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Barrax validation agricultural site: Leassons learnt during SPARC campaigns

Universitat de València. 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. CONTENTS.

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Barrax validation agricultural site: Leassons learnt during SPARC campaigns

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  1. Universitat de València 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

  2. CONTENTS • 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 VALERI meeting, Avignon, 10 March 2005

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

  4. 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

  5. Natural Vegetation Soil Crops Test Site: Barrax (Albacete) Two different areas selected: 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. VALERI meeting, Avignon, 10 March 2005

  6. Field Campaign: SPARC experiments The SPARC campaigns are a combination of different initiatives (ESA, CNES, EU, EUMETSAT) but with the common interest of in-situ characterisationsimultaneously to airborne andmulti-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) ! VALERI meeting, Avignon, 10 March 2005

  7. 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

  8. Processed with 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 VALERI meeting, Avignon, 10 March 2005

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

  10. TEST SITE CHARACTERIZATION: Results 1.Retrieved biophysical parameters SPARC’03 SPARC’04 LICOR DHP VALERI meeting, Avignon, 10 March 2005

  11. 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 ! TEST SITE CHARACTERIZATION: Results 2.Comparison of LICOR and DHP LAI estimates Relative Error between LICOR and DHP mean values per fields. LAI SPARC 2003 VALERI meeting, Avignon, 10 March 2005

  12. TEST SITE CHARACTERIZATION: Results 3.Dependent on the camera 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. Sunflower Corn Er(LAI_DW)= 37% Er(LAI_DW)= 57% The estimated LAI can be twice in downward looking position !!! VALERI meeting, Avignon, 10 March 2005

  13. 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 HP vs LICOR LICOR vs LICOR 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%). VALERI meeting, Avignon, 10 March 2005

  14. 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

  15. LAI FVC FAPAR 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) VALERI meeting, Avignon, 10 March 2005

  16. LAI FVC FAPAR LICOR HP TRANSFER FUNCTION: Spatial Extension to High resolution VALERI meeting, Avignon, 10 March 2005

  17. Influence of Sampling Spatial Strategy 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 CONVEX HULL for DHP WhiteInterpolated BlackExtrapolated BlueConsidering a relative error of the 5% Different Samplings Designs VALERI meeting, Avignon, 10 March 2005

  18. 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

  19. A CASE STUDY: Comparison with large scale products (1 km res) Barrax test site (5x5 km) 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

  20. A CASE STUDY: Comparison with large scale products Barrax large area (50x50 km2) Leaf Area Index (LAI) MODIS VGT_LandSAF_V1 VGT_CYCLOPES_V1 In-situ_3km Good agreement (RMS<0.25, r2>0.85) for both algorithms LSA SAF_V1 and CYCLOPES_V1 on VGT data VALERI meeting, Avignon, 10 March 2005

  21. A CASE STUDY: Comparison with large scale products Barrax large area (50x50 km2) Fraction of Vegetation Cover (FVC) In-situ_3km VGT_LandSAF_V1 VGT_CYCLOPES_V1 Good agreement (RMS<0.09,r2>0.7) for the LSA SAF_v1 algorithm on VGT data VALERI meeting, Avignon, 10 March 2005

  22. A CASE STUDY: Comparison with large scale products Fraction of Absorbed PAR (FAPAR) In-situ_3km VGT_CYCLOPES_v1 MODIS Good agreement (RMS<0.08, r2>0.8) for MODIS product is found VALERI meeting, Avignon, 10 March 2005

  23. 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

  24. 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 Fernando.Camacho@uv.es -SPARC database and new ESA activities Jose.Moreno@uv.es VALERI meeting, Avignon, 10 March 2005

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

  26. NIR-RED Influence of Sampling Spatial Strategy 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 BIDIMENSIONAL COVEX HULL FOR THE BANDS COMBINATION (GREEN, RED, NIR) RED-GREEN NIR-GREEN VALERI meeting, Avignon, 10 March 2005

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

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