This
level-4 vital article is rated B-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||||||||||||
|
Map projection was one of the Geography and places good articles, but it has been removed from the list. There are suggestions below for improving the article to meet the good article criteria. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake. | |||||||||||||
| |||||||||||||
Current status: Delisted good article |
Shouldn't there be somewhere on this page an indication of which projection to use to make a planetary texture to be used on a sphere ? The first place one searches for such a clue is there... I can't write it down for now, because I haven't found it yet, and moreover I don't know editing rules in Wikipedia, so should I write something that I would surely break many of them ^-^ It seems to be called "square" or "rectangular" on many planet generators, but I don't know the proper geographical term and I thought to find it here. That's why I think it would be useful here. Thanks in advance !
Benoît 'Mutos' ROBIN — Preceding unsigned comment added by 77.193.41.178 ( talk) 16:10, 13 November 2011 (UTC)
The images showing examples of projections seem out of place; the images don't relate to the text next to which they are placed. It seems the images placed merely for overall appearance of the article, however this is not very conducive to understanding. —Preceding unsigned comment added by 134.197.40.199 ( talk) 19:43, 15 June 2009 (UTC)
I am not sure whether I am right on this one, but these images seem identical with ESRI's poster on map projections that comes with their book "Getting to know ArcGIS". Someone should verify the copyright of these images. The USGS website does not mention any copyright information.
I don't know if the articles for projections exist, but it might be worth nabbing those that do from Planet math. Mr. Jones 15:05, 8 May 2004 (UTC)
You should put a ":" before the math marker of the Mercator formula, to indent it. Same with the next line starting with phi. – Martin Vermeer
12/29/05
It would be a good idea to add a short section on the history of Map Projections - this is an interesting topic, as it mirrors the evolution of human knowledge over the centuries. Great ingenuity has gone into developing the ideas of map projection to make it more and more useful for navigators and other users.
I have invented a superior map. Everyone will agree that it is the best. How do I submit it? 70.177.90.238 20:40, 11 January 2006 (UTC)
IMHO spherical projection is the more standard mathematical term for this. i've done a redirect from spherical projection to this article, but if noone objects, then i would suggest switching the redirect to the other direction - i.e. "spherical projection" would be the main article. Boud 08:41, 27 April 2006 (UTC)
The article uses maps with America at the centre. I though that the Wikipedia standard was to use maps with Europe/Africa at the centre (because they don't cut Asia in half). If so, does this article deviate from that for a specific reason? And are there names for these maps (I can't find an article on it)? DirkvdM 07:06, 17 August 2006 (UTC)
A while back I heard of a type of projection that was made up of a bunch of triangles, and that by unfolding it a certain way, it showed the world as a chain of continents surrounded by water, or a chain of oceans surrounded by land. Does anyone have any information on this? Stale Fries 00:13, 3 March 2007 (UTC)
I think placing the Dymaxion Map under the heading "compromise projections" is missleading as it is the only unique map among those listed and the description for the section in no way describes the Dymaxion Map. I think part of the confusion above stems from the poor classification of this map. 71.214.83.247 ( talk) 05:46, 3 January 2008 (UTC)
The statement that cylindrical projections have straight meridians is true only for the conventional (projection axis == earth axis) form, not for the transverse or oblique forms. Paul Koning 17:50, 10 May 2007 (UTC)
... whereas most maps show only a small part of the earth. I realize that this is just "a special case" where you only show part of the map, but given the extremely common nature of this issue there should be some specific discussion of what projections are commonly used for smaller maps (and how to choose the parameters). Personally, I'm trying to figure out which projection to use for my map of a country (Guatemala) but the same issue exists even for the smallest, city-scale maps. -- 190.56.85.26 17:10, 11 July 2007 (UTC)
Just found [3] which is much more "useful" from my perspective than this article, as it organizes by purpose rather than by mathematical criteria. I would suggest that this article should keep the initial explanations as is, but the actual projections should be reorganized along the lines of this source.
ps. For my purposes, I've chosen LCC - appropriate for a "taller" country and atlas-style "just looking" maps. Now, I just have to figure out how to enter the parameters into GRASS - it asks for "central", "first", and "second" parallels, which default to 23,33,and 45; I try 15,13,and 17 for a map which will extend 13N to 18N and it doesn't accept them... maybe I need to use negative rather than positive numbers for my false northing and false easting...
pps. Sure it makes hardly any difference for city maps - but you still have to choose one. -- 190.56.85.26 18:48, 11 July 2007 (UTC)
Many articles on projections, such as equirectangular projection, use some kind of "modern notation" in favor of a more understandable x = x(λ, φ), y = y(λ, φ) type of thing that would be easier to understand and is more standard in terms of notation.
This is a notation occasionally used for functions/mappings, but it may not be the best choice here, the shorthand really doesn't make it shorter and only obscures it.
If no one objects I'm intent on fixing all map projection articles that use this convention.
Edit: sorry, forgot to sign. - Ben pcc 22:43, 27 July 2007 (UTC)
I favor this proposal. The so-called "modern notation" is not normal in the professional geographic map projections' literature; nor does it help novices understand what's going on.
Strebe 01:10, 29 July 2007 (UTC)
Done. Whew. - Ben pcc 17:20, 7 August 2007 (UTC)
I was dealing with an edit to mariner's astrolabe (since moved to its talk page) that referenced "polar projection" on an astrolabe. The link provided by the author was to |polar and [[map projection|projection]]; I changed it to polar projection only to discover no such link existed. I looked at this article and saw no polar projection mentioned.
Not being a cartographer, I looked up polar projection and found it described as a map projection and added a section here with an image. It was removed with the comment as in the section headline. Please explain the difference - it's clear that there is some ambiguity in other references that only a cartographer is likely to explain.
Since the description on talk:mariner's astrolabe is lacking detail on what polar projection means specifically, does anyone know what map projection is appropriate to describe? Thanks for your help. Michael Daly 05:40, 18 October 2007 (UTC)
The article should also mention that these projections are also used for representations of things lying outside a particular frame of reference. For instance, celestial maps and panoramic photographs. SharkD ( talk) 01:12, 15 January 2009 (UTC)
This article needs some attention. I suggest modifications as follows:
1 The term aspect should be introduced for orientation of the projection.
2 The secant projections should not be dismissed so lightly. They are used in almost all projections intended for accurate mapping. (Such as the 60 UTM projections covering most of the globe and the projections used by Great Britain, Australia and many other countries.) In fact the Albers projection shown further up the page is a secant (or modified) projection.
3 As pointed out in the discussion pages the section on cylindrical projections is misleading: only normal cylindrical projections project meridians into vertical lines. As shown in the figures the transverse and oblique Mercator projections project meridians into curved lines. Almost all the comments in this section refer to the normal aspect so the illustration of the oblique aspect is completely out of place. Peter Mercator ( talk) 12:45, 5 April 2009 (UTC)
Peter Mercator, thanks for the efforts. I think we need to refine the edits.
Any equidistant projection is equidistant from two points, not just one. The difference between Maurer's projection and the rest is that the two-point equidistant allows you to specify the two points independently. In the case of the rest, it's always two antipodal points.
Qualifying cylindric as "normal cylindric" seems less than ideal, since most of the principles discussed apply to any aspect of a cylindric. I think we are failing if we do not describe aspect well enough earlier on to handle the situation gracefully in this section. We need to discuss cylindrics generally, not just in normal aspect. For now I'm going to revert just the header.
I also strongly wish not to leave out the explanation that most projections are not physical projections. Perhaps the wording and organization could be better than it was, but it needs to be there.
Cartesian and polar coordinates need links.
Thanks for the efforts. Strebe ( talk) 21:04, 25 November 2009 (UTC)
The gnomonic projection has the property that "The points along a straight line between any two points on the map corresponds to the points along the shortest route between the corresponding points on the globe". That's a bit long-winded, so some people try to convey that idea with the brief phrase "Preserving shortest route". Alas, some people misinterpret "Preserving shortest route" as "preserving the length of the shortest route", or perhaps "preserving the direction of the shortest route", and conclude that "Preserving shortest route - no projectionn exists with this property." Is there some other phrase we could use to give a correct understanding to our readers, or are we forced to use the long-winded description? -- 68.0.124.33 ( talk) 04:45, 16 July 2010 (UTC)
Google Earth and similar applications are very popular these days. What is the name of the projection that we get by "photographing" the Earth from a certain distance, just like GE does? It is the most natural projection, but only half of the Earth can be seen this way. Qorilla ( talk) 20:53, 23 August 2009 (UTC)
The section on classification of projections contains two errors in the statement "pseudoconic (meridians are arcs of circles), pseudocylindrical (meridians are straight lines)". The bracketed 'explanations' are incorrect, as evidenced by the Bonne and the Sinusoidal projections respectively. Replacing 'meridians' by 'parallels' gives correct statements but these are not definitions.Since the remaining projections in this list are unqualified in any way I suggest that the bracketed comments are simply removed until this article is revised thoroughly. I have removed these statements for the time being. Peter Mercator ( talk) 21:28, 1 November 2009 (UTC)
All of the map projections are going into List of map projections. I suggest that the list of examples in each projection type is thinned to a few key examples, linking to the complete list. I will do it myself in a few days if no one objects. Noodle snacks ( talk) 01:29, 8 November 2009 (UTC)
I am a little concerned about the images illustrating the projections in this page and also 'List of projections'. I feel that that any illustration should show the overall shape of the projection and also show a clearly defined graticule (with significant lines such as standard parallels or central meridians emphasised if possible). The land/sea boundary should be clear and colours such that the graticule should be clearly visible over both. There is no need for content on the landmasses: it simply detracts from the a page about projections. The other really important information is the distortion: this would best be shown on a separate Tissot illustration (in the projection file). The thumbnails below show contributions by User:Mdf, User:Stefan Kühn, User:Reisio and User:Strebe: these could be the basis for comments. Sadly the first image fails on almost all the above aspects and is moreover problematic for users with poor sight. (Can you find north New Zealand or Borneo?)
Peter Mercator ( talk) 23:09, 11 November 2009 (UTC)
Exploring all the projection pages reveals that two conventions are in use. That of cartographers, radius (R) explicit in formulae, an that of mathematicians, unit sphere. My own preference is for the former, not least because it follows the usage of Snyder in 'A Working Manual' and 'Flattening', the two most accessible surveys. Peter Mercator ( talk) 23:11, 11 November 2009 (UTC)
I would be grateful if users of this page could comment on an outine of a proposed new page on cylindrical projections at User:Peter Mercator/Draft for cylindrical projections. Please add comments there rather than on this page. Peter Mercator ( talk) 23:14, 11 November 2009 (UTC)
Some map projections completely cover some convex shape. Other map projections have several more or less deep "cuts" in them, in particular the "interrupted sinusoidal projection", the Dymaxion map, and the butterfly maps.
I was hoping this article would tell me: What is the official cartographic name for these "cuts"? Is there an official cartographic name for "creating a slightly different map by slicing off a little area on one side of a cut, and gluing those slices onto the opposite side of a cut"? Why do some maps have "cuts" while others don't? When cartographers make cuts in a map, what sorts of aesthetic considerations do they use when picking the exact place for each cut -- are "try to cut only in the oceans, avoiding the continents" vs. "try to cut only in the continents, avoiding the oceans" the only 2 options? If you know the answers to these questions, would you please edit this article to answer those questions? Thank you. -- 68.0.124.33 ( talk) 05:43, 25 June 2010 (UTC)
Hi. I was thinking of subcategorising the list in compromise projections, with a brief description. The list is too long, and it doesn't hang well in the reader's mind. I was thinking of something like: Projections used by National Geographic (then a list including the years adopted). Then other uninterrupted projections. Then interrupted projections (with brief descriptions). I think this would help create a hierarchy (eg Robinson and van der Grinten have been surpassed by Winkel Tripel in the minds of the cartographers at National Geographic), etc. My view is that any list with more than about 3 or 4 things in it should be categorised and made into sublist. Thoughts? Grj23 ( talk) 07:24, 30 July 2010 (UTC)
Right now Equidistant_conic_projection redirects back here, so clicking it is confusing :( 178.95.30.155 ( talk) 05:01, 20 December 2010 (UTC)
Am I just not seeing it here? 71.199.96.212 ( talk) 04:15, 1 March 2011 (UTC)
This is an interesting article to me as a layperson. Is it possible to explore the 'Which map is best?' section further? For example, what projections are currently favoured by whom? One of the images suggests that "The Robinson projection was adopted by National Geographic Magazine in 1988 but abandoned by them in about 1997 for the Winkel Tripel." Is there more of this type of information available? Thanks. Richdesign ( talk) 08:52, 9 April 2011 (UTC)
Personally, I think the section is pandering. Imagine if the article on fonts had a section called "Which Font is Best?" with a bunch of words devoted to smacking down Arial/Comic Sans/whatever, and then no information whatsoever on what people can agree on? If anything, it needs to be yanked as completely uninformative. Tmcw ( talk) 15:37, 29 November 2011 (UTC)
I do not think these efforts to inject “infinite” into the lede are helpful. The latest, “The family of possible map projections is infinite”, is definitely going in the wrong direction. “Family” is not defined and “family is infinite” means nothing. Technically, “the count of members of the set of possible map projection is infinite”, but this is not an article on mathematics. In particular the lede needs to avoid jargon while being correct. The original objection based on orders of infinity is not relevant, not interesting, and not even correct. Just because there are higher orders of infinity does not mean Aleph 0 is “limited”, and furthermore, where is the proof of which infinity the set belongs to? Can we not mess with something simple, free of jargon, and accurate? Strebe ( talk) 20:53, 19 June 2011 (UTC)
I will be replacing images on the various map projection pages. Presently many are on a satellite composite image from NASA that, while realistic, poorly demonstrates the projections because of dark color and low contrast. I have created a stylization of the same data with much brighter water areas and a light graticule to contrast. See the thumbnail of the example from another article. Some images on some pages are acceptable but differ stylistically from most articles; I will replace these also.
The images will be high resolution and antialiased, with 15° graticules for world projections, red, translucent equator, red tropics, and blue polar circles.
Please discuss agreement or objections over here (not this page). I intend to start these replacements on 13 August. Thank you. Strebe ( talk) 22:43, 6 August 2011 (UTC)
Thought people on this page might like to see this - perception of map projections in popular culture. :) EdwardLane ( talk) 11:21, 17 November 2011 (UTC)
It might be useful to show an image showing how projections works. This site, http://content.answcdn.com/main/content/img/McGrawHill/Aviation/f0426-02.gif or this site http://engineeringtraining.tpub.com/14070/css/14070_185.htm show how the Mercator is done (projected from the center, through a point on the surface onto the wrapping cylinder.) Geoffrey.landis ( talk) 02:05, 29 March 2012 (UTC)
The lede is slightly misleading Where it says "Map projections are necessary for creating maps."
it would be more accurate to say something like "Map projections are necessary for creating any non abstract maps." As I'm pretty sure the london undergound map doesn't use map projection, but once you map it onto the 'real map of london' you obviously are using a projection of some sort.
However the text "Map projections are necessary for creating any non abstract maps." sounds horrible and would possibly still be misleading trying to think of an example of a non abtract map that doesn't use map projection, I can imagine some (though perhaps my definition of abstract map is not perfect). Also interested to note that is a redlink.
Perhaps it should say "Most maps use one Map projection to calculate where to place each object on the map's surface."
Or perhaps "Map projections are necessary for creating scale maps." which I think I'll add now as a simplest start.
Thoughts, suggestions ?
EdwardLane ( talk) 10:43, 8 June 2012 (UTC)
Take the earth, and shrink it to the size of a globe - I don't know but maybe a scale of 1:500000 would be a nice sized globe.
Now let's ignore the fact that even the crust's thickness varies on the underside as well as on the top (mountains and things have roots), and let's pretend the mantle is a sphere.
So lets cut off the crust (down to the mantle) like an orange peel, and flatten it all out - now start cutting (interuptions) everywhere that it doesn't fall perfectly onto a flat surface (the top will not be flat). But even getting the underside to fall 'perfectly' on a flat surface is going to take an awful lot of cutting, and unless you accept a certain amount of imperfection you're never going to finish.
But let's assume you decide that anything less than a kilometer of error is good enough that's what a map ought to show if you are not distorting the 'scale' of any particular place.
But now you end up with a very strange looking orangepeel (lets imagine you've managed to keep most of the cuts in the ocean rather than the land) - so take a photo of that from above, and then put the world back together at full scale again (we may need it later).
So now you look at your photo in some graphics package, and you notice lots of little white bits that make it hard to read, and if you stretch the image a little bit in places you can make it all join up and look more like a normal map, and if you want it to cover the whole page nicely then you need to stretch it a lot in certain spots, but think you can get away with filling in some of the space with seas, no one will notice that unless they are measuring how far away one country is from another (hmm that might matter).
Does that sound about right for getting ones head around the concept is anything obvious missing? Before I try converting that rather silly train of thought into something encyclopedic sounding EdwardLane ( talk) 11:20, 8 June 2012 (UTC)
EdwardLane ( talk) 10:55, 15 June 2012 (UTC)
Just carrying over a comment from the list of map projections talk page. I think we need to try and make a couple of graphics - maybe these two with 3 or 4 examples in each?
One map projection multiple arrangements and One arrangement multiple projections
I think that could help resolve the perennial questions about 'upside down maps' and also the specific one in the link about 'double hemisphere maps' EdwardLane ( talk) 11:27, 11 February 2013 (UTC)
(Copied from my Talk page.)
"The surface of a sphere, or another three-dimensional object".
is that meant to be "(the surface of a sphere), or another three-dimensional object"?
or is it meant to be "the surface of (a sphere, or another three-dimensional object)" ?
Clearly, it is meant to be the second, but the IP user parsed it the first way, and thence concluded that it was erroneous and in need of correction, and became upset when you reverted it to the 'incorrect' version. My edit removes the grammatical ambiguity. Okay? DS ( talk) 00:24, 5 March 2013 (UTC)
I am a native English speaker and a mathematician, so I think I both "understand English [and] the topic well enough". Do not resort to personal attacks. My correction was perfectly justified, as any geometry textbook will make clear to you. A (common) sphere is 2-dimensional, although it often is, but need not be, embedded in higher-dimensional space. Even in these cases it is simply wrong to say that a sphere is 3d.
The sentence to which I objected was: "A map projection is any method of representing the surface of a sphere or other three-dimensional body on a plane." This means, by the law of disjunction, [A map projection is any method of representing the surface of a sphere on a plane] AND [A map projection is any method of representing non-sphere 3d bodies on a plane]. But a sphere is not a 3d body. So the second conjunct is false so the conjunction is false so the proposition is false.
Moreover, this is very bad definition in general, because there is no reason to be arbitrary and talk of projections from 3d geometries. It does make sense to talk about spheres, of course, since this is how we commonly use projections (viz. to make maps). But really the rest of that definition should be changed to make more general. I'll hold off on that until we get some more consensus.
Recall Wittgenstein: "Whereof one cannot speak, thereof one must remain silent." — Preceding unsigned comment added by 184.186.8.148 ( talk) 04:31, 5 March 2013 (UTC)
A sphere is not a three dimensional body. That is silly. Think about how many coordinates it takes to define a point on the surface of the Earth. Two. Cf., e.g. the Wolfram Math Encyclopedia: "Regardless of the choice of convention for indexing the number of dimensions of a sphere, the term "sphere" refers to the surface only, so the usual sphere is a two-dimensional surface. The colloquial practice of using the term "sphere" to refer to the interior of a sphere is therefore discouraged, with the interior of the sphere (i.e., the "solid sphere") being more properly termed a "ball."". This is standard in mathematics. — Preceding unsigned comment added by 184.186.8.148 ( talk) 21:27, 5 March 2013 (UTC)
Do not resort to personal insult. Words matter. Things are true, and they are false. One can easily verify that a common sphere is 2d. I recommend that you do so. — Preceding unsigned comment added by 184.186.8.148 ( talk) 04:32, 6 March 2013 (UTC)
No, you "[g]o away". And while you're gone take a basic class in geometry. You'll see your error. E.g.:
(1) http://www.youtube.com/watch?v=5j0ZxkcVwhk ("Two-dimensional surfaces: the sphere") (2) "Regardless of the choice of convention for indexing the number of dimensions of a sphere, the term "sphere" refers to the surface only, so the usual sphere is a two-dimensional surface." ( http://mathworld.wolfram.com/Sphere.html) (3) WIKIPEDIA: "Just as an ordinary sphere (or 2-sphere) is a two-dimensional surface that forms the boundary of a ball in three dimensions" ( http://en.wikipedia.org/wiki/3-sphere). (4) Princeton: "[A] 3-sphere is a higher-dimensional analogue of a sphere" ( http://www.princeton.edu/~achaney/tmve/wiki100k/docs/3-sphere.html) — Preceding unsigned comment added by 184.186.8.148 ( talk) 07:09, 6 March 2013 (UTC)
Is a common sphere (like the surface of a soccer ball) a two-dimensional or a three-dimensional object? 184.186.8.148 ( talk) 07:18, 6 March 2013 (UTC)
On my talk page, user 184.186.8.148 alleges, “The title of the article is not ‘cartographic map projections’. It is true if that were the article your view would be correct, since cartography is the practice of making maps, which are, at least to the present day, all two-dimensional. But this is an article about map projections generally, and maps can be of any dimension.” This assertion appears to be the root of the recent disputes over scope and terminology of this article.
I dispute the assertion that this article is about something broader than “cartographic map projections” (a term which, by the way, appears in not a single book title and has little presence in the literature for the obvious reason that it is redundant). From the content, clearly the article is not about more than cartographic projections. But I also dispute that the title implies anything different or broader. The terms “map” and “mapping” and “projection” are fundamental to differential geometry, but the term “map projection” means, specifically, cartographic projections. This is confirmed in several ways:
In the domain of pure mathematics “mappings” or “projections” are occasionally referred to as “map projections”, but they do not form any substantial body of literature under that name.
I propose:
1. That the purview of the article remain cartographic projections, without expanding the scope into projections in general;
2. That the nomenclature prevalent in the map projection literature be used for the article;
3. That disputes in nomenclature and definitions be resolved by appeal to the map projection literature;
4. That we wind down discussions of how terms are used in other domains and how other domains treat the mathematics and nomenclature of map projections so that this talk page can focus on its purpose of improving the article.
Strebe ( talk) 07:49, 8 March 2013 (UTC)
I have reverted another edit by 184.186.8.148, who had replaced, in the first line of the artice, "... on a sphere or an ellipsoid" by "on a sphere or other ellipsoid". This is a snobish and useless change whose only effect would be to confuse the non-mathematical readers (that is most of them). May I remind all that this is an article of a general encyclopaedia, not a Bourbakian paper? -- Alvesgaspar ( talk) 11:22, 9 March 2013 (UTC)
Scray's points here all seem like sound ones to me. 184.186.8.148 ( talk) 22:56, 11 March 2013 (UTC)
We should get an airtight, cited definition for “map projection” in place so that we don’t have to debate the scope of this article and its nomenclature. If a new debate crops up we can point to the reference and point to the discussion already resolved. I have all the major and minor texts on map projections in my library, but don’t have access to my library for now. I suggest we discuss the definitions from the major English texts and select one. We can decide after that how to expand on it if we need to. I consider the following texts to be “major” in that they influenced later texts. They are in reverse order of publication date.
Deetz & Adams and Steers went through many editions, but I don’t recall changes in definitions. Maling had two editions, the second one considerably expanding the book, but I don’t recall changes to the early material.
Definitions I have on hand:
Strebe ( talk) 06:51, 15 March 2013 (UTC)
[Moving new inquiry to its own section]
Why is the Fuller projection not listed? — Preceding unsigned comment added by 173.51.214.90 ( talk) 16:51, 5 April 2013 (UTC)
I am itching to reorganise this article, as I feel it could be much improved with some careful changes, but am naturally hesistate as it is clearly a well tended article. It seems to me there are two basics areas to cover:
which appeal to different types of user, and might form a good basis for structuring the article. The section on which map projection is best could be retitled "selecting a map projection". It also ought to cover aspects such as the outline of the map. Then in the later stages rather too many examples in some cases (we have the list of map projections) and too few in others. I have made a modest start by reordering the paras in background section to what I hope will be seen as a more logical order. Treading carefully for now! Marqaz ( talk) 00:18, 17 April 2013 (UTC)
All over wikipedia, a non-standard map projection is used, that is neither equirectangular nor equal-area. Here is an example but there are many more all over the place. [ [4]] What is this projection called? Since it is a wikipedia standard it should be mentioned in the article. What is the formula to convert this thing to equirectangular? Is it the [ Winkle times 3 or whatever]? Would be nice if wikipedia used equirectangular projection for global maps because then they could be used as textures on spheres, but that is a different issue altogether. Apparently wikipedia generates its maps using this http://lert.co.nz/map/ — Preceding unsigned comment added by 2001:15C0:66A3:2:2814:F976:C38:6120 ( talk) 06:28, 25 October 2013 (UTC)
One non-mentioned map projection is that projection that takes the direction of travel to be north, which is east for rotation (but not necesarily for solar orbit). That projection has NS oriented WE, including the space orienations, where E&W are lattitude longtitude reversed (90° greenwhich rotation: top is north). That orientation causes a ´race´ tire orientation, where the north & south poles are hubcaps. Anyone around with such a map? — Preceding unsigned comment added by 190.204.18.169 ( talk) 15:50, 18 February 2014 (UTC)
I made this reversion for the stated reason. To elaborate, the geoid as a model is not about elevations as referred to an ellipsoid. That would mean the model is the ellipsoid. If the geoid itself were the model, mean sea level becomes the model. It would be a more complex surface but still use longitudes and latitudes across that surface, and would still have elevations measure from that. For example, typical hills and valleys have no effect on the geoid, and so they would have elevations to pinpoint positions on them more accurately than just latitude and longitude, whereas ocean surfaces define the geoidal model and therefore would always have 0 elevation—unlike an ellipsoidal model. Strebe ( talk) 01:18, 9 June 2014 (UTC)
References
{{
cite journal}}
: |chapter=
ignored (
help); Cite journal requires |journal=
(
help)
{{
cite journal}}
: |chapter=
ignored (
help); Cite journal requires |journal=
(
help)
This Article does not appear to have a history section where one would obviously be present. Considering the importance of the article, the vast wealth of history on the subject, plus the importance of the development of maps throughout many civilizations, I believe this problem needs to be addressed.
The beginning statements lack citations and make bold claims.
The "Background" section clearly does not give "background" of any kind. This section should be moved to a more appropriate section and re-titled.
This article needs help!
Xavier ( talk) 2:22am, Sunday, November 1st, 2015 (UTC)
[outdent] For example think of any projection that maps a hemisphere to a disk (stereographic projection for example). Consider just the points of that hemisphere, mapped to the disk. Keeping the circumference of the disk fixed, distort the interior of the disk by grabbing the center point C of the disk and moving it to any other interior point C' of the disk, dragging the rest of disk with it as if the disk were stretchable. There are infinitely many points C' to move the center point to, and each one of those mappings changes the relationship of the center (C/C') to the circumference, and is therefore a new projection (a new map of the hemisphere to the disk). This could be made into a formal proof by exhibiting a suitable distortion function (e.g., linear interpolation of the segments CP joining C to boundary points P to the segments joining C'P joining the new position of the center to the same boundary points. -- Elphion ( talk) 12:47, 3 November 2015 (UTC)
Well, one needs to draw the line somewhere. Would you require citation for "The sky is blue" or "Balls fall under the influence of gravity"? That there are an infinite number of projections is so obvious that only Snyder (of the several books on projections that I checked) takes the ink to actually say that -- and not even Snyder bothers to back it up with any argument. (Thanks to Strebe, who added the citation before I could.) Not every sentence really requires citation; else the articles would be so cluttered that they would be hard to read (or at least hard to edit). -- Elphion ( talk) 18:38, 3 November 2015 (UTC)
I think the distinction between azimuthal and retroazimuthal should be clarified. No~w the article seems to be saying that one preserves directions from a central point, while the other preserves directions to a central point, but that sounds like the same thing. MathHisSci ( talk) 21:20, 17 April 2016 (UTC)
In this edit, User:Isambard Kingdom has reintroduced many problems.
The text as it stands is incoherent. I am reverting this again. I would appreciate some reasonable cooperation at addressing these concerns here, on the talk page, where that is supposed to be done. Strebe ( talk) 23:15, 10 March 2017 (UTC)
Does averaging the coordinates of two different equal-area projections make another equal-area projection? If yes, do they have to have the same area scale? — Preceding unsigned comment added by 2A01:119F:2E9:2F00:8C70:6F61:25A8:4750 ( talk) 17:56, 22 March 2017 (UTC)
this seems quite decent at explaining why there are a variety of useful projections which are commonly used - not sure where/how one might include such in an article though - perhaps in external links ? EdwardLane ( talk) 08:55, 12 July 2017 (UTC)
I am very strongly against reincluding that statement. There are many projections that do preserve some geometric property, and in fact the great majority of existing projections must preserve some geometric property to be useful (for example, latitude lines remain parallel). This statement is not sourced and is not limited to just "perspective" projections.-- Jasper Deng (talk) 23:27, 5 October 2019 (UTC)
Classical geometers paid special attention to constructing geometric objects that had been described in some other way. Classically, the only instruments allowed in geometric constructions are the compass and straightedge. Also, every construction had to be complete in a finite number of steps. However, some problems turned out to be difficult or impossible to solve by these means alone, and ingenious constructions using parabolas and other curves, as well as mechanical devices, were found.
Euclidean geometry is geometry in its classical sense. As its models the space of the physical world, it is used in many scientific areas, such as mechanics, astronomy, crystallography, and many technical fields, such as engineering, architecture, geodesy, aerodynamics, and navigation. The mandatory educational curriculum of the majority of nations includes the study of Euclidean concepts such as points, lines, planes, angles, triangles, congruence, similarity, solid figures, circles, and analytic geometry.
Sorry, if you are going to WP:SHOUT at me I’m not going to spend more time attempting to converse with you. Ad hominem is not a way to discredit the fundamental problem that this is a vague statement (what is an “interpretation”?). At this point your arguments are so fallicious it’s not even funny. Chillax, and wait for DRN to do its job.— Jasper Deng (talk) 09:30, 6 October 2019 (UTC)
Currently, the article says that "most" projections "are usually defined in terms of mathematical formulae that have no direct geometric interpretation". I find this statement too vague to be meaningful. What must a geometric interpretation satisfy in order to be "direct"? Is a formula for transforming coordinates somehow illegitimate? How many projections are "most"? XOR'easter ( talk) 17:33, 6 October 2019 (UTC)
For any reasonable interpretation of “direct”, the statement is accurate and meaningful to a wide audience.I must not be part of that wide audience, because now I'm even more confused. Whatever applies to "most" map projections is, by definition, not "exotic". I don't know what "not abstract" would mean when applied to mathematics; even applied math is abstract to some extent. And "classical geometric" would be worse: that sounds like saying most map projections are not expressed as a ruler-and-compass construction — probably true, even more probably irrelevant. XOR'easter ( talk) 20:36, 6 October 2019 (UTC)
Whatever applies to "most" map projections is, by definition, not "exotic"Your argument amounts to, “Most map projections are not exotic; therefore, whatever description is used for them is not exotic; therefore, if I succeed in describing most map projections in terms of bacon, this description would not be exotic.” Of course the interior of any map projection is described by differential geometry, and of course differential geometry is a (modern) form of geometry, but if your thesis is that differential geometry is not exotic to most readers, then obviously my citations disagree. I would be happy to conduct a Mechanical Turk study to this effect if you wish to seriously press this point, as long as you pay for it and my time if you are demonstrated wrong.
I don't know what "not abstract" would mean when applied to mathematics; even applied math is abstract to some extent.This would be an example of pedantry beyond utility, and, honestly, feels like trolling. Abstraction comes in degrees. I am quite certain that you understand this, and I am quite certain that you understand the that applicability of a statement depends upon the degree to which it holds, not to false dichotomies about its binary truth value outside of a mathematical or formal logic proof. Therefore protestations that “I don't know what "not abstract" would mean” ring hollow.
And "classical geometric" would be worse: that sounds like saying most map projections are not expressed as a ruler-and-compass construction — probably true, even more probably irrelevant.If you wish to press this belief in the connotation of classical geometry, I suggest you take that up on Talk:Geometry so that you can get the passages from it that I quote above removed. Good luck.
Isn't it the case that all map projections with the additional property that latitudes become horizontal lines and longitudes become vertical lines DO have a direct geometric meaning: They can be obtained by projecting from the center of the earth onto some particular surface of revolution and then perpendicularly onto a cylinder? I don't see the relevance here. The more important idea is what the lead already says: that most map projections are designed to preserve some important properties of the surface (area, angles, connectivity of land masses...) but that they cannot preserve all such properties. Whether the projection is defined by geometric construction or by mathematical formula does not seem to be an essential property of the projection; the same property can be defined multiple ways. — David Eppstein ( talk) 21:44, 6 October 2019 (UTC)
Isn't it the case that all map projections with the additional property that latitudes become horizontal lines and longitudes become vertical lines DO have a direct geometric meaning: They can be obtained by projecting from the center of the earth onto some particular surface of revolution and then perpendicularly onto a cylinder?If I understand what you are describing here, then yes. That does not seem “direct”, and in any case, projections of the class you describe are not “most projections”. The reason the text about direct geometric interpretation is in there is because, as noted a few times in this sadly lengthy “debate”, the misconception is common that a map projection corresponds to a physical projective “image”. Strebe ( talk) 21:55, 6 October 2019 (UTC)
All the discussion of whether this vague claim is correct is ultimately beside the point -- it's unsourced.The rewrite is still unsourced. Please explain why the four citations I provided early in this debate do not count as sources. Every one of those citations uses “geometry” in the meaning that the text used to. Every one of the categorically disavows that most map projections are merely geometrical. How could this be more clear?
“It is evident, from our definition, that we use the word Projection in a sense much wider than that which geometry gives it. The majority of map projections are not projections at all in the geometric sense.”[2] Hence, merely stating that projections are not “perspective” is WP:SYNTH for ignoring what the texts in the field of map projections actually say about geometry and perspective. We have to suppose that these texts state these things for reasons that make sense for the broad audiences they address.
@ Joel B. Lewis:@ Jasper Deng:@ David Eppstein:@ XOR'easter:@ Alvesgaspar: Wikipedia:Dispute resolution noticeboard#Map projection — Preceding unsigned comment added by Strebe ( talk • contribs)
References
The consensus is that this is not a well-formed RfC. There is no prejudice against starting a new well-formed RfC.
Should the text remain “Few projections in practical use are perspective,” or should it be sourced and its scope be broadened to reflect what the sources say? Strebe ( talk) 22:14, 26 October 2019 (UTC)
This is the first time I have requested an RfC, so I don’t have a nuanced notion of how respondents interpret these guidelines. In response, I gave some constructive criticism about the formulation of this RfC. Your response exhausts any remaining desire on my part to be helpful. -- JBL ( talk) 23:50, 28 October 2019 (UTC)
Despite the name's literal meaning, projection is not limited to perspective projections (...) Few projections in practical use are perspective.) I would mildly support scrapping the last sentence which is not going to be easy to source without some WP:SYNTH (the closest I could find to sourcing would be this USGS report that list 16 map projections including two perspective projection - orthographic and stereographic - but maybe those two are in much bigger use than the other 14 after all). The replacements floated around by the original RfC posters in the above discussion are awful, though. Tigraan Click here to contact me 09:43, 5 November 2019 (UTC)
The text now states, "Flat maps of the globe cannot be created without map projections. All projections of a sphere on a plane necessarily distort the surface in some way and to some extent." It used to not state "flat". User:David Eppstein justifies this with, "Maps on curved paper are obviously possible, and even used (in the form of globes)". This is not correct. (A) Maps onto curved surfaces of whatever sort still require projection; (B) Globes are not made with maps projected onto "curved" paper; they are projected onto normal paper (using a projection tailored for that purpose) which is then warped onto the curved globe; (C) If the projection surface is the globe or a portion of the globe, the projection is a scaling, which is still a projection. Strebe ( talk) 19:07, 30 October 2019 (UTC)
it’s pretty clear what’s going on hereYes: what's going on is that you have adopted an enormously combative and uncollegial approach to editing this article, making the usual process of discussion and consensus very difficult. If you would knock that off and try treating other editors as good-faith contributors who happen to have different views than you, life would be much better. (For example, by striking all the personalized commentary in your second comment.)
buckminster-fuller's projection onto the equal triangles of the icosahedron is listed under "Compromise projections" and commented by: "Compromise projections give up the idea of perfectly preserving metric properties... Most of these types of projections distort shape in the polar regions more than at the equator." if I understood everything well it was b.-m.'s intention to exactly avoid distortions where ever (especially in the polar regions of course) and to preverve metric properties as much as possible by projection onto the 20 equal (!) triangles of the icosahedron... so the only distortion one has there is the minimal one caused by flattening the spherical triangles. so please correct things in my head or the article... thanx! HilmarHansWerner ( talk) 18:14, 10 January 2020 (UTC)
There is no page or article references for the stated projection.
here is a book that has a diagram
here is a web page with links to various projections — Preceding unsigned comment added by 14.200.179.169 ( talk) 12:48, 31 March 2020 (UTC)
In Commons we have problem with old maps and their projections. Wise advices will be needed in here: Commons:Commons:Categories for discussion/2018/01/Category:Maps with unidentified projection-- Estopedist1 ( talk) 10:39, 29 November 2021 (UTC)
"The projections are described in terms of placing a gigantic surface in contact with the Earth" - violation of NPOV? Who defined the surface as gigantic? Is that encyclopedic? Euro2023 ( talk) 23:54, 9 January 2023 (UTC)
"If maps were projected as in light shining through a globe onto a developable surface, then the spacing of parallels would follow a very limited set of possibilities." [5] - How that? Why should there be a limitation? Is there projection of a particular point on a surface that cannot be reached by "light shining through a globe"? Euro2023 ( talk) 15:45, 10 January 2023 (UTC)
I have created a proposal page for Map projections. Please feel free to add your name to the support section, discuss, disseminate, and otherwise edit. Thanks. Strebe ( talk) 01:26, 12 January 2023 (UTC) @ Justinkunimune:@ GeogSage:@ Elphion:@ Fgnievinski:@ Alvesgaspar:@ Paul Koning:@ Peter Mercator:@ EdwardLane:@ Jacobolus:@ Apocheir:
This
level-4 vital article is rated B-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||||||||||||||||||||||
|
Map projection was one of the Geography and places good articles, but it has been removed from the list. There are suggestions below for improving the article to meet the good article criteria. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake. | |||||||||||||
| |||||||||||||
Current status: Delisted good article |
Shouldn't there be somewhere on this page an indication of which projection to use to make a planetary texture to be used on a sphere ? The first place one searches for such a clue is there... I can't write it down for now, because I haven't found it yet, and moreover I don't know editing rules in Wikipedia, so should I write something that I would surely break many of them ^-^ It seems to be called "square" or "rectangular" on many planet generators, but I don't know the proper geographical term and I thought to find it here. That's why I think it would be useful here. Thanks in advance !
Benoît 'Mutos' ROBIN — Preceding unsigned comment added by 77.193.41.178 ( talk) 16:10, 13 November 2011 (UTC)
The images showing examples of projections seem out of place; the images don't relate to the text next to which they are placed. It seems the images placed merely for overall appearance of the article, however this is not very conducive to understanding. —Preceding unsigned comment added by 134.197.40.199 ( talk) 19:43, 15 June 2009 (UTC)
I am not sure whether I am right on this one, but these images seem identical with ESRI's poster on map projections that comes with their book "Getting to know ArcGIS". Someone should verify the copyright of these images. The USGS website does not mention any copyright information.
I don't know if the articles for projections exist, but it might be worth nabbing those that do from Planet math. Mr. Jones 15:05, 8 May 2004 (UTC)
You should put a ":" before the math marker of the Mercator formula, to indent it. Same with the next line starting with phi. – Martin Vermeer
12/29/05
It would be a good idea to add a short section on the history of Map Projections - this is an interesting topic, as it mirrors the evolution of human knowledge over the centuries. Great ingenuity has gone into developing the ideas of map projection to make it more and more useful for navigators and other users.
I have invented a superior map. Everyone will agree that it is the best. How do I submit it? 70.177.90.238 20:40, 11 January 2006 (UTC)
IMHO spherical projection is the more standard mathematical term for this. i've done a redirect from spherical projection to this article, but if noone objects, then i would suggest switching the redirect to the other direction - i.e. "spherical projection" would be the main article. Boud 08:41, 27 April 2006 (UTC)
The article uses maps with America at the centre. I though that the Wikipedia standard was to use maps with Europe/Africa at the centre (because they don't cut Asia in half). If so, does this article deviate from that for a specific reason? And are there names for these maps (I can't find an article on it)? DirkvdM 07:06, 17 August 2006 (UTC)
A while back I heard of a type of projection that was made up of a bunch of triangles, and that by unfolding it a certain way, it showed the world as a chain of continents surrounded by water, or a chain of oceans surrounded by land. Does anyone have any information on this? Stale Fries 00:13, 3 March 2007 (UTC)
I think placing the Dymaxion Map under the heading "compromise projections" is missleading as it is the only unique map among those listed and the description for the section in no way describes the Dymaxion Map. I think part of the confusion above stems from the poor classification of this map. 71.214.83.247 ( talk) 05:46, 3 January 2008 (UTC)
The statement that cylindrical projections have straight meridians is true only for the conventional (projection axis == earth axis) form, not for the transverse or oblique forms. Paul Koning 17:50, 10 May 2007 (UTC)
... whereas most maps show only a small part of the earth. I realize that this is just "a special case" where you only show part of the map, but given the extremely common nature of this issue there should be some specific discussion of what projections are commonly used for smaller maps (and how to choose the parameters). Personally, I'm trying to figure out which projection to use for my map of a country (Guatemala) but the same issue exists even for the smallest, city-scale maps. -- 190.56.85.26 17:10, 11 July 2007 (UTC)
Just found [3] which is much more "useful" from my perspective than this article, as it organizes by purpose rather than by mathematical criteria. I would suggest that this article should keep the initial explanations as is, but the actual projections should be reorganized along the lines of this source.
ps. For my purposes, I've chosen LCC - appropriate for a "taller" country and atlas-style "just looking" maps. Now, I just have to figure out how to enter the parameters into GRASS - it asks for "central", "first", and "second" parallels, which default to 23,33,and 45; I try 15,13,and 17 for a map which will extend 13N to 18N and it doesn't accept them... maybe I need to use negative rather than positive numbers for my false northing and false easting...
pps. Sure it makes hardly any difference for city maps - but you still have to choose one. -- 190.56.85.26 18:48, 11 July 2007 (UTC)
Many articles on projections, such as equirectangular projection, use some kind of "modern notation" in favor of a more understandable x = x(λ, φ), y = y(λ, φ) type of thing that would be easier to understand and is more standard in terms of notation.
This is a notation occasionally used for functions/mappings, but it may not be the best choice here, the shorthand really doesn't make it shorter and only obscures it.
If no one objects I'm intent on fixing all map projection articles that use this convention.
Edit: sorry, forgot to sign. - Ben pcc 22:43, 27 July 2007 (UTC)
I favor this proposal. The so-called "modern notation" is not normal in the professional geographic map projections' literature; nor does it help novices understand what's going on.
Strebe 01:10, 29 July 2007 (UTC)
Done. Whew. - Ben pcc 17:20, 7 August 2007 (UTC)
I was dealing with an edit to mariner's astrolabe (since moved to its talk page) that referenced "polar projection" on an astrolabe. The link provided by the author was to |polar and [[map projection|projection]]; I changed it to polar projection only to discover no such link existed. I looked at this article and saw no polar projection mentioned.
Not being a cartographer, I looked up polar projection and found it described as a map projection and added a section here with an image. It was removed with the comment as in the section headline. Please explain the difference - it's clear that there is some ambiguity in other references that only a cartographer is likely to explain.
Since the description on talk:mariner's astrolabe is lacking detail on what polar projection means specifically, does anyone know what map projection is appropriate to describe? Thanks for your help. Michael Daly 05:40, 18 October 2007 (UTC)
The article should also mention that these projections are also used for representations of things lying outside a particular frame of reference. For instance, celestial maps and panoramic photographs. SharkD ( talk) 01:12, 15 January 2009 (UTC)
This article needs some attention. I suggest modifications as follows:
1 The term aspect should be introduced for orientation of the projection.
2 The secant projections should not be dismissed so lightly. They are used in almost all projections intended for accurate mapping. (Such as the 60 UTM projections covering most of the globe and the projections used by Great Britain, Australia and many other countries.) In fact the Albers projection shown further up the page is a secant (or modified) projection.
3 As pointed out in the discussion pages the section on cylindrical projections is misleading: only normal cylindrical projections project meridians into vertical lines. As shown in the figures the transverse and oblique Mercator projections project meridians into curved lines. Almost all the comments in this section refer to the normal aspect so the illustration of the oblique aspect is completely out of place. Peter Mercator ( talk) 12:45, 5 April 2009 (UTC)
Peter Mercator, thanks for the efforts. I think we need to refine the edits.
Any equidistant projection is equidistant from two points, not just one. The difference between Maurer's projection and the rest is that the two-point equidistant allows you to specify the two points independently. In the case of the rest, it's always two antipodal points.
Qualifying cylindric as "normal cylindric" seems less than ideal, since most of the principles discussed apply to any aspect of a cylindric. I think we are failing if we do not describe aspect well enough earlier on to handle the situation gracefully in this section. We need to discuss cylindrics generally, not just in normal aspect. For now I'm going to revert just the header.
I also strongly wish not to leave out the explanation that most projections are not physical projections. Perhaps the wording and organization could be better than it was, but it needs to be there.
Cartesian and polar coordinates need links.
Thanks for the efforts. Strebe ( talk) 21:04, 25 November 2009 (UTC)
The gnomonic projection has the property that "The points along a straight line between any two points on the map corresponds to the points along the shortest route between the corresponding points on the globe". That's a bit long-winded, so some people try to convey that idea with the brief phrase "Preserving shortest route". Alas, some people misinterpret "Preserving shortest route" as "preserving the length of the shortest route", or perhaps "preserving the direction of the shortest route", and conclude that "Preserving shortest route - no projectionn exists with this property." Is there some other phrase we could use to give a correct understanding to our readers, or are we forced to use the long-winded description? -- 68.0.124.33 ( talk) 04:45, 16 July 2010 (UTC)
Google Earth and similar applications are very popular these days. What is the name of the projection that we get by "photographing" the Earth from a certain distance, just like GE does? It is the most natural projection, but only half of the Earth can be seen this way. Qorilla ( talk) 20:53, 23 August 2009 (UTC)
The section on classification of projections contains two errors in the statement "pseudoconic (meridians are arcs of circles), pseudocylindrical (meridians are straight lines)". The bracketed 'explanations' are incorrect, as evidenced by the Bonne and the Sinusoidal projections respectively. Replacing 'meridians' by 'parallels' gives correct statements but these are not definitions.Since the remaining projections in this list are unqualified in any way I suggest that the bracketed comments are simply removed until this article is revised thoroughly. I have removed these statements for the time being. Peter Mercator ( talk) 21:28, 1 November 2009 (UTC)
All of the map projections are going into List of map projections. I suggest that the list of examples in each projection type is thinned to a few key examples, linking to the complete list. I will do it myself in a few days if no one objects. Noodle snacks ( talk) 01:29, 8 November 2009 (UTC)
I am a little concerned about the images illustrating the projections in this page and also 'List of projections'. I feel that that any illustration should show the overall shape of the projection and also show a clearly defined graticule (with significant lines such as standard parallels or central meridians emphasised if possible). The land/sea boundary should be clear and colours such that the graticule should be clearly visible over both. There is no need for content on the landmasses: it simply detracts from the a page about projections. The other really important information is the distortion: this would best be shown on a separate Tissot illustration (in the projection file). The thumbnails below show contributions by User:Mdf, User:Stefan Kühn, User:Reisio and User:Strebe: these could be the basis for comments. Sadly the first image fails on almost all the above aspects and is moreover problematic for users with poor sight. (Can you find north New Zealand or Borneo?)
Peter Mercator ( talk) 23:09, 11 November 2009 (UTC)
Exploring all the projection pages reveals that two conventions are in use. That of cartographers, radius (R) explicit in formulae, an that of mathematicians, unit sphere. My own preference is for the former, not least because it follows the usage of Snyder in 'A Working Manual' and 'Flattening', the two most accessible surveys. Peter Mercator ( talk) 23:11, 11 November 2009 (UTC)
I would be grateful if users of this page could comment on an outine of a proposed new page on cylindrical projections at User:Peter Mercator/Draft for cylindrical projections. Please add comments there rather than on this page. Peter Mercator ( talk) 23:14, 11 November 2009 (UTC)
Some map projections completely cover some convex shape. Other map projections have several more or less deep "cuts" in them, in particular the "interrupted sinusoidal projection", the Dymaxion map, and the butterfly maps.
I was hoping this article would tell me: What is the official cartographic name for these "cuts"? Is there an official cartographic name for "creating a slightly different map by slicing off a little area on one side of a cut, and gluing those slices onto the opposite side of a cut"? Why do some maps have "cuts" while others don't? When cartographers make cuts in a map, what sorts of aesthetic considerations do they use when picking the exact place for each cut -- are "try to cut only in the oceans, avoiding the continents" vs. "try to cut only in the continents, avoiding the oceans" the only 2 options? If you know the answers to these questions, would you please edit this article to answer those questions? Thank you. -- 68.0.124.33 ( talk) 05:43, 25 June 2010 (UTC)
Hi. I was thinking of subcategorising the list in compromise projections, with a brief description. The list is too long, and it doesn't hang well in the reader's mind. I was thinking of something like: Projections used by National Geographic (then a list including the years adopted). Then other uninterrupted projections. Then interrupted projections (with brief descriptions). I think this would help create a hierarchy (eg Robinson and van der Grinten have been surpassed by Winkel Tripel in the minds of the cartographers at National Geographic), etc. My view is that any list with more than about 3 or 4 things in it should be categorised and made into sublist. Thoughts? Grj23 ( talk) 07:24, 30 July 2010 (UTC)
Right now Equidistant_conic_projection redirects back here, so clicking it is confusing :( 178.95.30.155 ( talk) 05:01, 20 December 2010 (UTC)
Am I just not seeing it here? 71.199.96.212 ( talk) 04:15, 1 March 2011 (UTC)
This is an interesting article to me as a layperson. Is it possible to explore the 'Which map is best?' section further? For example, what projections are currently favoured by whom? One of the images suggests that "The Robinson projection was adopted by National Geographic Magazine in 1988 but abandoned by them in about 1997 for the Winkel Tripel." Is there more of this type of information available? Thanks. Richdesign ( talk) 08:52, 9 April 2011 (UTC)
Personally, I think the section is pandering. Imagine if the article on fonts had a section called "Which Font is Best?" with a bunch of words devoted to smacking down Arial/Comic Sans/whatever, and then no information whatsoever on what people can agree on? If anything, it needs to be yanked as completely uninformative. Tmcw ( talk) 15:37, 29 November 2011 (UTC)
I do not think these efforts to inject “infinite” into the lede are helpful. The latest, “The family of possible map projections is infinite”, is definitely going in the wrong direction. “Family” is not defined and “family is infinite” means nothing. Technically, “the count of members of the set of possible map projection is infinite”, but this is not an article on mathematics. In particular the lede needs to avoid jargon while being correct. The original objection based on orders of infinity is not relevant, not interesting, and not even correct. Just because there are higher orders of infinity does not mean Aleph 0 is “limited”, and furthermore, where is the proof of which infinity the set belongs to? Can we not mess with something simple, free of jargon, and accurate? Strebe ( talk) 20:53, 19 June 2011 (UTC)
I will be replacing images on the various map projection pages. Presently many are on a satellite composite image from NASA that, while realistic, poorly demonstrates the projections because of dark color and low contrast. I have created a stylization of the same data with much brighter water areas and a light graticule to contrast. See the thumbnail of the example from another article. Some images on some pages are acceptable but differ stylistically from most articles; I will replace these also.
The images will be high resolution and antialiased, with 15° graticules for world projections, red, translucent equator, red tropics, and blue polar circles.
Please discuss agreement or objections over here (not this page). I intend to start these replacements on 13 August. Thank you. Strebe ( talk) 22:43, 6 August 2011 (UTC)
Thought people on this page might like to see this - perception of map projections in popular culture. :) EdwardLane ( talk) 11:21, 17 November 2011 (UTC)
It might be useful to show an image showing how projections works. This site, http://content.answcdn.com/main/content/img/McGrawHill/Aviation/f0426-02.gif or this site http://engineeringtraining.tpub.com/14070/css/14070_185.htm show how the Mercator is done (projected from the center, through a point on the surface onto the wrapping cylinder.) Geoffrey.landis ( talk) 02:05, 29 March 2012 (UTC)
The lede is slightly misleading Where it says "Map projections are necessary for creating maps."
it would be more accurate to say something like "Map projections are necessary for creating any non abstract maps." As I'm pretty sure the london undergound map doesn't use map projection, but once you map it onto the 'real map of london' you obviously are using a projection of some sort.
However the text "Map projections are necessary for creating any non abstract maps." sounds horrible and would possibly still be misleading trying to think of an example of a non abtract map that doesn't use map projection, I can imagine some (though perhaps my definition of abstract map is not perfect). Also interested to note that is a redlink.
Perhaps it should say "Most maps use one Map projection to calculate where to place each object on the map's surface."
Or perhaps "Map projections are necessary for creating scale maps." which I think I'll add now as a simplest start.
Thoughts, suggestions ?
EdwardLane ( talk) 10:43, 8 June 2012 (UTC)
Take the earth, and shrink it to the size of a globe - I don't know but maybe a scale of 1:500000 would be a nice sized globe.
Now let's ignore the fact that even the crust's thickness varies on the underside as well as on the top (mountains and things have roots), and let's pretend the mantle is a sphere.
So lets cut off the crust (down to the mantle) like an orange peel, and flatten it all out - now start cutting (interuptions) everywhere that it doesn't fall perfectly onto a flat surface (the top will not be flat). But even getting the underside to fall 'perfectly' on a flat surface is going to take an awful lot of cutting, and unless you accept a certain amount of imperfection you're never going to finish.
But let's assume you decide that anything less than a kilometer of error is good enough that's what a map ought to show if you are not distorting the 'scale' of any particular place.
But now you end up with a very strange looking orangepeel (lets imagine you've managed to keep most of the cuts in the ocean rather than the land) - so take a photo of that from above, and then put the world back together at full scale again (we may need it later).
So now you look at your photo in some graphics package, and you notice lots of little white bits that make it hard to read, and if you stretch the image a little bit in places you can make it all join up and look more like a normal map, and if you want it to cover the whole page nicely then you need to stretch it a lot in certain spots, but think you can get away with filling in some of the space with seas, no one will notice that unless they are measuring how far away one country is from another (hmm that might matter).
Does that sound about right for getting ones head around the concept is anything obvious missing? Before I try converting that rather silly train of thought into something encyclopedic sounding EdwardLane ( talk) 11:20, 8 June 2012 (UTC)
EdwardLane ( talk) 10:55, 15 June 2012 (UTC)
Just carrying over a comment from the list of map projections talk page. I think we need to try and make a couple of graphics - maybe these two with 3 or 4 examples in each?
One map projection multiple arrangements and One arrangement multiple projections
I think that could help resolve the perennial questions about 'upside down maps' and also the specific one in the link about 'double hemisphere maps' EdwardLane ( talk) 11:27, 11 February 2013 (UTC)
(Copied from my Talk page.)
"The surface of a sphere, or another three-dimensional object".
is that meant to be "(the surface of a sphere), or another three-dimensional object"?
or is it meant to be "the surface of (a sphere, or another three-dimensional object)" ?
Clearly, it is meant to be the second, but the IP user parsed it the first way, and thence concluded that it was erroneous and in need of correction, and became upset when you reverted it to the 'incorrect' version. My edit removes the grammatical ambiguity. Okay? DS ( talk) 00:24, 5 March 2013 (UTC)
I am a native English speaker and a mathematician, so I think I both "understand English [and] the topic well enough". Do not resort to personal attacks. My correction was perfectly justified, as any geometry textbook will make clear to you. A (common) sphere is 2-dimensional, although it often is, but need not be, embedded in higher-dimensional space. Even in these cases it is simply wrong to say that a sphere is 3d.
The sentence to which I objected was: "A map projection is any method of representing the surface of a sphere or other three-dimensional body on a plane." This means, by the law of disjunction, [A map projection is any method of representing the surface of a sphere on a plane] AND [A map projection is any method of representing non-sphere 3d bodies on a plane]. But a sphere is not a 3d body. So the second conjunct is false so the conjunction is false so the proposition is false.
Moreover, this is very bad definition in general, because there is no reason to be arbitrary and talk of projections from 3d geometries. It does make sense to talk about spheres, of course, since this is how we commonly use projections (viz. to make maps). But really the rest of that definition should be changed to make more general. I'll hold off on that until we get some more consensus.
Recall Wittgenstein: "Whereof one cannot speak, thereof one must remain silent." — Preceding unsigned comment added by 184.186.8.148 ( talk) 04:31, 5 March 2013 (UTC)
A sphere is not a three dimensional body. That is silly. Think about how many coordinates it takes to define a point on the surface of the Earth. Two. Cf., e.g. the Wolfram Math Encyclopedia: "Regardless of the choice of convention for indexing the number of dimensions of a sphere, the term "sphere" refers to the surface only, so the usual sphere is a two-dimensional surface. The colloquial practice of using the term "sphere" to refer to the interior of a sphere is therefore discouraged, with the interior of the sphere (i.e., the "solid sphere") being more properly termed a "ball."". This is standard in mathematics. — Preceding unsigned comment added by 184.186.8.148 ( talk) 21:27, 5 March 2013 (UTC)
Do not resort to personal insult. Words matter. Things are true, and they are false. One can easily verify that a common sphere is 2d. I recommend that you do so. — Preceding unsigned comment added by 184.186.8.148 ( talk) 04:32, 6 March 2013 (UTC)
No, you "[g]o away". And while you're gone take a basic class in geometry. You'll see your error. E.g.:
(1) http://www.youtube.com/watch?v=5j0ZxkcVwhk ("Two-dimensional surfaces: the sphere") (2) "Regardless of the choice of convention for indexing the number of dimensions of a sphere, the term "sphere" refers to the surface only, so the usual sphere is a two-dimensional surface." ( http://mathworld.wolfram.com/Sphere.html) (3) WIKIPEDIA: "Just as an ordinary sphere (or 2-sphere) is a two-dimensional surface that forms the boundary of a ball in three dimensions" ( http://en.wikipedia.org/wiki/3-sphere). (4) Princeton: "[A] 3-sphere is a higher-dimensional analogue of a sphere" ( http://www.princeton.edu/~achaney/tmve/wiki100k/docs/3-sphere.html) — Preceding unsigned comment added by 184.186.8.148 ( talk) 07:09, 6 March 2013 (UTC)
Is a common sphere (like the surface of a soccer ball) a two-dimensional or a three-dimensional object? 184.186.8.148 ( talk) 07:18, 6 March 2013 (UTC)
On my talk page, user 184.186.8.148 alleges, “The title of the article is not ‘cartographic map projections’. It is true if that were the article your view would be correct, since cartography is the practice of making maps, which are, at least to the present day, all two-dimensional. But this is an article about map projections generally, and maps can be of any dimension.” This assertion appears to be the root of the recent disputes over scope and terminology of this article.
I dispute the assertion that this article is about something broader than “cartographic map projections” (a term which, by the way, appears in not a single book title and has little presence in the literature for the obvious reason that it is redundant). From the content, clearly the article is not about more than cartographic projections. But I also dispute that the title implies anything different or broader. The terms “map” and “mapping” and “projection” are fundamental to differential geometry, but the term “map projection” means, specifically, cartographic projections. This is confirmed in several ways:
In the domain of pure mathematics “mappings” or “projections” are occasionally referred to as “map projections”, but they do not form any substantial body of literature under that name.
I propose:
1. That the purview of the article remain cartographic projections, without expanding the scope into projections in general;
2. That the nomenclature prevalent in the map projection literature be used for the article;
3. That disputes in nomenclature and definitions be resolved by appeal to the map projection literature;
4. That we wind down discussions of how terms are used in other domains and how other domains treat the mathematics and nomenclature of map projections so that this talk page can focus on its purpose of improving the article.
Strebe ( talk) 07:49, 8 March 2013 (UTC)
I have reverted another edit by 184.186.8.148, who had replaced, in the first line of the artice, "... on a sphere or an ellipsoid" by "on a sphere or other ellipsoid". This is a snobish and useless change whose only effect would be to confuse the non-mathematical readers (that is most of them). May I remind all that this is an article of a general encyclopaedia, not a Bourbakian paper? -- Alvesgaspar ( talk) 11:22, 9 March 2013 (UTC)
Scray's points here all seem like sound ones to me. 184.186.8.148 ( talk) 22:56, 11 March 2013 (UTC)
We should get an airtight, cited definition for “map projection” in place so that we don’t have to debate the scope of this article and its nomenclature. If a new debate crops up we can point to the reference and point to the discussion already resolved. I have all the major and minor texts on map projections in my library, but don’t have access to my library for now. I suggest we discuss the definitions from the major English texts and select one. We can decide after that how to expand on it if we need to. I consider the following texts to be “major” in that they influenced later texts. They are in reverse order of publication date.
Deetz & Adams and Steers went through many editions, but I don’t recall changes in definitions. Maling had two editions, the second one considerably expanding the book, but I don’t recall changes to the early material.
Definitions I have on hand:
Strebe ( talk) 06:51, 15 March 2013 (UTC)
[Moving new inquiry to its own section]
Why is the Fuller projection not listed? — Preceding unsigned comment added by 173.51.214.90 ( talk) 16:51, 5 April 2013 (UTC)
I am itching to reorganise this article, as I feel it could be much improved with some careful changes, but am naturally hesistate as it is clearly a well tended article. It seems to me there are two basics areas to cover:
which appeal to different types of user, and might form a good basis for structuring the article. The section on which map projection is best could be retitled "selecting a map projection". It also ought to cover aspects such as the outline of the map. Then in the later stages rather too many examples in some cases (we have the list of map projections) and too few in others. I have made a modest start by reordering the paras in background section to what I hope will be seen as a more logical order. Treading carefully for now! Marqaz ( talk) 00:18, 17 April 2013 (UTC)
All over wikipedia, a non-standard map projection is used, that is neither equirectangular nor equal-area. Here is an example but there are many more all over the place. [ [4]] What is this projection called? Since it is a wikipedia standard it should be mentioned in the article. What is the formula to convert this thing to equirectangular? Is it the [ Winkle times 3 or whatever]? Would be nice if wikipedia used equirectangular projection for global maps because then they could be used as textures on spheres, but that is a different issue altogether. Apparently wikipedia generates its maps using this http://lert.co.nz/map/ — Preceding unsigned comment added by 2001:15C0:66A3:2:2814:F976:C38:6120 ( talk) 06:28, 25 October 2013 (UTC)
One non-mentioned map projection is that projection that takes the direction of travel to be north, which is east for rotation (but not necesarily for solar orbit). That projection has NS oriented WE, including the space orienations, where E&W are lattitude longtitude reversed (90° greenwhich rotation: top is north). That orientation causes a ´race´ tire orientation, where the north & south poles are hubcaps. Anyone around with such a map? — Preceding unsigned comment added by 190.204.18.169 ( talk) 15:50, 18 February 2014 (UTC)
I made this reversion for the stated reason. To elaborate, the geoid as a model is not about elevations as referred to an ellipsoid. That would mean the model is the ellipsoid. If the geoid itself were the model, mean sea level becomes the model. It would be a more complex surface but still use longitudes and latitudes across that surface, and would still have elevations measure from that. For example, typical hills and valleys have no effect on the geoid, and so they would have elevations to pinpoint positions on them more accurately than just latitude and longitude, whereas ocean surfaces define the geoidal model and therefore would always have 0 elevation—unlike an ellipsoidal model. Strebe ( talk) 01:18, 9 June 2014 (UTC)
References
{{
cite journal}}
: |chapter=
ignored (
help); Cite journal requires |journal=
(
help)
{{
cite journal}}
: |chapter=
ignored (
help); Cite journal requires |journal=
(
help)
This Article does not appear to have a history section where one would obviously be present. Considering the importance of the article, the vast wealth of history on the subject, plus the importance of the development of maps throughout many civilizations, I believe this problem needs to be addressed.
The beginning statements lack citations and make bold claims.
The "Background" section clearly does not give "background" of any kind. This section should be moved to a more appropriate section and re-titled.
This article needs help!
Xavier ( talk) 2:22am, Sunday, November 1st, 2015 (UTC)
[outdent] For example think of any projection that maps a hemisphere to a disk (stereographic projection for example). Consider just the points of that hemisphere, mapped to the disk. Keeping the circumference of the disk fixed, distort the interior of the disk by grabbing the center point C of the disk and moving it to any other interior point C' of the disk, dragging the rest of disk with it as if the disk were stretchable. There are infinitely many points C' to move the center point to, and each one of those mappings changes the relationship of the center (C/C') to the circumference, and is therefore a new projection (a new map of the hemisphere to the disk). This could be made into a formal proof by exhibiting a suitable distortion function (e.g., linear interpolation of the segments CP joining C to boundary points P to the segments joining C'P joining the new position of the center to the same boundary points. -- Elphion ( talk) 12:47, 3 November 2015 (UTC)
Well, one needs to draw the line somewhere. Would you require citation for "The sky is blue" or "Balls fall under the influence of gravity"? That there are an infinite number of projections is so obvious that only Snyder (of the several books on projections that I checked) takes the ink to actually say that -- and not even Snyder bothers to back it up with any argument. (Thanks to Strebe, who added the citation before I could.) Not every sentence really requires citation; else the articles would be so cluttered that they would be hard to read (or at least hard to edit). -- Elphion ( talk) 18:38, 3 November 2015 (UTC)
I think the distinction between azimuthal and retroazimuthal should be clarified. No~w the article seems to be saying that one preserves directions from a central point, while the other preserves directions to a central point, but that sounds like the same thing. MathHisSci ( talk) 21:20, 17 April 2016 (UTC)
In this edit, User:Isambard Kingdom has reintroduced many problems.
The text as it stands is incoherent. I am reverting this again. I would appreciate some reasonable cooperation at addressing these concerns here, on the talk page, where that is supposed to be done. Strebe ( talk) 23:15, 10 March 2017 (UTC)
Does averaging the coordinates of two different equal-area projections make another equal-area projection? If yes, do they have to have the same area scale? — Preceding unsigned comment added by 2A01:119F:2E9:2F00:8C70:6F61:25A8:4750 ( talk) 17:56, 22 March 2017 (UTC)
this seems quite decent at explaining why there are a variety of useful projections which are commonly used - not sure where/how one might include such in an article though - perhaps in external links ? EdwardLane ( talk) 08:55, 12 July 2017 (UTC)
I am very strongly against reincluding that statement. There are many projections that do preserve some geometric property, and in fact the great majority of existing projections must preserve some geometric property to be useful (for example, latitude lines remain parallel). This statement is not sourced and is not limited to just "perspective" projections.-- Jasper Deng (talk) 23:27, 5 October 2019 (UTC)
Classical geometers paid special attention to constructing geometric objects that had been described in some other way. Classically, the only instruments allowed in geometric constructions are the compass and straightedge. Also, every construction had to be complete in a finite number of steps. However, some problems turned out to be difficult or impossible to solve by these means alone, and ingenious constructions using parabolas and other curves, as well as mechanical devices, were found.
Euclidean geometry is geometry in its classical sense. As its models the space of the physical world, it is used in many scientific areas, such as mechanics, astronomy, crystallography, and many technical fields, such as engineering, architecture, geodesy, aerodynamics, and navigation. The mandatory educational curriculum of the majority of nations includes the study of Euclidean concepts such as points, lines, planes, angles, triangles, congruence, similarity, solid figures, circles, and analytic geometry.
Sorry, if you are going to WP:SHOUT at me I’m not going to spend more time attempting to converse with you. Ad hominem is not a way to discredit the fundamental problem that this is a vague statement (what is an “interpretation”?). At this point your arguments are so fallicious it’s not even funny. Chillax, and wait for DRN to do its job.— Jasper Deng (talk) 09:30, 6 October 2019 (UTC)
Currently, the article says that "most" projections "are usually defined in terms of mathematical formulae that have no direct geometric interpretation". I find this statement too vague to be meaningful. What must a geometric interpretation satisfy in order to be "direct"? Is a formula for transforming coordinates somehow illegitimate? How many projections are "most"? XOR'easter ( talk) 17:33, 6 October 2019 (UTC)
For any reasonable interpretation of “direct”, the statement is accurate and meaningful to a wide audience.I must not be part of that wide audience, because now I'm even more confused. Whatever applies to "most" map projections is, by definition, not "exotic". I don't know what "not abstract" would mean when applied to mathematics; even applied math is abstract to some extent. And "classical geometric" would be worse: that sounds like saying most map projections are not expressed as a ruler-and-compass construction — probably true, even more probably irrelevant. XOR'easter ( talk) 20:36, 6 October 2019 (UTC)
Whatever applies to "most" map projections is, by definition, not "exotic"Your argument amounts to, “Most map projections are not exotic; therefore, whatever description is used for them is not exotic; therefore, if I succeed in describing most map projections in terms of bacon, this description would not be exotic.” Of course the interior of any map projection is described by differential geometry, and of course differential geometry is a (modern) form of geometry, but if your thesis is that differential geometry is not exotic to most readers, then obviously my citations disagree. I would be happy to conduct a Mechanical Turk study to this effect if you wish to seriously press this point, as long as you pay for it and my time if you are demonstrated wrong.
I don't know what "not abstract" would mean when applied to mathematics; even applied math is abstract to some extent.This would be an example of pedantry beyond utility, and, honestly, feels like trolling. Abstraction comes in degrees. I am quite certain that you understand this, and I am quite certain that you understand the that applicability of a statement depends upon the degree to which it holds, not to false dichotomies about its binary truth value outside of a mathematical or formal logic proof. Therefore protestations that “I don't know what "not abstract" would mean” ring hollow.
And "classical geometric" would be worse: that sounds like saying most map projections are not expressed as a ruler-and-compass construction — probably true, even more probably irrelevant.If you wish to press this belief in the connotation of classical geometry, I suggest you take that up on Talk:Geometry so that you can get the passages from it that I quote above removed. Good luck.
Isn't it the case that all map projections with the additional property that latitudes become horizontal lines and longitudes become vertical lines DO have a direct geometric meaning: They can be obtained by projecting from the center of the earth onto some particular surface of revolution and then perpendicularly onto a cylinder? I don't see the relevance here. The more important idea is what the lead already says: that most map projections are designed to preserve some important properties of the surface (area, angles, connectivity of land masses...) but that they cannot preserve all such properties. Whether the projection is defined by geometric construction or by mathematical formula does not seem to be an essential property of the projection; the same property can be defined multiple ways. — David Eppstein ( talk) 21:44, 6 October 2019 (UTC)
Isn't it the case that all map projections with the additional property that latitudes become horizontal lines and longitudes become vertical lines DO have a direct geometric meaning: They can be obtained by projecting from the center of the earth onto some particular surface of revolution and then perpendicularly onto a cylinder?If I understand what you are describing here, then yes. That does not seem “direct”, and in any case, projections of the class you describe are not “most projections”. The reason the text about direct geometric interpretation is in there is because, as noted a few times in this sadly lengthy “debate”, the misconception is common that a map projection corresponds to a physical projective “image”. Strebe ( talk) 21:55, 6 October 2019 (UTC)
All the discussion of whether this vague claim is correct is ultimately beside the point -- it's unsourced.The rewrite is still unsourced. Please explain why the four citations I provided early in this debate do not count as sources. Every one of those citations uses “geometry” in the meaning that the text used to. Every one of the categorically disavows that most map projections are merely geometrical. How could this be more clear?
“It is evident, from our definition, that we use the word Projection in a sense much wider than that which geometry gives it. The majority of map projections are not projections at all in the geometric sense.”[2] Hence, merely stating that projections are not “perspective” is WP:SYNTH for ignoring what the texts in the field of map projections actually say about geometry and perspective. We have to suppose that these texts state these things for reasons that make sense for the broad audiences they address.
@ Joel B. Lewis:@ Jasper Deng:@ David Eppstein:@ XOR'easter:@ Alvesgaspar: Wikipedia:Dispute resolution noticeboard#Map projection — Preceding unsigned comment added by Strebe ( talk • contribs)
References
The consensus is that this is not a well-formed RfC. There is no prejudice against starting a new well-formed RfC.
Should the text remain “Few projections in practical use are perspective,” or should it be sourced and its scope be broadened to reflect what the sources say? Strebe ( talk) 22:14, 26 October 2019 (UTC)
This is the first time I have requested an RfC, so I don’t have a nuanced notion of how respondents interpret these guidelines. In response, I gave some constructive criticism about the formulation of this RfC. Your response exhausts any remaining desire on my part to be helpful. -- JBL ( talk) 23:50, 28 October 2019 (UTC)
Despite the name's literal meaning, projection is not limited to perspective projections (...) Few projections in practical use are perspective.) I would mildly support scrapping the last sentence which is not going to be easy to source without some WP:SYNTH (the closest I could find to sourcing would be this USGS report that list 16 map projections including two perspective projection - orthographic and stereographic - but maybe those two are in much bigger use than the other 14 after all). The replacements floated around by the original RfC posters in the above discussion are awful, though. Tigraan Click here to contact me 09:43, 5 November 2019 (UTC)
The text now states, "Flat maps of the globe cannot be created without map projections. All projections of a sphere on a plane necessarily distort the surface in some way and to some extent." It used to not state "flat". User:David Eppstein justifies this with, "Maps on curved paper are obviously possible, and even used (in the form of globes)". This is not correct. (A) Maps onto curved surfaces of whatever sort still require projection; (B) Globes are not made with maps projected onto "curved" paper; they are projected onto normal paper (using a projection tailored for that purpose) which is then warped onto the curved globe; (C) If the projection surface is the globe or a portion of the globe, the projection is a scaling, which is still a projection. Strebe ( talk) 19:07, 30 October 2019 (UTC)
it’s pretty clear what’s going on hereYes: what's going on is that you have adopted an enormously combative and uncollegial approach to editing this article, making the usual process of discussion and consensus very difficult. If you would knock that off and try treating other editors as good-faith contributors who happen to have different views than you, life would be much better. (For example, by striking all the personalized commentary in your second comment.)
buckminster-fuller's projection onto the equal triangles of the icosahedron is listed under "Compromise projections" and commented by: "Compromise projections give up the idea of perfectly preserving metric properties... Most of these types of projections distort shape in the polar regions more than at the equator." if I understood everything well it was b.-m.'s intention to exactly avoid distortions where ever (especially in the polar regions of course) and to preverve metric properties as much as possible by projection onto the 20 equal (!) triangles of the icosahedron... so the only distortion one has there is the minimal one caused by flattening the spherical triangles. so please correct things in my head or the article... thanx! HilmarHansWerner ( talk) 18:14, 10 January 2020 (UTC)
There is no page or article references for the stated projection.
here is a book that has a diagram
here is a web page with links to various projections — Preceding unsigned comment added by 14.200.179.169 ( talk) 12:48, 31 March 2020 (UTC)
In Commons we have problem with old maps and their projections. Wise advices will be needed in here: Commons:Commons:Categories for discussion/2018/01/Category:Maps with unidentified projection-- Estopedist1 ( talk) 10:39, 29 November 2021 (UTC)
"The projections are described in terms of placing a gigantic surface in contact with the Earth" - violation of NPOV? Who defined the surface as gigantic? Is that encyclopedic? Euro2023 ( talk) 23:54, 9 January 2023 (UTC)
"If maps were projected as in light shining through a globe onto a developable surface, then the spacing of parallels would follow a very limited set of possibilities." [5] - How that? Why should there be a limitation? Is there projection of a particular point on a surface that cannot be reached by "light shining through a globe"? Euro2023 ( talk) 15:45, 10 January 2023 (UTC)
I have created a proposal page for Map projections. Please feel free to add your name to the support section, discuss, disseminate, and otherwise edit. Thanks. Strebe ( talk) 01:26, 12 January 2023 (UTC) @ Justinkunimune:@ GeogSage:@ Elphion:@ Fgnievinski:@ Alvesgaspar:@ Paul Koning:@ Peter Mercator:@ EdwardLane:@ Jacobolus:@ Apocheir: