How it works
The level-3 products from SeaWiFS, MODIS and their successors are stored on a grid from
NASA Technical Memorandum 104566, volume 32 (Campbell, Blaisdell and Darzi, 1995), described for
today's files in the L3 bin
format notes. The globe is cut into rows of
equal height. Each row holds a whole number of bins, as many as fit round its middle latitude at the
width of the bins at the equator, so every bin has nearly the same area.
Unwrap shows it in three moves: the globe swells to a cylinder, the cylinder opens with each row
shrunk to its own width (an integerized sinusoidal projection, stepped where the bin count changes),
and the rows slide left into the ragged array the bins are stored in, numbered from 1 in the south-west
corner, west to east, south to north.
Click anywhere for the bin under the pointer, or type a bin number, or a longitude and latitude.