Validation of Global Moderate-Resolution FAPAR Products over Boreal Forests in North America Using Harmonized Landsat and Sentinel-2 Data
Abstract
1. Introduction
2. Study Area and Data
2.1. Study Area and In Situ Data
2.2. Moderate-Resolution FAPAR Products
2.2.1. MODIS and VIIRS FAPAR Products
2.2.2. CGLS FAPAR Products
2.3. The Harmonized Landsat and Sentinel-2 (HLS) Imagery
3. Method
3.1. Derivation of High-Resolution FAPAR from HLS
3.2. Evaluation and Validation of FAPAR Products
4. Results
4.1. High-Resolution Instantaneous FAPAR
4.2. Product Quality Control Information
4.3. Validation of FAPAR Products
5. Discussion
5.1. FAPAR Product Quality
5.2. Uncertainties and Perspectives
6. Conclusions
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Site ID | Names | Type | Latitude | Longitude | Duration | Elevation |
---|---|---|---|---|---|---|
CA–TP4 | Ontario-Turkey Point 1939 Plantation White Pine | Evergreen Forest | 42.7102 | −80.3574 | 2013/12/2–2017/7/14 | 184 m |
CA–TPD | Ontario-Turkey Point Mature Deciduous | Deciduous Forest | 42.6353 | −80.5577 | 2012/1/5–2017/12/31 | 260 m |
US–Bar | Bartlett Experimental Forest | Deciduous Forest | 44.0646 | −71.2881 | 2004/6/10–2017/12/31 | 272 m |
US–HF | Harvard Forest | Deciduous Forest | 42.5353 | −72.1899 | 2011/11/23–2015/8/14 | 351 m |
Product | Sensor | Spatial Resolution | Temporal Resolution | Period | Main Algorithm | Back Up Algorithm | QQFs |
---|---|---|---|---|---|---|---|
MOD15A2H.061 | MODIS | 500 m | 8-day | 2002+ | LUT (red, NIR) | VI (red, NIR) | (1) Main method with best result (2) Main method with good result (saturation) (3) Empirical algorithm used due to bad geometry (4) Empirical algorithm used due to problems other than geometry |
MYD15A2H.061 | |||||||
VNP15A2H v002 | VIIRS | 500 m | 8-day | 2012+ | |||
GEOV2 | PROBA-V | 1 km | 10-day | 1999+ | NN (blue, red, NIR, observation geometry) | Filled with interpolation or climatology | (1) Direct retrieve (not filled) (2) Filled with interpolation (3) Filled with climatology |
GEOV3 | PROBA-V | 1/3 km | 10-day | 2014+ | EBF: NN (blue, red, NIR, observation geometry) Others: Second-degree polynomials fit of the NN result | EBF: Based on previous decadal product Others: Filled by linear fit or nearest data | EBF (1) Based on daily observations (2) Based on previous dekadal product Others: (3) Second-degree polynomials fit (4) Linear fit (5) Interpolation between the two nearest dates within days (6) Nearest data within days |
Parameter | CA-TP4 | CA-TPD/US-HF | US-Bar | ||||
---|---|---|---|---|---|---|---|
Min | Max | Min | Max | Min | Max | ||
Canopy structure | Leaf area index | 0 | 8 | 0 | 7 | 0 | 10 |
Leaf structure parameter | 0.5 | 2.75 | 0.5 | 2.75 | 0.5 | 2.75 | |
Average leaf angle (◦) | 30 | 80 | 10 | 50 | 40 | 80 | |
Leaf property | Chlorophyll A and B (g/cm2) | 10 | 60 | 50 | 80 | 10 | 50 |
Equivalent water thickness (cm) | 0 | 0.2 | 0 | 0.1 | 0 | 0.5 | |
Dry matter content (g/cm2) | 0 | 0.2 | 0 | 0.1 | 0 | 0.2 | |
Soil reflectance coefficient | 0.3 | 1 | 0.3 | 1 | 0.3 | 1 | |
Diffuse fraction | 0.01 | 0.6 | 0.01 | 0.6 | 0.01 | 0.6 |
Metrics | Explanation | Interpretation | |
---|---|---|---|
RMSE | Overall uncertainty | (2) | |
Bias | Accuracy | (3) | |
SD | Precision | (4) | |
R | Strength of relationship between two variables | (5) | |
P | Percentage of pixels meeting requirements | PO: Percentage of pixels meeting the optimal requirements of the CGLS and the goal requirements of the GCOS PT: Percentage of pixels meeting the target requirements of the CGLS and the threshold requirements of the GCOS |
Sites | Products | Pixel-Level Comparison | Plot-Level Comparison | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
R | RMSE | Bias | SD | PO (%) | PT (%) | R | RMSE | Bias | SD | PO (%) | PT (%) | ||
(a) CA-TP4 | MOD | 0.63 | 0.22 | −0.16 | 0.16 | 27.91 | 49.30 | 0.85 | 0.21 | −0.16 | 0.12 | 16.84 | 42.11 |
MYD | 0.58 | 0.24 | −0.17 | 0.17 | 27.29 | 49.01 | 0.75 | 0.24 | −0.19 | 0.15 | 10.53 | 38.95 | |
VNP | 0.63 | 0.22 | −0.15 | 0.16 | 31.30 | 50.99 | 0.84 | 0.21 | −0.17 | 0.13 | 9.47 | 46.32 | |
GEOV2 | 0.70 | 0.22 | −0.16 | 0.15 | 28.72 | 40.78 | 0.85 | 0.21 | −0.17 | 0.12 | 1.47 | 30.88 | |
GEOV3 | 0.81 | 0.20 | −0.16 | 0.12 | 14.71 | 38.48 | 0.74 | 0.22 | −0.17 | 0.14 | 24.53 | 41.51 | |
(b) CA-TPD | MOD | 0.78 | 0.16 | −0.07 | 0.14 | 39.20 | 58.81 | 0.89 | 0.12 | −0.07 | 0.1 | 34.48 | 59.77 |
MYD | 0.81 | 0.16 | −0.09 | 0.14 | 37.14 | 56.39 | 0.89 | 0.14 | −0.08 | 0.11 | 32.18 | 57.47 | |
VNP | 0.84 | 0.13 | −0.05 | 0.12 | 44.32 | 65.48 | 0.93 | 0.1 | −0.05 | 0.09 | 52.87 | 74.71 | |
GEOV2 | 0.84 | 0.12 | −0.04 | 0.12 | 34.05 | 52.97 | 0.89 | 0.13 | −0.08 | 0.1 | 33.33 | 58.73 | |
GEOV3 | 0.86 | 0.13 | −0.08 | 0.11 | 35.09 | 62.41 | 0.91 | 0.12 | −0.06 | 0.11 | 34.78 | 52.17 | |
(c) US-Bar | MOD | 0.63 | 0.22 | −0.15 | 0.15 | 34.06 | 53.29 | 0.79 | 0.21 | −0.16 | 0.14 | 21.47 | 49.44 |
MYD | 0.63 | 0.21 | −0.14 | 0.15 | 34.61 | 56.51 | 0.76 | 0.21 | −0.16 | 0.14 | 18.08 | 51.98 | |
VNP | 0.65 | 0.21 | −0.14 | 0.15 | 35.85 | 57.51 | 0.80 | 0.2 | −0.15 | 0.13 | 20.62 | 54.52 | |
GEOV2 | 0.71 | 0.19 | −0.14 | 0.14 | 39.25 | 53.35 | 0.75 | 0.21 | −0.17 | 0.13 | 22.14 | 44.66 | |
GEOV3 | 0.71 | 0.20 | −0.15 | 0.13 | 28.56 | 47.81 | 0.75 | 0.19 | −0.14 | 0.13 | 43.65 | 54.31 | |
(d) US-HF | MOD | 0.78 | 0.14 | −0.06 | 0.13 | 41.47 | 60.24 | 0.88 | 0.11 | −0.06 | 0.09 | 51.40 | 67.60 |
MYD | 0.77 | 0.13 | −0.06 | 0.12 | 40.59 | 59.59 | 0.85 | 0.12 | −0.07 | 0.1 | 43.58 | 64.80 | |
VNP | 0.78 | 0.13 | −0.05 | 0.11 | 41.56 | 61.64 | 0.90 | 0.09 | −0.05 | 0.07 | 52.51 | 70.95 | |
GEOV2 | 0.90 | 0.11 | −0.06 | 0.09 | 41.68 | 56.74 | 0.92 | 0.09 | −0.06 | 0.07 | 40.60 | 61.65 | |
GEOV3 | 0.88 | 0.11 | −0.06 | 0.08 | 32.16 | 57.01 | 0.93 | 0.1 | −0.06 | 0.09 | 43.27 | 55.77 | |
(e) mean | MOD | 0.71 | 0.19 | −0.11 | 0.15 | 35.66 | 55.41 | 0.85 | 0.16 | −0.11 | 0.11 | 31.05 | 54.73 |
MYD | 0.70 | 0.19 | −0.12 | 0.15 | 34.91 | 55.38 | 0.81 | 0.18 | −0.13 | 0.13 | 26.09 | 53.30 | |
VNP | 0.73 | 0.17 | −0.10 | 0.14 | 38.25 | 58.90 | 0.87 | 0.15 | −0.11 | 0.11 | 33.87 | 61.62 | |
GEOV2 | 0.79 | 0.16 | −0.10 | 0.13 | 35.93 | 50.96 | 0.85 | 0.16 | −0.12 | 0.11 | 24.39 | 48.98 | |
GEOV3 | 0.82 | 0.16 | −0.11 | 0.11 | 27.63 | 51.43 | 0.83 | 0.16 | −0.11 | 0.12 | 36.56 | 50.94 |
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Zhang, Y.; Fang, H.; Hu, Z.; Wang, Y.; Li, S.; Wu, G. Validation of Global Moderate-Resolution FAPAR Products over Boreal Forests in North America Using Harmonized Landsat and Sentinel-2 Data. Remote Sens. 2025, 17, 2658. https://doi.org/10.3390/rs17152658
Zhang Y, Fang H, Hu Z, Wang Y, Li S, Wu G. Validation of Global Moderate-Resolution FAPAR Products over Boreal Forests in North America Using Harmonized Landsat and Sentinel-2 Data. Remote Sensing. 2025; 17(15):2658. https://doi.org/10.3390/rs17152658
Chicago/Turabian StyleZhang, Yinghui, Hongliang Fang, Zhongwen Hu, Yao Wang, Sijia Li, and Guofeng Wu. 2025. "Validation of Global Moderate-Resolution FAPAR Products over Boreal Forests in North America Using Harmonized Landsat and Sentinel-2 Data" Remote Sensing 17, no. 15: 2658. https://doi.org/10.3390/rs17152658
APA StyleZhang, Y., Fang, H., Hu, Z., Wang, Y., Li, S., & Wu, G. (2025). Validation of Global Moderate-Resolution FAPAR Products over Boreal Forests in North America Using Harmonized Landsat and Sentinel-2 Data. Remote Sensing, 17(15), 2658. https://doi.org/10.3390/rs17152658