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The GRASS engine used in AccessMod will resample raster format layers presenting a different resolution than the DEM to make it match the DEM’s resolution.

The resampling technique used by the GRASS engine is the similar to a "nearest neighbor" one . This technique assigns (i.e.. assigning the value in each "new" pixel based on the value stored in the nearest "previous" pixel). However, GRASS is not using a dedicated "nearest neighbor" function in that case, but rather applies a "pixel mask" of the resolution of the DEM over any other raster, and assign the values of the other raster to match the resolution of the DEM. While using such technique might be appropriate when applied to the landcover raster format layer We were not able to specify exactly how GRASS proceeds to do that, so we should not assume the process is a clean "nearest neighbor" attribution. It is therefore strongly encouraged to always ensure that the input raster files have the exact same resolution.

While change of raster resolution may likely be correct for categorical raster such as the the landcover, this is not the case for the population distribution layer as this transformation will not conserve the original total population and can therefore translate in wrong output statistics.