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This map image, as it is today, is a horror. It cuts off western Europe at the top splits and distorts western Europe beyond recognition.
Compare this map image with all other renderings of Guyou's Doubly-Periodic Projection (web search). Whether with continent outlines or colored continents and oceans, they do not share this problem. Examples:
(Some of these are public domain or CC.)
Guyou's Doubly-Periodic Projection uses heavy distortion. It actually does not make a complete world map. It distorts some regions beyond recognition due to singularities, the bane of conformal projections. Across the vertical centerline is a span where everything north of 50°N or south of 50°S is projected right out of the rectangle shrunk, twisted, and even inverted. Guyou's Doubly-Periodic Projection puts much ocean area across the centerline, but no one notices that four "featureless" ocean areas are missing distorted beyond recognition.
This map image uses the same distortion as the original. (That is not immediately obvious, because this map has 15° line spacing and the distortion map has 10° line spacing.) This map image puts the equator (0°N) on the horizontal centerline, also the same.
The difference is: This map image is centered on the Prime Meridian (0°E), which puts western Europe across the centerline, making it disappear, distorting it beyond recognition, which is a deal breaker. The original map is always centered on 20°W longitude.
This map image nicely keeps New Zealand with Australia and doesn't break up Siberia as badly, but scrambling western Europe is not worth it. (In the actual Guyou's Doubly-Periodic Projection, people in Australia, Pacific islands, and Pacific Rim could swap the left and right halves, yielding a map centered at 160°E, which is also a very nice view.) - A876 ( talk) 19:50, 14 February 2022 (UTC)
See, that wasn't so hard. (kidding) Yeah I guess it was harder than it had to be. Going forward, I'll try to be more considerate, though it takes additional rewrite before posting to recast my objections with less-brutal honesty. I didn't encounter any Guyou or variant that didn't choose a meridian offset to avoid putting land-area in a singularity, except maybe as counterexamples. (I know I'm limited to what's online. One nice set I only found by accident; an image on Pinterest and Tumblr linked to a vanished website now available only via Internet Archive.) The primality of the Prime Meridian isn't absolute; there have been several over the centuries, though 0° longitude is a familiar line. Some projections cannot tolerate adding a meridian offset; for example, the Goode homolosine projection would become gruesome, with rifts splitting continents instead of oceans. I think the Guyou has to be treated the same way. - A876 ( talk) 06:06, 18 February 2022 (UTC)
![]() | This file does not require a rating on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||
|
This map image, as it is today, is a horror. It cuts off western Europe at the top splits and distorts western Europe beyond recognition.
Compare this map image with all other renderings of Guyou's Doubly-Periodic Projection (web search). Whether with continent outlines or colored continents and oceans, they do not share this problem. Examples:
(Some of these are public domain or CC.)
Guyou's Doubly-Periodic Projection uses heavy distortion. It actually does not make a complete world map. It distorts some regions beyond recognition due to singularities, the bane of conformal projections. Across the vertical centerline is a span where everything north of 50°N or south of 50°S is projected right out of the rectangle shrunk, twisted, and even inverted. Guyou's Doubly-Periodic Projection puts much ocean area across the centerline, but no one notices that four "featureless" ocean areas are missing distorted beyond recognition.
This map image uses the same distortion as the original. (That is not immediately obvious, because this map has 15° line spacing and the distortion map has 10° line spacing.) This map image puts the equator (0°N) on the horizontal centerline, also the same.
The difference is: This map image is centered on the Prime Meridian (0°E), which puts western Europe across the centerline, making it disappear, distorting it beyond recognition, which is a deal breaker. The original map is always centered on 20°W longitude.
This map image nicely keeps New Zealand with Australia and doesn't break up Siberia as badly, but scrambling western Europe is not worth it. (In the actual Guyou's Doubly-Periodic Projection, people in Australia, Pacific islands, and Pacific Rim could swap the left and right halves, yielding a map centered at 160°E, which is also a very nice view.) - A876 ( talk) 19:50, 14 February 2022 (UTC)
See, that wasn't so hard. (kidding) Yeah I guess it was harder than it had to be. Going forward, I'll try to be more considerate, though it takes additional rewrite before posting to recast my objections with less-brutal honesty. I didn't encounter any Guyou or variant that didn't choose a meridian offset to avoid putting land-area in a singularity, except maybe as counterexamples. (I know I'm limited to what's online. One nice set I only found by accident; an image on Pinterest and Tumblr linked to a vanished website now available only via Internet Archive.) The primality of the Prime Meridian isn't absolute; there have been several over the centuries, though 0° longitude is a familiar line. Some projections cannot tolerate adding a meridian offset; for example, the Goode homolosine projection would become gruesome, with rifts splitting continents instead of oceans. I think the Guyou has to be treated the same way. - A876 ( talk) 06:06, 18 February 2022 (UTC)