Glint correction for the DSF

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A glint correction for the DSF was added in ACOLITE 20180917.0

The DSF estimates the path reflectance by using the band giving the lowest aerosol optical thickness, hence the use of pixels and bands with severe sun glint is avoided in the aerosol correction. This allows for a separate estimation of sun glint from bands with no expected signal originating from below the water surface (e.g. using the SWIR, as done by Harmel et al., 2018).

The glint correction can be applied to any of the supported sensors (L5/TM, L7/ETM, L8/OLI, S2A/MSI and S2B/MSI), and has to be activated in a settings file, by setting glint_correction=True. The performance of the correction depends on the sensor signal-to-noise ratio and the severity of the glint. Further options are briefly discussed in the user manual.

In the posts below the application of the glint correction is illustrated using imagery of the Mississippi River plume (limit=28.60,-89.80,29.20,-88.75), using a surface reflectance RGB composite and a turbidity product derived from the red band. In the Landsat examples the default masking threshold was increased to 0.05 (l2w_mask_threshold=0.05). The S2A images were merged and processed at 60 m using a masking threshold of 0.08.

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L5/TM image of 2009-06-07 (LT05_L1TP_021040_20090607_20160906_01_T1)

(1) rhos RGB without glint correction

L5_TM_2009_06_07_16_14_29_021040_rgb_rhos_noGC.png (257.31 KiB) Viewed 7192 times

(2) rhos RGB with glint correction

L5_TM_2009_06_07_16_14_29_021040_rgb_rhos_GC.png (239.39 KiB) Viewed 7192 times

(1) t_nechad without glint correction

L5_TM_2009_06_07_16_14_29_021040_t_nechad_noGC.png (294.15 KiB) Viewed 7192 times

(2) t_nechad with glint correction

L5_TM_2009_06_07_16_14_29_021040_t_nechad_GC.png (296.25 KiB) Viewed 7192 times

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L8/OLI image of 2018-04-29 (LC08_L1TP_021040_20180429_20180502_01_T1)

(1) rhos RGB without glint correction

L8_OLI_2018_04_29_16_25_30_021040_rgb_rhos_noGC.png (193.18 KiB) Viewed 7191 times

(2) rhos RGB with glint correction

L8_OLI_2018_04_29_16_25_30_021040_rgb_rhos_GC.png (179.03 KiB) Viewed 7191 times

(1) t_nechad without glint correction

L8_OLI_2018_04_29_16_25_30_021040_t_nechad_noGC.png (211.82 KiB) Viewed 7191 times

(2) t_nechad with glint correction

L8_OLI_2018_04_29_16_25_30_021040_t_nechad_GC.png (214.72 KiB) Viewed 7191 times

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S2A/MSI image of 2017-07-27 (tiles S2A_MSIL1C_20170727T162901_N0205_R083_T16RBT_20170727T164340.SAFE
S2A_MSIL1C_20170727T162901_N0205_R083_T16RCT_20170727T164340.SAFE
S2A_MSIL1C_20170727T162901_N0205_R083_T16RCS_20170727T164340.SAFE
S2A_MSIL1C_20170727T162901_N0205_R083_T16RBS_20170727T164340.SAFE)

(1) rhos RGB without glint correction

S2A_MSI_2017_07_27_16_29_01_MERGED_rgb_rhos_noGC.png (265.48 KiB) Viewed 7191 times

(2) rhos RGB with glint correction

S2A_MSI_2017_07_27_16_29_01_MERGED_rgb_rhos_GC.png (252.19 KiB) Viewed 7191 times

(1) t_nechad without glint correction

S2A_MSI_2017_07_27_16_29_01_MERGED_t_nechad_noGC.png (292.67 KiB) Viewed 7191 times

(2) t_nechad with glint correction

S2A_MSI_2017_07_27_16_29_01_MERGED_t_nechad_GC.png (304.63 KiB) Viewed 7191 times