Spatiotemporal reflectance blending in a wetland environment

Figures & data

Figure 1. Study area of Poyang Lake National Nature Reserve (PLNR), China.

Table 1. Acquisition dates of the input Landsat-5 TM and Terra MODIS images for the customized model.

			MODIS
Year	Code	TM	Prior	Posterior
2004	A, a	24 July	22 July	27 July
	B, b	28 October	27 October	29 October
	C, c	29 November	28 November	2 December
	D, d	15 December	12 December	16 December
2005	E, e	5 March	22 February	6 March
	F, f	12 August	8 August	17 August
	G, g	13 September	12 September	16 September
	H, h	29 September	21 September	30 September
	I, i	31 October	30 October	21 November

Figure 2. Flowchart of customized blending model based on ESTARFM. t_t refers to target date of blended reflectance image, t_m and t_n refers to acquisition dates of prior and posterior TM images, t_m − and t_m + refers to acquisition dates of prior and posterior MODIS images for prior TM image, and t_n − and t_n + refers to acquisition dates of prior and posterior MODIS images for posterior TM image.

Figure 3. False color images of observed and blended reflectance: observed TM reflectance (a and d); blended reflectance predicted by customized model (b and e); and blended reflectance from ESTARFM for 28 October 2004 (c and f). Green, red, and near infrared (NIR) bands were assigned to blue, green, and red in images along top row (a–c), and blue, shorter portion of shortwave infrared (S-SWIR), and longer portion of shortwave infrared (L-SWIR) bands were assigned to blue, green, and red in images along bottom row (d–f).

Table 2. AAD and AD between observed reflectance and blended reflectance from the customized model and ESTARFM for 28 October 2004.

	AAD, %reflectance		AD, %reflectance
Band	Customized model	ESTARFM	Customized model	ESTARFM
Blue	0.92	1.08	0.04	0.05
Green	1.50	1.75	0.85	0.30
Red	1.55	1.65	0.41	0.54
NIR	3.52	3.78	−0.84	−0.49
S-SWIR	3.65	4.37	0.08	1.27
L-SWIR	3.00	3.26	−0.10	0.87

Table 3. Adjusted correlation coefficient (adjusted R ² ) between factors in input images and AAD between observed and blended reflectance.

	Band
Season	Blue	Green	Red	NIR	S-SWIR	L-SWIR
Shorter image observation interval
All	0.02	0.00	0.10	0.12	0.33	0.38
Spring	0.08	0.00	0.35	0.43	0.27	0.23
Summer	0.00	0.01	0.61	0.55	0.51	0.19
Fall	0.02	0.00	0.10	0.18	0.20	0.22
Winter	0.64	0.26	0.56	0.71	0.81	0.87
Smaller absolute water level difference between prior or posterior dates and target dates
All	0.16	0.14	0.40	0.53	0.64	0.61
Spring	0.46	0.34	0.24	0.19	0.34	0.37
Summer	0.62	0.00	0.00	0.38	0.66	0.67
Fall	0.23	0.30	0.54	0.73	0.58	0.51
Winter	0.69	0.41	0.77	0.94	0.92	0.94

Figure 4. Relationship of the mean values of AAD between observed and blended spectra in all bands with smaller absolute difference of water level between prior or posterior dates and target dates.

Table 4. Agreement between observed and blended reflectance with combination of input image sets achieving smallest mean values of AAD for all spectral bands: (a) AAD, (b) AD.

(a)
Target date				AAD,% reflectance
Year	Date	Combination	Area	Blue	Green	Red	NIR	S-SWIR	L-SWIR	Mean: all
2004	28 October	aBc	Whole	0.92	1.50	1.55	3.52	3.65	3.00	2.36
			Land	0.86	1.48	1.42	4.16	4.14	3.31	2.56
			Water	1.04	1.56	1.83	2.27	2.69	2.40	1.96
	29 November	bCd	Whole	0.90	1.30	1.36	2.11	2.79	2.25	1.78
	15 December	cDh	Whole	1.39	1.52	1.58	2.25	3.37	2.86	2.16
2005	5 March	dEg	Whole	2.33	2.15	1.88	3.48	4.26	3.51	2.94
	12 August	aFg	Whole	2.82	3.09	2.51	5.26	2.94	1.76	3.06
	13 September	fGh	Whole	3.65	3.65	2.98	5.36	3.84	2.56	3.67
	29 September	aHi	Whole	1.60	1.56	2.23	4.09	3.17	2.90	2.59
(b)
Target date		AD,% reflectance
Year	Date	Area	Blue	Green	Red	NIR	S-SWIR	L-SWIR
2004	28 October	Whole	0.04	0.85	0.41	−0.84	0.08	−0.10
		Land	−0.08	0.78	0.30	−1.65	−0.24	−0.30
		Water	0.28	0.99	0.63	0.74	0.71	0.30
	29 November	Whole	0.07	−0.58	−0.16	−0.31	0.05	0.00
	15 December	Whole	−0.81	−0.01	0.17	0.22	−0.74	−1.18
2005	5 March	Whole	2.05	1.26	0.31	−0.66	−0.92	0.06
	12 August	Whole	2.24	2.34	1.45	1.94	0.31	−0.04
	13 September	Whole	3.03	1.55	1.49	1.35	2.30	1.29
	29 September	Whole	0.08	−0.32	0.21	−1.38	0.28	−1.22