In GPWv3, how do you consider the population density in a bin (0.25 deg x 0.25 deg) when it is partly landmass and partly water (e.g., sea, ocean)? Do you evaluate the density as the total number of humans over the total surface of this bin (so, approximately, let's say 30 km x 30 km, even if depending on latitude) or just only over the landmass part?

The land area of a given grid cell is computed by finding the surface area, then subtracting water areas. Population is then allocated on the basis of the land area, which is in most cases less than the surface area of the cell.  We account for areal differences by latitude as well.

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