RIVM report xxxxxx xxx

page 114 of 142 RIVM report 773301 001 / NRP report 410200 051
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for all intermediate cells, i.e. grid cells with a population density between the urban and rural cut-off
values, we ranked the grid cells per country in order of decreasing population density and applied an
algorithm for allocating fractions of urban/rural population per grid cell in such a way that the
national urban and rural population fractions were equal to the fractions published in the 1990
population statistics of the UN (1999).
The resulting maps have been compared with high-resolution urban and rural population maps for China,
where urban population was based on a cut-off density per high-resolution grid cell. Both visual
inspection of the spatial pattern as well as the shape of the urban and rural population density
distributions (number of grid cells ranked according to decreasing densities) showed good agreement.
The results of this algorithm are shown in )LJXUHV$ and $, where we show the urban and rural
maps, respectively, using the same classification as in the total population map of )LJXUH $. Visual
inspection clearly shows that the urban map is not extending in thin populated areas in larger countries
such as the northern part of Canada, mid-west of the USA, remote areas of the Russian Federation,
western and north-eastern parts of China, and mid Australia.