Land Water Mask Difference Image

The image below shows the density of difference between the C5 and C6 version of the Land Water Mask. The purpose of this difference image is to highlight the geographic regions with the highest concentrations of difference between the two versions of the C5 and C6 LWM. The first step in generating the difference image was to re-grid the MODIS C5 water mask from a 1km to a 500m spatial resolution using a nearest neighbor resampling. Next, both the C5 and C6 500m global images were reclassified into binary maps where all the ocean and inland water classes were combined into one class, and all the non-water classes were grouped into the other. Subsequently, the C5 binary map was then subtracted from the C6 binary map to produce the difference map. Using an exact averaging technique the difference map was averaged back up to a 25km resolution, which produced a "percent net difference" per 25km grid cell map. Finally, for ease of visualization the LWM difference map was projected back onto a 500m grid.

The white paper that documents the development of the C6 LWM is available here.

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