Consistency analysis between Sentinel-3A synergy products and PROBA-V Carolien Toté (VITO)

PROBA-V QWG#7 | 3-4 May 2018 | ACRI Context

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SPOT-VEGETATION 1 SPOT-VEGETATION 2 PROBA-V

SENTINEL-3A SENTINEL-3B SENTINEL-3C SENTINEL-3D

S3 SYNERGY products “1km VGT-likes” • VGP: segments (TOA) • VG1: daily composites (TOC) • V10: 10-daily composites (TOC)

remotesensing.vito.be L2 L2 L2

L1C L1B L1B

Hybrid processing chain based on combination of SLSTR and OLCI remotesensing.vito.be Objective

• Preliminary evaluation of the consistency between Sentinel-3 SYN VGT products and PROBA-V Level 2 • Direct comparison over a limited number of segments (TOA)

remotesensing.vito.be Data used

• S3A_SY_2_VGP of last reprocessing (PB 2.26) • Corresponding PROBA-V Level2A segment (Collection 1) • In all 3 cases overlap with RIGHT camera (tilted westwards)

Sentinel-3 PROBA-V Reprocessed SYN data Collection 1, Level 2A Segment (IPF baseline 2.26, dd. Dec/2017) Oceania S3A_SY_2_VGP____20161102T004347_20161102T012804_20171209T0247 PROBAV_L2A_20161102_012206_3_1KM_V102 02_2657_010_259______LR1_R_NT_002.SEN3

Update S3A_SY_2_VGP____20161101T061709_20161101T065709_20180418T1409 dd. 18/04/2018 18_2399_010_248______LR1_D_NT_001.SEN3 Asia S3A_SY_2_VGP____20161101T061252_20161101T065709_20171209T0231 PROBAV_L2A_20161101_062727_3_1KM_V102 46_2657_010_248______LR1_R_NT_002.SEN3

North America S3A_SY_2_VGP____20161107T170417_20161107T174834_20171211T2352 PROBAV_L2A_20161107_174339_3_1KM_V102 19_2657_010_340______LR1_R_NT_002.SEN3 remotesensing.vito.be Esperance, Karakum Desert, New Mexico, South West Australia Turkmenistan USA

PROBA-V S3A PROBA-V S3A PROBA-V S3A

02/11/2016 01/11/2016 07/11/2016 Methods (1/2)

• ‘image stacks’ of S3A_SY_2_VGP and PROBAV L2A • Status map • PROBA-V L2A: exclude pixels labeled as cloud, snow/ice or water, or with bad radiometric quality or bad coverage in one of the spectral bands • S3A_SY_2_VGP: large areas with “SM.ice_or_snow = true”  not used to exclude pixels from the analysis

remotesensing.vito.be Methods (2/2)

• Geometric Mean Regression (GMR)  intercept, slope, R² • Root Mean Squared Distance

푛 1 푅푀푆퐷 = (푋 − 푌 )2 푛 푖 푖 푖=1 • Systematic difference

푅푀푃퐷푠 = 푀푆퐷 − 푀푃퐷푢 • Unsystematic difference

푛 1 푅푀푃퐷 = 푀푃퐷 = 푋 − 푋 푌 − 푌 푢 푢 푛 푖 푖 푖 푖 푖=1 • Mean Bias Error 푛 1 푀퐵퐸 = (푋 − 푌 ) = 푋 − 푌 푛 푖 푖 푖=1

remotesensing.vito.be Results – Visual checks

• Large areas labeled as ‘NaN’ in S3A_SY_2_VGP spectral bands • Inland waters • Clouds / Snow / Bright targets • SM shows ‘ice_or_snow’ for most pixels

remotesensing.vito.be Results – GMR

remotesensing.vito.be Results – GMR

GMR GMR Segment R² MBE RMSD RMPDs RMPDu N intercept slope

Blue Oceania 0.069 0.640 0.49 -0.018 0.024 0.020 0.013 1178400

Asia 0.038 0.962 0.70 -0.030 0.034 0.030 0.015 445455

N. America -0.019 0.983 0.54 0.023 0.054 0.023 0.049 188031

Red Oceania 0.023 0.884 0.61 -0.003 0.030 0.006 0.029 1179641

Asia 0.041 0.880 0.81 -0.012 0.023 0.014 0.019 447065

N. America -0.015 0.997 0.65 0.016 0.045 0.016 0.042 187386

NIR Oceania 0.047 0.886 0.45 -0.021 0.043 0.022 0.037 1184469

Asia 0.044 0.944 0.75 -0.030 0.037 0.030 0.022 447843

N. America -0.005 1.006 0.49 0.004 0.050 0.004 0.050 188636

SWIR Oceania 0.067 1.599 0.48 -0.159 0.167 0.161 0.043 1176405

Asia 0.082 1.476 0.70 -0.167 0.171 0.168 0.029 480847

N. America 0.071 1.394 0.59 -0.129 0.138 0.131 remotesensing.vito.be0.044 191564 Conclusions

• Blue, Red, NIR: relatively high correspondence • RMPDs <3% • RMPDu ~5% (undetected clouds or snow; different illumination conditions related to different overpass times 10:00 a.m. for S3A vs. 10:41 a.m. for PROBA-V)

remotesensing.vito.be 10:50

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9:20 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 time (yy)

remotesensing.vito.be Conclusions

• Blue, Red, NIR: relatively high correspondence • RMPDs <3% • RMPDu ~5% (undetected clouds or snow; different illumination conditions related to different overpass times 10:00 a.m. for S3A vs. 10:41 a.m. for PROBA-V) • Large systematic differences for SWIR • PROBA-V L2A systematically higher than S3A_SY_2_VGP (+13% to +17%) • Related to calibration issues of SLSTR (S5-S6)

cfr. Etxaluze & Smith S3VT, March 2018

remotesensing.vito.be First tests on data with updated SWIR

Oceania segment

GMR GMR R² MBE RMSD RMPDs RMPDu N intercept slope

Before 0.067 1.599 0.48 -0.159 0.167 0.161 0.043 1176405 Update Update 0.070 1.260 0.49 -0.120 0.130 0.121 0.048 1178406

Bias remains large (+17%  +13%)

remotesensing.vito.be Conclusions

• Blue, Red, NIR: relatively high correspondence • RMPDs <3% • RMPDu ~5% (undetected clouds or snow; different illumination conditions related to different overpass times 10:00 a.m. for S3A vs. 10:41 a.m. for PROBA-V) • Large systematic differences for SWIR • PROBA-V L2A systematically higher than S3A_SY_2_VGP (+13% to +17%) • Related to calibration issues of SLSTR (S5-S6) • Issues with SYN status map, artefacts • Future work • Expand analysis on SYN with updated SWIR calibration when new data available • Expand direct comparison in space/time, include VG1 and V10 • Time series analysis

remotesensing.vito.be [email protected] THANK YOU

remotesensing.vito.be