Researching | Calibration Site BRDF Modeling Method Based on Ground and Low-Altitude UAV Joint Observation

Acta Optica Sinica, Volume. 43, Issue 15, 1528001(2023)

Calibration Site BRDF Modeling Method Based on Ground and Low-Altitude UAV Joint Observation

Yuqing He^1、*, Wenjie Hu^1、**, Xiuqing Hu^2,3、***, Jibiao Zhu², Xingwei He^2,3, and Weiqi Jin¹

Author Affiliations

¹Key Laboratory of Photoelectronic Imaging Technology and System, Ministry of Education, School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China

²Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites, National Satellite Meteorological Center (National Center for Space Weather), China Meteorological Administration, Beijing 100081, China

³Innovation Center for FengYun Meteorological Satellite (FYSIC), Beijing 100081, China

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References (18)

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Figures & Tables(20)

Fig. 1. Components and observing mode of the BRDF measurement system

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Fig. 2. Ground-based synchronous measurement system. (a) Ground-based spectrometer measurement system; (b) shading board; (c) solar radiometer; (d) all-sky imager

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Fig. 3. Relationship between calibration coefficients of the reference panel and illumination angles

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Fig. 4. Spectral radiance of each target observed synchronously by the airborne-ground observation system

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Fig. 5. Surface features of field targets at different scales. (a) Satellite observation; (b) UAV observation; (c) ground observation

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Fig. 6. Spatial distribution of target reflectance in the 555 nm band measured by the airborne spectrometer

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Fig. 7. Measurement data of the ground-based spectrometer. (a) Variation of solar irradiance throughout the day; (b) variation of diffuse-to-total irradiance ratio throughout the day

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Fig. 8. Relationship between spectral angle and wavelength shift between airborne and ground-based spectrometers

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Fig. 9. Surface reflectance calculated before and after wavelength shift correction. (a) Before wavelength shift correction; (b) after wavelength shift correction

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Fig. 10. Comparison of surface reflectance calculated by single and dual spectrometer method. (a) Calculation with a single spectrometer; (b) calculation with a dual spectrometer; (c) reflectance at 61 points in the 555 nm band

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Fig. 11. Spatial distribution maps of ANIF at the 555 nm, 858 nm, and 1240 nm bands

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Fig. 12. Changes in atmospheric environment during the measurement period. (a) Change of AOD with time;(b) change of cloud with time

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Fig. 13. Total diffuse ratio and AOD at each measurement flight

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Fig. 14. Relative bias of simulated reflectance values for different bands of BRDF models obtained on different days. (a) (b) Model bias on July 28th and July 30th before and after diffuse light correction; (c) (d) model bias on July 29th and July 30th before and after diffuse light correction

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Fig. 15. Spatial distribution maps of ANIF at the 555 nm, 858 nm, and 1240 nm bands after diffuse light correction

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Table 1. Observation data of the airborne BRDF measurement system

Table 1. Observation data of the airborne BRDF measurement system

Date	Time	Solar zenith /（°）	Solar azimuth /（°）
2021-07-28	9：50	42.85	105.82
	11：00	31.97	122.05
	13：00	20.72	183.33
	14：40	30.90	235.73
	15：40	43.50	254.92
	16：40	53.43	264.88
2021-07-29	9：20	49.34	99.32
	10：40	36.09	1115.39
	13：00	20.93	179.45
	14：40	30.53	234.24
	15：40	42.03	252.74
	16：50	54.83	265.77
2021-07-30	9：20	50.26	98.82
	10：40	36.91	114.74
	13：00	21.17	178.95
	14：40	29.32	230.76
	15：40	41.81	252.00

Table 2. Wavelength shifts at different wavelengths
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Table 2. Wavelength shifts at different wavelengths
Sensor Spectral range /nm Wavelength shift /nm
512-element Silicon Linear 350-1000 1
Enhanced 256-element Linear Array 1000-1900 -5
Enhanced 256-element Linear Array 1900-2500 0

Table 3. BRDF model coefficients for fitting three-day data

Table 3. BRDF model coefficients for fitting three-day data

Band /nm	2021-07-28				2021-07-29				2021-07-30
Band /nm	$f_{i s o}$	$f_{v o l}$	$f_{g e o}$		$f_{i s o}$	$f_{v o l}$	$f_{g e o}$		$f_{i s o}$	$f_{v o l}$	$f_{g e o}$
469	0.082	0.085	-0.011		0.094	0.063	-0.002		0.094	0.051	-0.001
555	0.154	0.148	-0.021		0.172	0.097	-0.002		0.171	0.085	-0.002
645	0.228	0.209	-0.030		0.257	0.119	-0.005		0.260	0.095	0
858	0.281	0.236	-0.033		0.312	0.125	-0.004		0.316	0.108	-0.002
1240	0.355	0.236	-0.029		0.372	0.145	-0.010		0.380	0.143	-0.007
1640	0.409	0.236	-0.027		0.443	0.116	-0.007		0.437	0.133	-0.003

Table 4. Model coefficients after diffuse light correction

Table 4. Model coefficients after diffuse light correction

Band /nm	2021-07-28				2021-07-29				2021-07-30
Band /nm	$f_{i s o}$	$f_{v o l}$	$f_{g e o}$		$f_{i s o}$	$f_{v o l}$	$f_{i s o}$		$f_{i s o}$	$f_{v o l}$	$f_{i s o}$
469	0.084	0.131	-0.022		0.089	0.101	-0.016		0.091	0.083	-0.011
555	0.151	0.217	-0.040		0.156	0.174	-0.032		0.165	0.135	-0.018
645	0.233	0.280	-0.051		0.241	0.239	-0.042		0.245	0.187	-0.031
858	0.293	0.354	-0.062		0.303	0.274	-0.050		0.307	0.226	-0.037
1240	0.359	0.379	-0.069		0.371	0.289	-0.053		0.371	0.274	-0.041
1640	0.426	0.249	-0.037		0.426	0.283	-0.051		0.426	0.249	-0.038

Table 5. Statistical analysis of the relative bias and standard deviation of simulated reflectance values for different bands of BRDF models obtained on different days

Table 5. Statistical analysis of the relative bias and standard deviation of simulated reflectance values for different bands of BRDF models obtained on different days

Band /nm	Diffuse-correction between July 30th & July 28th（no-correction）			Diffuse-correction between July 30th & July 29th（no-correction）
Band /nm	Average relative bias /%	STD of relative bias /%		Average relative bias /%	STD of relative bias /%
469	3.953（8.135）	2.288（4.180）		1.528（4.493）	0.807（2.241）
555	4.509（5.877）	2.626（3.595）		2.632（4.304）	1.418（2.442）
645	2.496（7.691）	1.323（4.318）		1.196（5.088）	0.777（2.861）
858	2.456（6.787）	1.306（3.773）		1.161（4.736）	0.788（2.647）
1240	2.038（4.031）	1.212（2.067）		1.271（2.933）	0.885（1.628）
1640	2.183（4.030）	1.268（2.084）		1.144（2.822）	0.900（1.555）

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Yuqing He, Wenjie Hu, Xiuqing Hu, Jibiao Zhu, Xingwei He, Weiqi Jin. Calibration Site BRDF Modeling Method Based on Ground and Low-Altitude UAV Joint Observation[J]. Acta Optica Sinica, 2023, 43(15): 1528001

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Paper Information

Category: Remote Sensing and Sensors

Received: May. 8, 2023

Accepted: Jul. 12, 2023

Published Online: Aug. 15, 2023

The Author Email: Yuqing He (yuqinghe@bit.edu.cn), Wenjie Hu (huwenjiebit@163.com), Xiuqing Hu (huxq@cma.gov.cn)

DOI:10.3788/AOS230941

Topics

laser devices and laser physics

Lasers and Laser Optics

laser manufacturing

Instrumentation, Measurement and Metrology