Collaborative research project pre agro

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Collaborative research

project

pre agro

Extraction of phenology-dependent

structural information from

hyperspectral, directional CHRIS data

for a better derivation of canopy

parameters of winter-wheat

Vista Geowissenschaftliche Fernerkundung GmbH

Silke Begiebing, Heike Bach, Wolfram Mauser

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CHRIS Workshop 2006, Silke Begiebing

Content

• The preagro project

• Overview on hyperspectral remote sensing data and test-sites

• Concept of the model based analyses • Derivation of canopy parameters

• Resulting maps for green LAI and fraction of senescent material

• Validation

• Summary and first results of data assimilation into the crop growth model

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The preagro project

preagro is a German project for joint research and development of basics for precision agriculture:

preagro is a German project for joint research and

development of basics for precision agriculture:

„Information driven crop production with precision farming as the central scientific and technical

precondition for a sustainable development of agricultural land use.“

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The preagro project

• Preagro is Germany’s largest activity in the field of precision agriculture

• coordinated by Dr. A. Werner, ZALF

• Funded by the German Federal Ministry of Education and Research

• VISTA is in charge for remote sensing applications of hyperspectral data using…

• Multitemporal directional CHRIS observations • Multitemporal airborne hyperspectral

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Overview on the hyperspectral remote sensing data

Used for derivation of... • plant structure

• green Leaf Area Index • fraction of mature material Used for derivation of...

• plant structure

• green Leaf Area Index • fraction of mature material

CHRIS CHRIS North +55° +36° 0° -36° -55° Ground Track Sun

Used for derivation of... • green Leaf Area Index • fraction of mature material • upscaling analyses

AVIS

Available ground truth:

• soil maps

• biomass measurements

• LAI measurements with LICOR 2000 • yield maps

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Suitable CHRIS data 2005 / 2006

Year Date Test-site Phenological state

2005 Apr 04 Wulfen / Baasdorf Tillering wheat

Jun 19 Wulfen / Baasdorf Milk stage wheat

Jul 24 Groß-Twülpstedt Used for soil parameterisation

Aug 19 Groß-Twülpstedt Used for soil parameterisation

2006 Apr 14 Wulfen / Baasdorf Tillering wheat

Jun 12 Wulfen / Baasdorf Flowering wheat

Jun 13 Groß-Twülpstedt Flowering wheat

Sep 07 Wulfen / Baasdorf Milk stage maize

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Test-site Wulfen / Baasdorf

CHRIS data: 36m ground resolution (Mode 1) CHRIS data: 36m ground resolution (Mode 1) Air-borne data: 2m ground resolution

Red edge - color composit Red edge - color composit

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Test-site Groß-Twülpstedt

AVIS data: 4m ground resolution

CHRIS data: 18m ground resolution (Mode 5)

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Example of a coupled ecosystem and radiative transfer model

Daily simulation of LAI and biomass accumulation

Daily simulation of reflectance

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Derivation of plant parameters for a single spectrum

Parameter adjustment

Comparison of simulated and measured reflectance

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Spatial demonstration of parameter retrieval

Measured spectral patterns

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Four-Stream Radiative Transfer Model SLC (Verhoef & Bach 2003)

Input parameters:

Soil BRDF parameters (b, c, B0, h) Dry soil reflectance spectrum Soil moisture

Solar zenith angle

Observation zenith angle Relative azimuth angle

Fraction diffuse sky irradiance

Leaf chlorophyll Leaf water Leaf dry matter

Leaf mesophyll structure

LAI – leaf area index

Leaf angle distribution

Hot spot parameter

Fraction of mature material

Dissociation factor: green / brown Crown coverage

Fluxes considered : 1. Direct solar flux

2. Diffuse downward flux 3. Diffuse upward flux

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BRDF sensitivity to average leaf angle

Î Spectral changes at 5 observation zenith angles with structural change

SLC input: green LAI = 4 SLC input: green LAI = 4

60° 0 10 20 30 40 50 60 0.45 0.65 0.85 1.05 wavelength [µm] reflectance [%] -55° -36° 0° +36° +55° 70° 60° 0 10 20 30 40 50 60 0.45 0.65 0.85 1.05 wavelength [µm] reflectance [%] -55° -36° 0° +36° +55° 80° 60° 70° 0 10 20 30 40 50 60 0.45 0.65 0.85 1.05 wavelength [µm] reflectance [%] -55° -36° 0° +36° +55°

Average leaf angle

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BRDF sensitivity analyses change of leaf angle

(modelled)

BRDF at 780nm simulated for different leaf angles

0.8 1 1.2 1.4 1.6 1.8 2 -60 -40 -20 0 20 40 60 observer zenith [°]

BRDF factor related to nadir

60° 70° 80° 0.8 1 1.2 1.4 1.6 1.8 2 -60 -40 -20 0 20 40 60 observer zenith [°]

green maturing senescent

BRDF at 780nm measured at different monitoring points

CHRIS, Jun 21th 05 CHRIS, Jun 21th 05 SLC input: total LAI = 4

SLC input: total LAI = 4

0.8 1 1.2 1.4 1.6 1.8 2 -60 -40 -20 0 20 40 60 observer zenith [°]

60° 70° + 50% fB 80° + 80% fB 60° 70° 80° maturing (measured)

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Structural change with phenology

Î Structure changes as dominance of stems and heads increases with maturing

CONSTANT

Average angle leaves: 52°

Average angle heads & stems:

82°

VARIABLE

Average leaf angle over canopy: ?

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Derivation of structure from directional CHRIS data

CHRIS data Jun 19th 2005 Î during maturing

process

ÎInversion of SLC using all 5 observation zeniths for different leaf angles.

Result: Linear coupling between fraction of mature

material and leaf angles:

0% senescent average leaf angle 63° 100% senescent average leaf angle 78°

63° 67° 70° 74° 78°

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Winter wheat, comparison between AVIS

and CHRIS acquisitions (Jun 19th/21th 2005)

Shown area: approx. 130ha Shown area: approx. 130ha

Visible color composit

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Derived fraction of mature material and green LAI from CHRIS data (Jun 19th)

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Derivated fraction of mature material and green LAI from AVIS data (Jun 21th)

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Validation of the derived parameters (airborne data)

Fraction of mature material

Fraction of mature material Green / Total LAI _{Green / Total LAI}

0 20 40 60 80 100 0 20 40 60 80 100

fraction of mature material from photo analyses [% ] 22.06.05 mo d e ll e d fr a c ti o n o f m a tu re m a te ri a l [%] 21. 06. 05 RMSE = 15.5% _{y = 0.9457x - 1.684} R2 = 0.8446 0 1 2 3 4 5 2 3 4 5 6 7

Licor LAI measurements [m²/m²] 20.06.05

m ode ll e d gr e e n L A I [ m ²/ m ²] 2 1 .0 6 .0 5

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Summary

• Green Leaf Area Index as well as fraction of mature material could successfully be retrieved from airborne and spaceborne hyperspectral remote sensing data

• Incorporation of phenological development is important for correct structural parametrisation; this was

accomplished by using the directional CHRIS data

• Work in progress: data assimilation into the crop growth model PROMET-V for yield modelling

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First assimilation into crop growth model

10 : 90 30 : 110

Average modelled yield : 45 dt/ha

Average modelled yield :

45 dt/ha

Average measured yield : 65 dt/ha

Average measured yield :

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Acknowledgements

Thanks to

• support by BMBF within the project PreAgro (FK 0330679)

...and to you for your attention!

Contact:

Silke Begiebing, Dr. Heike Bach

Vista Geowissenschaftliche Fernerkundung GmbH

Gabelsbergerstr.51, 80333 München, Germany ++49 (0)89 / 52 38 98 03

http://www.vista-geo.de

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Ableitung der Blattwinkel aus Fotos

Monitoringpunkt 3 Schlag 141, Foto von TP14

mittl. Wkl. mittl. Wkl. Blätter Stiele/Ähren Winkel Juni: Mittelwert insg.: 52.3508729 82.26737452 Mittelwert Grün: 54.5024151 81.79418901 Mittelwert Braun: 50.1993307 82.74056003 Winkel Juli: Mittelwert insg.: 51.5408541 81.87310542 Mittelwert Grün: 54.9788562 81.46813235 Mittelwert Braun: 48.6758524 82.21058298

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CHRIS Workshop 2006, Silke Begiebing 25 TP 13: Gekoppelte Modellierung Plausible Wertebereiche Optimierung interner Modell-parameter Simulierter LAI, Chlorophyll, … Bestandswachs-tumsmodell PROMET-V Geo-biophysikal. Karten Meteodaten, Landnutzung, GIS-Info Biomasse, Kornertrag, N-Aufnahme Pflanzenwasser... Aus Fernerkundung abgeleiteter LAI, Chlorophyll, ... Bestandes-reflexionsmodell SLC Inversion von SLC Modelliertes Reflexions-spektrum Anpassung von LAI, Chlorophyll,… Hyperspek-traldaten Kalibrierung & Atmosphären-korrektur Beobachtetes Reflexions-spektrum

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Fotoanalyse I

Anteil seneszenten Materials aus Photoanalyse

Î Spectral index

Anteil seneszenten Materials aus Photoanalyse

Î Spectral index Monitoringpunkt 3 Schlag 141, Foto von TP14 Monitoringpunkt 3 Schlag 141, Foto von TP14 green senescent green senescent 16,5% fraction mature 16,5% fraction mature

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BRDF sensitivity analyses

Î BRDF change with maturing

BRDF at 780nm simulated for different leaf angles

0.8 1 1.2 1.4 1.6 1.8 2 -60 -40 -20 0 20 40 60 observer zenith [°]

60° 70° 80° 0.8 1 1.2 1.4 1.6 1.8 2 -60 -40 -20 0 20 40 60 observer zenith [°]

green maturing senescent

BRDF at 780nm measured at different monitoring points

CHRIS, Jun 21th 05 CHRIS, Jun 21th 05 SLC input: total LAI = 4

SLC input: total LAI = 4

0.8 1 1.2 1.4 1.6 1.8 2 -60 -40 -20 0 20 40 60 observer zenith [°]

60°

70° + 50% fB 80° + 80% fB

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Overview on the hyperspectral remote sensing data

Used for derivation of... • plant structure

• green Leaf Area Index • Fraction of mature material Used for derivation of...

• plant structure

• green Leaf Area Index • Fraction of mature material

CHRIS CHRIS North +55° +36° 0° -36° -55° Ground Track Sun

Used for derivation of... • green Leaf Area Index • Fraction of mature material • upscaling analyses

AVIS

Sensitive for: • green leaf area index

• fraction of mature material • chlorophyll content

• plant water content • plant structure

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Correlation to yield measurements

y = 0.0497x - 0.8286 R2 = 0.8276 0 1 2 3 4 5 30 50 70 90 110 Ertrag [dt/ha]

modellierter grüner LAI [m²/m²

] 21.06.05 Yield [dt/ha] Yield [dt/ha] Modelled green LAI [m²/m²] 21.06.05 Modelled green LAI [m²/m²] 21.06.05

Î good basis for yield modelling