In a statement, the 126-year-old non-governmental scientific institution -- as famous for its cartography as for its yellow-bordered magazine -- said its mapping policy "it to portray, to the best of our ability, current reality."
While most boundaries depicted in its maps and atlases are stable and uncontested, disputed places are liable to be shaded gray as "areas of special status" with a text explanation alongside them.
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"In the case of Crimea, if it is formally annexed by Russia, it would be shaded gray and its administrative center, Simferopol, would be designated by a special symbol," it added.
"When a region is contested, it is our policy to reflect that status in our maps. This does not suggest recognition of the legitimacy of the situation."
In a blog on its website, National Geographic said it has applied the same principle when mapping Abkhazia, South Ossetia, Gaza and the West Bank, and several other disputed territories.
Russia's parliament is to consider Friday whether to absorb Crimea following a disputed referendum Sunday in which 97 percent of Crimeans who participated favored separation from Ukraine.
Ukraine and the West have rejected the referendum as illegal.