VALERI meeting, Avignon, 10 March 2005 Barrax validation agricultural site: Leassons learnt during SPARC campaigns B. Martínez, F. Camacho-de Coca, F.J. García-Haro, A. Verger UIT- Universitat de Valencia F. Baret, M. Weiss INRA - Avignon VALERI meeting. Avignon, 10 March 2005 Universitat de València

VALERI meeting, Avignon, 10 March 2005  OBJECTIVE  TEST SITE AND FIELD CAMPAIGN  TEST SITE CHARACTERIZATION - In-situ measurements - Sampling strategies  TRANSFER FUNCTION: Spatial extension of in-situ measurements  A CASE STUDY WITH LOW RESOLUTION PRODUCTS CONTENTS

VALERI meeting, Avignon, 10 March 2005 Appropriate Ground Data Set LAI/FVC/FAPAR SPARC 2003, 2004 To derive accurate high-resolution maps from in-situ measurements for the validation of (SEVIRI) coarse satellite vegetation products OBJECTIVE Medium and Coarse Biophysical products Agregation of high -resolution maps VALERI methodology Up-scaling High – Resolution biophysical maps Spatial extension of local measurements

VALERI meeting, Avignon, 10 March 2005 CONTENTS  OBJECTIVE  TEST SITE AND FIELD CAMPAIGN  TEST SITE CHARACTERIZATION - In-situ measurements - Sampling strategies  TRANSFER FUNCTION: Spatial extension in-situ measurements  A CASE STUDY WITH LOW RESOLUTION PRODUCTS

VALERI meeting, Avignon, 10 March 2005 Test Site: Barrax (Albacete) Direct Validation: The Barrax agricultural site of 5  5 km2 (‘Las Tiesas’) selected for ground measurements acquisitions. All facilities are available. Indirect Validation: A larger area of 50  50 km2 is selected for inter-comparison and validation of SEVIRI products. Very flat area. Crops and natural vegetation. Two different areas selected: Natural Vegetation Crops Soil

VALERI meeting, Avignon, 10 March 2005 The SPARC campaigns are a combination of different initiatives (ESA, CNES, EU, EUMETSAT) but with the common interest of in-situ characterisation simultaneously to airborne and multi-sensors data acquisitions mainly focused on algorithm and product validation. SPARC’03  from 13th to 14th of July 2003 SPARC’04  from 13th to 17th of July 2004 Our participation was funded by LSA SAF (EUMETSAT) ! Field Campaign: SPARC experiments In situ measurementsAvailable Imagery Gap Fraction (LAI,FVC, FAPAR) Chlorophyll Radiometry Temperature Emisivity Atmospheric profiles ROSIS (1m) ; HyMAP (5m); AHS (2.5m) SPOT/HRV (20m) Landsat/TM (30m) CHRIS/PROBA (34m) MERIS/Envisat (300m-1km) SEVIRI/Meteosat-8 (3 km)

VALERI meeting, Avignon, 10 March 2005  OBJECTIVE  TEST SITE AND FIELD CAMPAIGN  TEST SITE CHARACTERIZATION - In-situ measurements - Sampling strategies  TRANSFER FUNCTION: Spatial extension in-situ measurements A CASE STUDY WITH LOW RESOLUTION PRODUCTS

VALERI meeting, Avignon, 10 March 2005 TEST SITE CHARACTERIZATION: Sampling Strategy Hemispherical camera Sampling design  VALERI methodology. 12 Photographs per ESU GPS was recorded at the center of the ESU LICOR LAI2000 Average of 3 replications 24 measurements per ESU The replications were distributed randomly within the ESU Processed with

VALERI meeting, Avignon, 10 March 2005 TEST SITE CHARACTERIZATION: In-situ measurements

VALERI meeting, Avignon, 10 March Retrieved biophysical parameters TEST SITE CHARACTERIZATION: Results SPARC’03 SPARC’04 LICOR DHP

VALERI meeting, Avignon, 10 March 2005 TEST SITE CHARACTERIZATION: Results 2. Comparison of LICOR and DHP LAI estimates Relative Error between LICOR and DHP mean values per fields. LAI DHP- LICOR Relative error typically <25% FVC DHP- LICOR Relative error <15% for all cases LAI SPARC 2003 A1, A10, P1, G1, ON1 and B3 (downward looking) A9, P1, C2, C1 (upward looking) Camera position: Large relative error found for DOWNWARD LOOKING PHOTOS !

VALERI meeting, Avignon, 10 March Dependent on the camera position TEST SITE CHARACTERIZATION: Results Er(LAI_DW)= 37%Er(LAI_DW)= 57% The estimated LAI can be twice in downward looking position !!! During the SPARC’04 field campaing, all the photographs were taken UPWARD LOOKING when it was possible. Special attention was paid in comparing the results when the camera was in downward and upward looking for some crops. SunflowerCorn

VALERI meeting, Avignon, 10 March 2005 TEST SITE CHARACTERIZATION: Results Attention was paid during SPARC04 in measuring simultaneously with LICOR and DHP. In addition, an intercomparison of different LICORs was done FIELDEr(%) CORN (C1)24% GARLIC (G1)48% POTATO (P)18% SUGARBEET (SB)48% Good agreement between DHP (upward looking) and LICOR estimates. The largest discrepancies found for dens cover (Sugar Beet) are similar to that shown by different LICOR instruments (around 50%). HP vs LICOR LICOR vs LICOR

VALERI meeting, Avignon, 10 March 2005  OBJECTIVE  TEST SITE AND FIELD CAMPAIGN  TEST SITE CHARACTERIZATION - In-situ measurements - Sampling strategies  TRANSFER FUNCTION: Spatial extension in-situ measurements  A CASE STUDY WITH LOW RESOLUTION PRODUCTS

VALERI meeting, Avignon, 10 March 2005 TRANSFER FUNCTION: Spatial Extension to High resolution Transfer Function: Weighted Multiple linear regressions were computed with all possible SPOT bands combinations The band combination was selected based on the lowest RMSEW (Weighted Root Mean Square Error), RCROSS (Cross Validation RMSE) and weights null, following the methodology proposed by Weiss,(2004) LAI FVC FAPAR

VALERI meeting, Avignon, 10 March 2005 TRANSFER FUNCTION: Spatial Extension to High resolution HPLICOR MEAN STD Correlate0.99 Bias0.204 RMS0.263 FVC MEAN0.38 STD0.28 FVCFAPAR MEAN0.46 STD0.33 LAI LICORHP

VALERI meeting, Avignon, 10 March 2005 Influence of Sampling Spatial Strategy CONVEX HULL for DHP Different Samplings Designs White  Interpolated Black  Extrapolated Blue  Considering a relative error of the 5% Transfer Function  FLAG IMAGE Computation of convex hull over the collocated radiance values with the in situ measurements Smallest convex region that contains the data set

VALERI meeting, Avignon, 10 March 2005  OBJECTIVE  TEST SITE AND FIELD CAMPAIGN  TEST SITE CHARACTERIZATION - In-situ measurements - Sampling strategies  TRANSFER FUNCTION: Spatial extension in-situ measurements  A CASE STUDY

VALERI meeting, Avignon, 10 March 2005 Barrax test site (5x5 km) A CASE STUDY: Comparison with large scale products (1 km res) PRODUCTS (10-days composition): VGT_LandSAF_v1  SEVIRI Land SAF algorithm (UV) on VGT k0 data VGT_CYCLOPES_v1 MODIS/TERRA

VALERI meeting, Avignon, 10 March 2005 Leaf Area Index (LAI) In-situ_3km VGT_CYCLOPES_V1 MODIS VGT_LandSAF_V1 Good agreement (RMS 0.85) for both algorithms LSA SAF_V1 and CYCLOPES_V1 on VGT data A CASE STUDY: Comparison with large scale products Barrax large area (50x50 km2)

VALERI meeting, Avignon, 10 March 2005 Fraction of Vegetation Cover (FVC) In-situ_3kmVGT_CYCLOPES_V1VGT_LandSAF_V1 A CASE STUDY: Comparison with large scale products Good agreement (RMS 0.7) for the LSA SAF_v1 algorithm on VGT data Barrax large area (50x50 km2)

VALERI meeting, Avignon, 10 March 2005 In-situ_3km MODISVGT_CYCLOPES_v1 Fraction of Absorbed PAR (FAPAR) A CASE STUDY: Comparison with large scale products Good agreement (RMS 0.8) for MODIS product is found

VALERI meeting, Avignon, 10 March 2005 CONCLUSIONS  Large amount of ground and airborne data has been collected in Barrax from 1998 (DAISEX) up to now (SPARC, DEMETER), and two new ESA field campaigns are planned for 2005 (June and July).  DHP is used for LAI, FVC and FAPAR estimates in addition to LICOR.  The pre-processing with CANEYE has been found quite independent of the operator (UV vs INRA).  However, DHP estimates are dependent on the camera position. Downward looking overestimates the LAI up to 50% regarding Upward looking.  Upward looking shows better consistency with LICOR estimates, with errors not larger than those found between LICORs estimates.  Concerning the spatial extension of in-situ measurements, the best results have been obtained using a transfer function derived from a Weighted Multiple linear regression.  Besides different sampling strategies were performed, the derived high-resolution LAI maps (LICOR and CAMERA) show relatively small differences (RMSE<0.3).  Around 50 units covering the different crops seems to be enough for obtaining a good transfer function for the Barrax test site.

VALERI meeting, Avignon, 10 March 2005 CONCLUSIONS  Comparison of In-Situ degradated maps with different products at 1km and 3km resolution over the small and large area shows that the UV LSA SAF algorithm on VEGETATION data shows the best correlation for FVC and LAI with an RMS < VGT_CYCL-V1< MODIS.  MODIS FAPAR product shows a good agreement (RMS~0.08,r2~0.8).  CYCLOPES products overestimate FVC and LAI, whilst underestimate FAPAR.  Open issues - Derive high-resolution maps for SPARC04 - Assessment of the TF outside the study area (5x5km) - Evaluate different upscaling methods from 20m to 3km  Contact us for: -LAI/FVC/FAPAR data and maps  -SPARC database and new ESA activities 

VALERI meeting, Avignon, 10 March 2005 Thank you for your attention !!

VALERI meeting, Avignon, 10 March 2005 Transfer Function  FLAG IMAGE Computation of convex hull over the collocated radiance values with the in situ measurements Smallest convex region that contains the data set Influence of Sampling Spatial Strategy BIDIMENSIONAL COVEX HULL FOR THE BANDS COMBINATION (GREEN, RED, NIR) RED-GREENNIR-GREENNIR-RED

VALERI meeting, Avignon, 10 March 2005 LAI LICOR (0-5)FVC HP (0-1) fAPAR HP (0-1) AGGREGATION FOR VALIDATE LOW RESOLUTION