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Validation of biophysical produtcs from large swath sensors. F. Baret, M. Weiss*, O. Marloie, N. Bruguier, J.P. Guinot, B. Combal INRA CSE Avignon D. Allard INRA Biométrie Avi - PowerPoint PPT Presentation
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Validation of biophysical produtcs from large swath sensors
F. Baret, M. Weiss*, O. Marloie, N. Bruguier, J.P. Guinot, B. Combal INRA CSE Avignon
D. Allard INRA Biométrie Avi
A. Begué, G. De Wispelaere, C. Lelong, V. Gond, CIRAD MontpellierM. Leroy, E. Mougin, CESBIO Toulouse
J.P. Lagouarde, D. Guyon INRA Bordeaux
J.L. Roujean CNRM Toulouse
S. Rambal, H. Bohbot CEFE Montpellier
T. Nilson, A. Kuusk Tartu Observatory
* Détachée de Noveltis à l'INRA d'Avignon
The project is supported by CNES
CEOS Frascati, 07/05/2001 2/15
Methodology: 5 steps
1. Définition of the spatial sampling strategy
2. Local ground georeferenced measurements of LAI, fAPAR, fCover.
3. Spatial Extension of local measurements using SPOT images
4- Agregation to estimate the biophysical variables at the large swath sensors resolution, and the associated uncertainty.
5- Evaluation of the accuracy of estimates over the ensemble of sites and dates available (including MODLAND)
CEOS Frascati, 07/05/2001 3/15
SITE DISTRIBUTION
VALERI
CEOS Frascati, 07/05/2001 4/15
2001 ScheduleSemaines 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50Alpilles AlpRomilly RomRoumanie Rou RouMali MalLandes Lan LanEstonie EstMontpellier MonBolivie BolArgentine ArgIndonesie IndGuyane Guy MexMexique
LAI 2000-VAL3 Alp Lan Ind Rom Est BolLAI 2000-CSE1 Alp Lan Ind Rom Mon Lan Mal Guy Arg MexLAI2000-CSE4 Rou Rou Mon Lan MalLAI2000-CESBIO EstLAI2000-CEFE Mon Guy Arg MexLAI2000-CIRAD Ind
Niko-CSE1 Alp Lan Rou Mon Bol Mal Guy Arg MexNiko-VAL2 Alp Rou Ind Rom Est LanNiko-VAL2 Bol Mal Guy Arg Mex
GPS-Mag1 Alp Rou RouRom Est Bol Mal ArgGPS-MLR2 Alp Rom MonGPS-VAL3 Ind Mal Guy Arg Mex
Photometre manuel Lan ArgBF2-CSE1 Alp Rou Mon LanBF2-VAL2 Ind Rom Est Bol Mal Guy Arg Mex
2000: 4 sites for methodological developpements2001: 14 opérational sites
CEOS Frascati, 07/05/2001 5/15
What we learned
• Définition of the spatial sampling strategy
• Method to extend local measurements to the whole site
• LAI/fAPAR/fCover Measurements based on hemispherical photos
• Aerosol optical depth measurements based on BF2 systems
CEOS Frascati, 07/05/2001 6/15
Spatial sampling strategy
N (=9) transects of 1km length
Visual notation every 1-4 metres
Detailed measurements on a sub-sample
Continuous landscpe
27 crosses of 12 points: short lagsSpatial distribution and Representation of each classFew transects: medium to long lags
3 Km
3 K
m
Discontinuous landscape
CEOS Frascati, 07/05/2001 7/15
Spatial extension methods
Direct regression Use of a SPOT image:Co-kriging
Results on Alpilles 2001, cross validation
CEOS Frascati, 07/05/2001 8/15
Co-KrigingOrdinary Kriging
Spatial extension methods
LAI maps
CEOS Frascati, 07/05/2001 9/15
Kriging error
Co-Krigeage
Kriging Standard deviation of LAI
Krigeage ordinaire
CEOS Frascati, 07/05/2001 10/15
Choice of the variogramme model
Transects
Crosses
Cross validation
CEOS Frascati, 07/05/2001 11/15
Weight of the spatial information
CEOS Frascati, 07/05/2001 12/15
LAI, fAPAR, fCover measurements: Hemispherical photographs
LAI2000 sampling
Advantages of hémispherical photos•Short vegetation measurements•Better spatial and directional sampling •Less sensitive to illumination conditions •Acces to clumpiness characteristics
CEOS Frascati, 07/05/2001 13/15
Aerosol Characterisation : BF2
Measurement of direct PAR irradiance
•PAR transmittance related to aerosol optical thickness
•Calibration based on Bouguer's line
•Validation of the method based on 3 AERONET sites 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Measured Aerosol Optical Thickness
Est
imae
d A
eros
ol O
ptic
al T
hick
ness
Experimental data1 : 1 line 1 : 1 line
CEOS Frascati, 07/05/2001 14/15
The Web site: www.avignon.inra.fr/valeri
CEOS Frascati, 07/05/2001 15/15
Conclusion
STATUS• Advances in methodological developments• 14 sites sampled in 2001 • Good collaboration with MODLAND (common site, data exchange)
PROBLEMS- Albédo, Chlorophyll? - Transfer function between reflectance and measurements?- Additional funding to go up to the validation of products:
-ESA (MERIS)-PCRD-…