MODIS MxD11A2 8-day LST composite QC_Day/Night bands are masked in GEE
Posted: Sun Sep 18, 2022 3:34 pm America/New_York
Hi,
While working on MODIS (MxD11A2.061) 8-day LST and emissivity data in Google Earth Engine, out of curiosity, out team wanted to compare GEE product with AppEEARS product. So, 2021 January's scenes were downloaded from AppEEARS and decoded with ArcGIS MODIS-VIIRS Python Toolbox, and unwanted pixels filtered accordingly. During comparison, we realized that GEE products were having more masked pixels on land than data downloaded using AppEEARS. That led to checking quality band (QC_Day/Night) provided in GEE and these bands were found with large amount of missing pixels on land regions with labelled as "masked" - please see the screenshot of QC_Day band (Terra) on some parts of SE Asia. Checking different years' QC bands, including 2001 (for Terra), the masked pixels were found in all years. Please note, the QC bands of daily LST and emissivity product (MxD11A1.061) do not have such masked pixels.
What are these masked area mean? These masked areas have LST values in "LST_Day(Night)_1km" band; what is the quality of these particular pixels located at the masked areas?
The question was posted in gis.stackexchange and GEE Developers google group, but yet to receive any response. Meanwhile, GEE team confirmed that the issue is not on GEE's end.
Here is the link to GEE script: https://code.earthengine.google.com/91dbffc0cf680291abd3ede8264c022c
Many Thanks,
Salit
While working on MODIS (MxD11A2.061) 8-day LST and emissivity data in Google Earth Engine, out of curiosity, out team wanted to compare GEE product with AppEEARS product. So, 2021 January's scenes were downloaded from AppEEARS and decoded with ArcGIS MODIS-VIIRS Python Toolbox, and unwanted pixels filtered accordingly. During comparison, we realized that GEE products were having more masked pixels on land than data downloaded using AppEEARS. That led to checking quality band (QC_Day/Night) provided in GEE and these bands were found with large amount of missing pixels on land regions with labelled as "masked" - please see the screenshot of QC_Day band (Terra) on some parts of SE Asia. Checking different years' QC bands, including 2001 (for Terra), the masked pixels were found in all years. Please note, the QC bands of daily LST and emissivity product (MxD11A1.061) do not have such masked pixels.
What are these masked area mean? These masked areas have LST values in "LST_Day(Night)_1km" band; what is the quality of these particular pixels located at the masked areas?
The question was posted in gis.stackexchange and GEE Developers google group, but yet to receive any response. Meanwhile, GEE team confirmed that the issue is not on GEE's end.
Here is the link to GEE script: https://code.earthengine.google.com/91dbffc0cf680291abd3ede8264c022c
Many Thanks,
Salit