How is Level-2 HIGHGLINT flag computed?

Hi, could anyone explain how the HIGHGLINT flag is computed? Is it only using viewing geometry and ancillary wind data, or is there also some band reflectance threshold involved?

A lot of the pixels in my Level-2 image are flagged as HIGHGLINT but I have a suspicion/hope that this is by mistake. That entire half of the scene is high glint risk, but only some parts of a small area containing very bright water is actually flagged as HIGHGLINT.

I’ve been looking for information on where this flag comes from and found some info in the OLCI Glint correction ATBD ( and the MERIS handbook ( The OLCI glint correction seems to model a glint spectrum and compare reflectance at 885 nm with the TOA spectrum, and flag the spectrum if reflectance is significantly smaller. But the MERIS algorithm the ATBD refers to uses another threshold based on look-up-tables?
I’m wondering which of these flag threshold is currently used and if either of them are sensitive to very bright water.

I’ve also noticed that the CLOUDMARGIN mask often follows the coastline, maybe this is accidental flagging due to adjacency effect?