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Science Review Panel Meeting Biosphere 2, Tucson, AZ - January 4-5, 2011 Vegetation Phenology and Vegetation Index Products from Multiple Long Term Satellite Data Records Cross-Sensor Continuity Science Algorithm Tomoaki Miura and Javzan Tsend-Ayush Alex Dale (M.S. Graduate Student) Joshua Turner (Federal Work Study Student) University of Hawaii at Manoa NASA MEASURES #NNX08AT05A
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Factors Affecting Cross-Sensor Continuity & Considered in Science Algorithm 1. Spectral bandpass 2. Spatial resolution (point spread function) 3. Algorithm 4. Sun-target-view geometry MEASURES VIP ESDRs Science Review Panel -2-
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Science Algorithm – Two Approaches I. Top-down, direct image comparison using overlapping period of observation (Javzan Tsend-Ayush & Alex Dale) Derivation of multi-sensor translation equations Development of an evaluation methodology II. Bottom-up, simulation analysis using hyperspectral imagery (Tomoaki Miura & Joshua Turner) Derivation of multi-sensor translation equations Characterization of factorial effects, error budgets MEASURES VIP ESDRs Science Review Panel -3-
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Methods for Deriving Multi-sensor Translation Equations 1. Spatial aggregation to the CMG (.05 o ) grid 2. Data screening on a per-pixel basis 3. Extraction of a random sample 4. Regression analysis to derive equations I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -4-
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2. Data Screening I. Screening - SM - Cloud - Shadow SPOT-4 VEGETATION - 1998,1999, 2001, 2002 Terra MODIS - 2001, 2002 AVHRR LTDR. ver2 -1998, 1999 I. Screening - QA -Cloudy -Partly Cloudy -Shadow I. Screening - QA -Cloudy -Fire -Dust -Cloud shadow, … I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -5-
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2. Data Screening Water mask from 2001 expanded by one pixel I. Top-down, Direct Image Comparison (Chen, 1999) MEASURES VIP ESDRs Science Review Panel -6-
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2. Data Screening 0 1 11 21 31 41 51 61 71 81 91 100 0 165 Number of clear observations Percent difference between -5 and 5 Percent difference less than -45 Percent difference larger than 45 I. Top-down, Direct Image Comparison % total observations MEASURES VIP ESDRs Science Review Panel-7-
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3. Sample Preparation I. Top-down, Direct Image Comparison VGT4-NDVI vs. AVH14 – NDVI MEASURES VIP ESDRs Science Review Panel -8-
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MODIS-NDVI vs VGT-NDVI ( 40 percent of all datasets ) I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -9-
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Footprint Simulation Changes in footprint size and PSF modeled using a satellite orbital model (Tan et al., 2006) Daily basis over a 16-day period in June 2002 Terra MODIS 250m/500m at nadir NOAA-16 AVHRR 1.1 km at nadir SPOT-4 VEGETATION 1.1 km at nadir Satellite Center of the Earth MEASURES VIP ESDRs Science Review Panel -10-
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AVHRR Off Nadir vs Nadir 1: View Zenith Angle Effects MEASURES VIP ESDRs Science Review Panel -11-
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AVHRR Off Nadir vs Nadir Geolocation Error (m) X=-480, Y=30 (Angle=55) X=540, Y=-900 (Angle=5) 2: Geolocation Error Effects MEASURES VIP ESDRs Science Review Panel -12-
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Sensor Comparison ~ NDVI DOY=175 DOY=181 MOD500 = 26º(X=-2, Y=0), AVH16 = 43º (X=0, Y=-8), VGT = 50º (X=1, Y=-6) MOD500 = 37º(X=1, Y=-1), AVH16 = 45º (X=-27, Y=-18), VGT = 36º (X=68, Y=-15) 2: View Zenith Angle & Geolocation Error Effects (Miura et al., 2010, in prep.) MEASURES VIP ESDRs Science Review Panel -13-
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NDVI MOD500 vs VGT MOD500 vs AVH16 VGT vs AVH16 3: Pixel Averaging EVI MEASURES VIP ESDRs Science Review Panel -14-
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4. Regression Analysis Regression Analysis Ordinary Least Square Geometric Mean Functional Relationship Least Median of Square Agreement Analysis Mean product-difference RMSD of systematic and unsystematic Agreement coefficient Error Analysis Classified percentage error and visual interpretation I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -15-
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4. Regression Analysis I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -16-
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4. Regression Analysis Deriving translation equations - Least square regression technique (95% confidence). 80 % of the paired observations were used. Single Equation: All samples with all land cover types Stratification Method-3: based on the phenological region map (2956 classes ) Stratification Method-2: based on the Landcover map & latitudinal zoning Stratification Method-1 : based on the Landcover map( 15 of IGBP 17 classes) Land stratification methods were examined for minimizing each VI differences across multi-sensors I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -17-
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IGBP Land cover map (MODIS 2001) Water Evergreen Needleleaf forest Evergreen Broadleaf forest Deciduous Needleleaf forest Deciduous Broadleaf forest Mixed forest Closed shrublands Open shrublands Woody savannas Savannas Grasslands Permanent wetlands Croplands Urban and built-up Cropland/Natural vegetation mosaic Snow and ice Barren/sparsely vegetated I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -18-
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Result of Stratification method-2 Water Evergreen Needleleaf forest Evergreen Broadleaf forest Deciduous Needleleaf forest Deciduous Broadleaf forest Mixed forest Closed shrublands Open shrublands Woody savannas Savannas Grasslands Permanent wetlands Croplands Urban and built-up Cropland/Natural vegetation mosaic Snow and ice Barren/sparsely vegetated 30 o I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -19-
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Result of Stratification method-3 A phenological region map derived from MODIS data (2956 classes) I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -20-
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Comparison of Stratifications I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -21-
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MODIS-NDVI vs VGT-NDVI ( 40 percent of all datasets ) I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -22-
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MOD-NDVI vs VGT-NDVI ( the same direction of viewing and difference VZA is less than 10 degree) I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -23-
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LC-1 LC-2 LC-3 LC-4 LC-5 LC- 6 LC-7 LC-8 LC-9 LC-10 LC-11 LC-12 LC-13 LC-14 LC-15 MOD-EVI2 vs VGT-EVI2 I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -24-
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Translation Equations Derived from the Top-down Analyses I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -25-
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Translation Equations Derived from the Top-down Analyses (cont.) I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -26-
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Translation Equations Derived from the Top-down Analyses (cont) I. Top-down, Direct Image Comparison MEASURES VIP ESDRs Science Review Panel -27-
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Locations of Study Sites II. Bottom-up, Hyperspectral Simulation Analysis MEASURES VIP ESDRs Science Review Panel -28-
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1. Spectral Compatibility – NDVI II. Bottom-up, Hyperspectral Simulation Analysis MEASURES VIP ESDRs Science Review Panel -29-
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1. Spectral Compatibility – EVI2 II. Bottom-up, Hyperspectral Simulation Analysis MEASURES VIP ESDRs Science Review Panel -30-
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2. Scaling Uncertainties between CMG and GAC Resolutions II. Bottom-up, Hyperspectral Simulation Analysis MEASURES VIP ESDRs Science Review Panel -31-
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3. Atmospheric Correction - NDVI II. Bottom-up, Hyperspectral Simulation Analysis MEASURES VIP ESDRs Science Review Panel -32-
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Evaluation Methods Derived VIs translation equations are applied to translate AVHRR VIs to “SPOT4 Vegetation-like” VIs SPOT4 Vegetation VIs to “MODIS-like” VIs Validation: 20 % of the paired observations were used where: is an estimator of parameter MEASURES VIP ESDRs Science Review Panel -33-
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Agreement Analysis & Coefficient (Ji & Gallo, 2006) The agreement coefficient (AC) considers that both x- and y- variables are subject to random errors. The AC measures the systematic (RMPD S ) and unsystematic (RMPD U ) components of the root mean square difference (RMSD): RMPD S RMPD U MEASURES VIP ESDRs Science Review Panel -34-
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Global Coarse Resolution (0.05 o ) Daily Products: Terra MODIS vs. SPOT-4 VEGETATION Sensor (Y vs. X)RMPD S (RMPD U )GMFRR2R2 Original (5%) MOD vs. VGT4.025(±.045)Y =.016 +1.034 X.95 Translated (5%) MOD vs. ML-VGT4<.001(±.043)Y = -.001 +1.004 X.95 NDVI Sensor (Y vs. X)RMPD S (RMPD U )GMFRR2R2 Original (5%) MOD vs. VGT4.027(±.032)Y =.010 +1.102 X.91 Translated (5%) MOD vs. ML-VGT4.001(±.032)Y = -.002 +1.010 X.91 EVI2 (Tsend-Ayush et al., 2010, in prep.) MEASURES VIP ESDRs Science Review Panel -35-
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Error Analysis 0 240 Min 1 max 241 Cluster -45 100*(vgt-avh)/vgt 0 1 11 21 31 41 51 61 71 81 91 100 Cluster 45 Cluster 0 MEASURES VIP ESDRs Science Review Panel -36-
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-0.05≤ Mod_NDVI – ModLikeVGT_NDVI < 0.05 MEASURES VIP ESDRs Science Review Panel -37-
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-0.05≤ Mod_EVI2 – ModLikeVGT_EVI2 < 0.05 MEASURES VIP ESDRs Science Review Panel -38-
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Root Mean Square Difference of VGT-NDVI and MODIS-NDVI MEASURES VIP ESDRs Science Review Panel -39-
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Root Mean of Square Difference of VGT-EVI2 and MODIS-EVI2 MEASURES VIP ESDRs Science Review Panel -40-
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Current Issues & Future Work LTDR AVHRR algorithm improvements BRDF-adjustment Aerosol correction Terra vs. Aqua comparisons [to establish error bounds] Expansion of geographic & temporal coverage MEASURES VIP ESDRs Science Review Panel -41-
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