ISSN

0034-4257

e-ISSN

1879-0704

Svazek periodika

255

Číslo periodika v rámci svazku

MAR 15

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

16

Strana od-do

112168

Kód UT WoS článku

000619232500004

EID výsledku v databázi Scopus

2-s2.0-85096520859