A cylindrical projection that is equal-area. Very similar to the Cylindrical Equal Area projection (also known as the Lambert Cylindrical Equal Area projection) but with standard parallels at 45 degrees North and South.
No distortion of scale and shape at the standard parallels of the normal aspect but great distortion of shape and scale otherwise.
Substantial shape and scale distortion near points 90 degrees from central line resulting in vertical exaggeration of Equatorial regions with compression of regions in middle latitudes and extreme vertical aspect compression in higher latitudes. Greater vertical aspect (taller) than the Cylindrical Equal Area projection upon which it is based.
Used mainly for political propaganda intended to maximize the apparent size of nations in Africa. Rarely used in professional cartography due to shape distortion. Usable for practical purposes only near the Equator.
Devised by James Gall in 1855 as a modification of the 1772 projection by Johann Heinrich Lambert.
Propaganda in Action: The "Peters Projection"
While cartographic technology, like many technologies, is of course routinely misused to lie to people for political ends, it is only on comparatively rare occasions through the centuries that political assaults have been launched against specific technologies within cartography itself. Such is the case with the "Peters projection" in modern times, when the twin hydras of political correctness and technical ignorance have combined to enmesh Gall's work within a contemporary propaganda movement. In an ironic twist, the misuse of cartography by this movement was advanced by an attack on the Mercator projection, an evil modern echo of the religious / political attack 450 years ago on Mercator himself.
Despite profound shape distortion and other defects, the Gall projection was adopted by Arno Peters of Germany in 1967, who falsely claimed the invention of the projection as his own. The "Peters projection" is, in fact, identical to the Gall except for an insignificant difference in standard parallels.
A student of political propaganda, Peters continued to claim his "invention" was distinctly different from the Gall projection even after it was conclusively demonstrated by professional cartographers that the so-called "Peters" projection was indeed the Gall. It is thus difficult to believe that Peters independently re-invented this projection as opposed to wilfully plagiarizing the Gall, even if one is so credulous to think that Peters as an avid technical critic of the Mercator and other cylindrical projections could have somehow escaped noticing the vast literature describing the Lambert, the Gall and other similar projections. Like many evident plagiarists, Peters would have us believe that he managed to read the books he researched for "his" work while somehow honestly not noticing those parts he claims as his own.
Even after repudiation of their assertions by professional cartographers, both Peters and his political supporters continued to promote this "invention" through false claims. For example, the projection is claimed to be uniquely equal-area when there are numerous other projections, such as the Lambert Cylindrical Equal Area upon which it is based, that are also equal-area. It is claimed to be free of shape distortion when in fact it highly distorts shapes. It is claimed to preserve scale throughout the projection when in fact scale is true only along the two standard parallels and otherwise highly distorted throughout the projection.
Perhaps most telling of the political objectives of Arno Peters and his followers, the main claim for the projection is that it is more even-handed in presenting the true, relative size of Third World nations than are other projections, in particular the Mercator. But even this claim is false since any equal area projection will show the true areas of all nations, and numerous other projections do a better job of showing a more "realistic" apparent shape and size of different nations, including Third World nations, as they would be seen, say, to a politically-unbiased observer hovering above our planet. But then the very even-handedness of such projections works against them in service of the propaganda missions for which the "Peters" is deployed.
In fact, the Gall projection was apparently adopted by Arno Peters precisely because it distorts the apparent size of nations to overemphasize those nations favored by Arno Peters and his followers. While Peters criticized for apparent distortion the Mercator projection that is widely used for navigation worldwide, he and his followers falsely misrepresented his own use of the Gall projection as being free of distortion.
The Gall (and hence the "Peters" projection) greatly exaggerates the apparent size of equatorial countries through vertical scale exaggeration while compressing regions away from the Equator. It therefore makes First World countries in North America and Europe look smaller in comparison to Africa, which becomes enormous. This is, of course, a useful trick for political propaganda seeking to make Africa look larger and First World countries look smaller.
Note, by the way, that criticism by Peters supporters of the Mercator projection as motivated by political incorrectness is somewhat off the mark for those familiar with the technical characteristics of Mercator's projection and the history of its adoption.
As is well known to cartographers, the Mercator projection's wide adoption had nothing to do with any political agenda to minimize the geographic role of Third World countries. The Mercator won popularity first because it is easy to construct and second (and most importantly) because it shows rhumb lines as straight lines, a characteristic that is extremely useful for navigation. The Mercator is also highly useful for conformal mapping of regions predominantly bordering the Equator, which is one reason it is often used by development and relief organizations wishing to employ effective tools in their assistance to equatorial Third World countries.
Keeping in mind that until the very recent, widespread dispersion of computers the cost of preparing virtually any cartographic presentation was very high, it made sense (especially in poorer countries) to choose a projection that works well for navigation even if the primary purpose of the map was not for navigation. If one can afford to prepare and print only one map it is prudent to create that map so it is well-suited for navigation given the likelihood that even maps prepared for other purposes might end up being pressed into service for navigation. Thus the Mercator has been widely used even in maps not primarily aimed at navigation. Indeed, many voyagers on a budget have used Mercator maps for navigation that were originally created for other purposes.
Far from promoting a thin band of First World latitudes, if anything, the Mercator grossly disfavors such latitudes by overstating the geographic importance of regions populated by Arctic peoples and high latitude indigenous populations. Perhaps what really annoys Peters advocates is that the Mercator overemphasizes the habitat of Third World populations in regions other than those favored by Peters partisans. Even so, to suggest that because the Mercator is bad one should employ the "Peters projection" doesn't hold water given the many projections other than the Mercator which are both readily available and clearly superior to the Gall should equal representation be the goal (which, of course, it is not for Peters partisans, who seek an unequal representation for their side).
From a purely technical perspective, falling for "Peters projection" propaganda does a disservice to Third World nations by applying a projection that denies them the technical benefits of more effective cartographic tools. It is a sad statement of the triumph of politically-motivated publicity that organizations such as UNESCO have adopted the "Peters projection" despite the poor cartographic properties of the projection. While some partisans apologize for the Peters movement by stating that "all maps are political," only someone bereft of technical knowledge could so claim given the many profoundly useful technical characteristics of various projections in matters that have nothing to do with politics. See, for example, the Guide to Selecting Map Projections topic.
While there will always be propagandists eager to employ GIS to deceive, all friends of GIS can fight such deception by patiently working to correct misunderstandings fostered by the popular media and other inexpert information channels. A fair representation of the Earth upon a flat surface is a noble goal, the original reason for projections to have been invented in the first place. It continues to be a goal worth fighting for even when the effort is attacked for political reasons.
Just as Mercator himself continued his work even after the attacks upon him for his own cartographic work, GIS advocates can help push back against political pressure by patiently explaining the technical properties of projections and by providing examples of how modern computer technology can show our world in a fair and neutral way for the benefit of all concerned.