Cloud Cover Detection with machine learning algorithm and multispectral imaging.
Channel: TWO & Solutions
Date: 2021-03-07

Two science and research group provides cloud cover detection with machine learning algorithm and spaceborne multispectral imaging as following:

$1 Categorizing clouds snow water and clear sky is a significant input for atmospheric correction, as well as precalibration process. The existence of clouds makes it difficult to observe the Earth's surface. This research team presents classification algorithms which are all based on a publicly available database of manually classified Sentinel-2A images. Also those are based on commonly used machine learning techniques such as decision trees, random forests, or support vector machines. 

$2 Algorithm suggested in this study decision tree of depth three to discriminate from Water and Shadow, Clear and Cirrus, Cirrus and Snow, and Cloud and Snow.

$3 to $4 They applied to visible bands with Band 3 and Band 4, near infrared and mid infrared (or shortwave infrared). It is interesting to use Band 4 in Red to distinguish Cirrus from Snow. One of Thermal bands, Band 10, also applied to determine Clear and Cirrus

Question: In this paper, did they apply to Top Of Atmosphere reflectance or Bottom Of Atmosphere reflectance?

Sentinel 1C product provides Top Of Atmosphere (TOA) reflectance while Sentinel 2C product with Bottom Of Atmosphere reflectance. The latter was done with atmospheric correction.

$5 A comparison between RGB True color composite and classification image which showed the potential of a ready-to-use method with machine learning techniques. This method is well detected cloud cover across Sentinel 2 images.

$6 Here is another open source algorithm which originally had developed by Finnish Meteorological Institute (FMI) to describe cloud detection algorithm with AATSR products

BT11 and BT3.7 are thermal bands of AATSR - Brightness temperature
Difference threshold
NDSI is Normalized Difference Snow Index which is the ratio of the difference in Visible and SWIR reflectance.
R0550 is a visible band.
With a set of thresholds to determine the existence of cloud with either mask=1 or mask=2, 

A combination of visible, NDSI, and thermal bands which originally developed by FMI could apply to other multispectral spaceborne products after threshold adjustments. It is because of describing well the uncertainty of Earth surface observation in FMI technical report.

$7 The specification of the Advanced Along-Track Scanning Radiometer (AATSR) Instrument - pixel resolution, radiometric accuracy, and seven spectral channels.

$8 A comparison between AATSR RGB composite image, and the product with cloud mask showing a potential of FMI cloud detection algorithm.

#CloudCoverDetection #DetectionOfClouds #Sentinel2MSI #MachineLearning
 
Reference:
-  260 free vector icons of International flags designed by Freepik https://www.flaticon.com/packs/international-flags-3?k=1615208613470 via @flaticon

- Technical note 2 Cloud Detection Algorithm SCDA - Globsnow Monitoring for Climate Research by Finnish Meteorological institute (FMI), https://www.globsnow.info/docs/GlobSnow_technical_note2_scda_final_release.pdf
- Ready-to-Use Methods for the Detection of Clouds, Cirrus, Snow, Shadow, Water and Clear Sky Pixels in Sentinel-2 MSI Images, Helmholtz-Zentrum Potsdam, https://doi.org/10.3390/rs8080666, Remote Sensing (ISSN 2072-4292).
- ENVISAT-1 product specifications, aatsr products specifications (ESA Doc Ref: PO-RS-MDA-GS-2009), ESRIN, https://earth.esa.int/eogateway/instruments/aatsr/description
- https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi/resolutions/radiometric

- United Kingdom free vector icons designed by Freepik https://www.flaticon.com/free-icon/united-kingdom_299688?term=uk%20flag via @flaticon (on twitter)
- France free vector icons designed by Freepik https://www.flaticon.com/free-icon/france_299753?related_id=299753 via @flaticon (on twitter)


➤ Computer and hardware used:
- My laptop: https://amzn.to/3iStQD5
- Monitor: https://amzn.to/3iMx1fu
- Display Port (DP) to HDMI Cable: https://amzn.to/36VHDGE
- Pin microphone: https://amzn.to/3di11ig

DISCLAIMER: Links included in this description might be amazon affiliate links. If you purchase a product with the links as above, I may receive a small amount of commission. There is no additional charge to you for sure!

@ 2021 by TWO & Solutions. All rights are reserved.