Using Sentinel-2 data for retrieving crop properties: the potato case

Workshop Agriculture and Earth Observation 4-5 July 2017, Jan Clevers

Contents

Introduction Material and methods

● Vegetation indices ● Test site & field radiometry ● Sentinel-2

Results ● LAI, LCC and CCC estimation ● Spatial patterns

Conclusions

Introduction

Important properties for crop monitoring (e.g., within the field of precision agriculture) ● Leaf area index: LAI ● Leaf chlorophyll content: LCC ● Canopy chlorophyll content: CCC

Question: Can we use Sentinel-2 derived vegetation indices for estimating these properties? “proof of concept”

Material and methods

Quantitative remote sensing

Physical methods Statistical methods

Vegetation indices Radiative transfer models

Hybrid method

Vegetation indices (VI)

LAI estimation ● WDVI (weighted difference VI) Clevers, 1989

LCC estimation ● TCARI/OSAVI Haboudane et al. 2002

● CVI [(R842/R560)/(R560/R665)] Vincini et al. 2008

CCC estimation ● CIred-edge = R783/R705 -1 Gitelson et al. 2003

● CIgreen = R842/R560 -1 Gitelson et al. 2003

● REIP (linear interpolation) Guyot & Baret 1988

Test site: potato crop experiment in 2016

Field radiometry (Cropscan)

Reference for crop property determination Validated with LAI-2000 and SPAD measurements

using potato experiments 2010-2014:

𝐿𝐿𝐿𝐿𝐿𝐿 = 0.109 × 𝑊𝑊𝑊𝑊𝑊𝑊𝐿𝐿 − 0.3233

𝐿𝐿𝐿𝐿𝐿𝐿 = −3.5884 × 𝑇𝑇𝐿𝐿𝐿𝐿𝑇𝑇𝐿𝐿/𝑂𝑂𝑂𝑂𝐿𝐿𝑊𝑊𝐿𝐿 + 1.0369

𝐿𝐿𝐿𝐿𝐿𝐿 = 0.8013 × 𝐿𝐿𝐿𝐿𝑟𝑟𝑟𝑟𝑟𝑟−𝑟𝑟𝑟𝑟𝑒𝑒𝑟𝑟 − 0.4704

Sentinel-2

Use of TOC reflectances for calculating crop properties Using SNAP and Sen2Cor toolboxes Four dates in relevant part of season (June – mid August)

LAI estimation: WDVI

LAI estimation: WDVI

LOO cross-validation:

RMSEP = 0.36

LCC estimation: TCARI/OSAVI

LCC estimation: TCARI/OSAVI

LOO cross-validation:

RMSEP = 0.062 g.m-2

LCC estimation: CVI

LCC estimation: CVI

LOO cross-validation:

RMSEP = 0.066 g.m-2

CCC estimation: CIred-edge

CCC estimation: CIred-edge

LOO cross-validation:

RMSEP = 0.43 g.m-2

CCC estimation: CIgreen

CCC estimation: CIgreen

LOO cross-validation:

RMSEP = 0.29 g.m-2

CCC estimation: REIP

CCC estimation: REIP

LOO cross-validation:

RMSEP = 0.36 g.m-2

Spatial patterns: LAI

Spatial patterns: LCC

Spatial patterns: CCC

Conclusions

WDVI using Sentinel-2 B4 and B8 at 10 m LAI

CVI using Sentinel-2 B3, B4 and B8 at 10 m LCC

further study on using CVI needed CIgreen using Sentinel-2 B3 and B8 at 10 m CCC

Higher temporal resolution needed for PA: Sentinel-2B launched on 7 March 2017

Thank you for your attention

Questions?

Ref: Remote Sens. 2017, 9, 405; doi:10.3390/rs9050405