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Several different projections are used for globular
representatons of the earth, orthographic, stereographic, and gnomic.
In all three the lines of both the meridians and parallels may be
curved. On this page the first three stamps show an "equatorial"
projection, while the Cuban stamp is an "oblique" projection.
These are perspective projections which show the earth
as though from a distant point in space. In general, they are neither
conformal nor equal area.
The Australian stamp was
issued in 1981 to mark the 50th annivesary of the first official air
mail in Australia in 1931.
The Chilean stamp was
issued in 1992 to mark the 500th anniversary of the discovery of the
Western Hemisphere.
In 1961 Cuba issued the
stamp to mark the 10th anniversary of Cuban International Broadcast
Service.
The 75th anniversary of
the Universal Postal Union was recognized by Great Britain's issue of
this stamp.
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