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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. - PowerPoint PPT Presentation
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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 2005Universitat
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
-sca
lin
g
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 55 km2 (‘Las Tiesas’) selected for ground measurements acquisitions. All facilities are available.
Indirect Validation: A larger area of 5050 km2 is selected for inter-comparison and validation of SEVIRI products. Very flat area. Crops and natural vegetation.
Two different areas selected:
Natural Vegetation
CropsSoil
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 2003SPARC’04 from 13th to 17th of July 2004
Our participation was funded by LSA SAF (EUMETSAT) !
Field Campaign: SPARC experiments
In situ measurements Available 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
CROPS FIELDS ESUs_LAI2000 FIELDS ESUs_CAMERA CORN 7 21 4 10
ALFALFA 6 19 3 16 SUGAR BEET 4 19 1 6
ONION 2 16 2 2 GARLIC 1 11 1 2 POTATO 1 14 1 6
VINEYARD 0 0 1 1 GRASS 0 0 1 6
FRUIT TREES 0 0 2 2 TOTAL 21 100 16 53
CROP FIELDS_LAI2000 ESUs_LAI2000 FIELDS_HP ESUs_HP Corn 6 19 6 7
Alfalfa 6 22 6 6 Sugarbeet 2 20 4 5
Onions 3 12 6 8 Garlic 2 17 1 4 Potato 3 16 3 4
Vineyard 1 4 2 4 Sunflower 3 27 1 3
Forest 0 0 1 4 Grass 0 0 1 1 TOTAL 26 137 31 46
Processed with
VALERI meeting, Avignon, 10 March 2005
TEST SITE CHARACTERIZATION: In-situ measurements
VALERI meeting, Avignon, 10 March 2005
1. Retrieved biophysical parameters
TEST SITE CHARACTERIZATION: Results
0
5
10
15
20
25
0 0,8 1,6 2,4 3,2 4 4,8 5,6 6,4
CO
UN
TS
LAI
LAI from LICORSPARC03
0
2
4
6
8
10
0 0,8 1,6 2,4 3,2 4 4,8 5,6
CO
UN
TS
LAI
LAI from HPSPARC03
0
2
4
6
8
10
0 0,8 1,6 2,4 3,2 4 4,8 5,6
CO
UN
TS
LAI
LAI from HP SPARC04
0
5
10
15
20
25
0 0,8 1,6 2,4 3,2 4 4,8 5,6
Cou
nt
LAI
CO
UN
TS
LAI from LICORSPARC04
SPARC’03 SPARC’04
LIC
OR
DH
P
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
-100
-75
-50
-25
0
25
50
75
100
A9 A1 A10 P1 C2 C1 G1 B3 ON1
Err
or
Re
lati
vo
(%
)
CULTIVOS
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 2005
3. 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.
Sunflower Corn
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
-100
-75
-50
-25
0
25
50
75
100
SB1 SB1 SB C C ON ON
Er(effective-LICOR)
Er(
%)
CROP
FIELD Er(%)
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 LICORLICOR 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)
Instrument (G, R, NIR) INTERCEPT RMSE RMSEW RCROSS
LI-COR -0.011 -0.014 0.021 0.7 0.61 0.54 0.61
HP -0.004 -0.019 0.016 1.5 0.71 0.48 0.70
LAI
Instrument NDVI INTERCEPT RMSE RMSEW RCROSS LI-COR 1.46 0.034 0.13 0.11 0.14
HP 1.41 0.030 0.18 0.17 0.16
FVC
Instrument NDVI INTERCEPT RMSE RMSEW RCROSS HP 1.46 0.1 0.17 0.10 0.18
FAPAR
VALERI meeting, Avignon, 10 March 2005
TRANSFER FUNCTION: Spatial Extension to High resolution
HP LICOR
MEAN 1.91 1.71
STD 1.48 1.62
Correlate 0.99
Bias 0.204
RMS 0.263
FVC
MEAN 0.38STD 0.28
FVC FAPAR
FAPAR
MEAN 0.46STD 0.33
LAI
LICOR HP
VALERI meeting, Avignon, 10 March 2005
Influence of Sampling Spatial Strategy
CONVEX HULL for DHP
Different Samplings Designs
WhiteInterpolatedBlack ExtrapolatedBlue Considering a relative error of the 5%
Transfer Function FLAG IMAGEComputation 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 5x5 km2
0
0,1
0,2
0,3
0,4
0,5
0,6
IN-SITU VGT_LandSAF VGT_CYCL
FV
C mean
std
Barrax test site (5x5 km)
A CASE STUDY: Comparison with large scale products (1 km res)
Barrax 5x5 km2
0
0,1
0,2
0,3
0,4
0,5
IN-SITU MODIS VGT_CYCL
FA
PA
Rmean
std
PRODUCTS (10-days composition):
VGT_LandSAF_v1 SEVIRI Land SAF algorithm (UV) on VGT k0 data
VGT_CYCLOPES_v1
MODIS/TERRA
Barrax 5x5 km2
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
2
IN-SITU VGT_LandSAF VGT_CYCL MODIS
LA
I
mean
std
VALERI meeting, Avignon, 10 March 2005
Leaf Area Index (LAI) In-situ_3km VGT_CYCLOPES_V1 MODISVGT_LandSAF_V1
Good agreement (RMS<0.25, r2>0.85) for both algorithms LSA SAF_V1 and CYCLOPES_V1 on VGT data
A CASE STUDY: Comparison with large scale productsBarrax large area (50x50 km2)
VALERI meeting, Avignon, 10 March 2005
Fraction of Vegetation Cover (FVC)
In-situ_3km VGT_CYCLOPES_V1VGT_LandSAF_V1
A CASE STUDY: Comparison with large scale products
Good agreement (RMS<0.09,r2>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<0.08, r2>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 [email protected] database and new ESA activities [email protected]
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-GREEN NIR-GREEN NIR-RED
VALERI meeting, Avignon, 10 March 2005
LAI LICOR (0-5) FVC HP (0-1) fAPAR HP (0-1)AGGREGATION FOR VALIDATE LOW RESOLUTION