This file is the percent water surface coverage file used for the IMERG products. It is on a 0.1°x0.1° grid as REAL*4 (3600,1800). The orientation is the same as the IMERG data. The file displays percent water surface coverage with 100% = all water and 0% = all land.

Land sea is also called land ocean or land water. Typical percentage thresholds used to define sea are 100% (strictly open water) or 75% (including sea-ward coast areas). Typical percentages used to define strictly land are 25% or 15%; too low a percentage masks out humid regions that have many lakes and reservoirs.  Users should inspect the resulting masks to check that they correspond to the expected map.