A New Oblique Equal-Area Projection

Abstract

OST published equal-area maps of the world show the major land masses with excessive shape distortion in certain areas or with a break in continuity. L VI v Notably, the relationship between Asia and the Americas is usually unsatisfactory, because of a lack of continuity in the Arctic and sub-Arctic regions. This is the case in such frequently used equal-area projections of the world as the Sinusoidal and the normal forms of the Mollweide and Hammer-Aitoff. Oblique forms of these projections, especially with the center at 450 N. and about 100 E., are preferable, because the Arctic Sea is shown without interruption and the land masses usually fall within areas of small shape distortion. The American Geographical Society many years ago started experimenting with the oblique Mollweide so centered, but examples of maps drawn on this projection were not published until World War II.U More recently it occurred to the writer that a somewhat better result would be obtained by utilizing an oblique version of the HammerAitoff. Such a projection was constructed and was used to illustrate H. Duncan Hall's article Zones of the International Frontier in the Geographical Reviewt.2 In both the Mollweide and the Hammer-Aitoff the major axis of the bounding ellipse is twice the length of the minor axis. In the oblique forms of these projections the parallels of latitude close to the North Pole are shown as ovals. It would be more desirable, however, to show these parallels as near circles; this would preserve closely the true relationship between the northern continents. To this end, the writer developed a projection with a bounding ellipse whose major axis is I.75 the minor axis, and constructed it graphically from the Lambert Azimuthal Equal-Area by a procedure similar to that used in constructing the Hammer-Aitoff. Such a map projection is particularly useful for the plotting of world distributions. The projection has been used for several maps in the Society's Atlas of Diseases, on various scales. In response to a number of requests, outline maps on two convenient scales have now been prepared and are available.3