Projecting the Earth: A Diamond or Tetragon?

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Discussion Overview

The discussion revolves around the challenges of projecting the Earth onto a flat map, exploring the potential for alternative shapes such as a diamond or tetragon to achieve more accurate representations. It encompasses theoretical considerations of map projections and the inherent distortions involved in representing a spherical surface on a plane.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the Earth could be represented more accurately on a flat map by using a diamond shape or a rotated tetragon, questioning the current methods of projection.
  • Another participant notes that there are many existing methods for projecting the Earth onto a map, referencing external sources for further reading.
  • It is stated that it is impossible to project a sphere onto a plane without some distortion, citing principles from Differential Geometry regarding ruled surfaces.
  • One participant discusses the curvature of a sphere, indicating that a sphere missing a point is not flat, and highlights the distinction between topological and geometrical properties.
  • Examples of conformal mappings, such as stereographic and Mercator projections, are mentioned as methods to project a sphere onto a plane.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of using alternative shapes for map projections and the implications of curvature on projection methods. The discussion remains unresolved regarding the best approach to achieve accurate flat representations of the Earth.

Contextual Notes

There are limitations in the assumptions made about the nature of curvature and the properties of different projection methods. The discussion does not resolve the complexities involved in achieving distortion-free projections.

k_squared
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I was thinking, I know that the Earth has to be distorted when projected on a flat map because the space nearer the poles of the Earth does not have a much circumference but is expending the same amount of flat space. Could you not do an accurate flat projection by making the Earth a diamond, or a diamond with curved sides? Or some possible combination of 'rotated' tetragon?

I hope this is the appropriate forum. Either way, thanks a lot!
 
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However, there is no way to project a sphere onto a plane without distorting some portion. It is shown in Differential Geometry that a surface can be mapped onto a plane without distortion if and only if, through every point in the surface, there exist a least one straight line that is completely contained in the surface (a "ruled surface").
 
It comes from the fact that a sphere has curvature (4π if I am not mistaken) while a sphere missing a point is flat, doesn't it?
 
espen180 said:
It comes from the fact that a sphere has curvature (4π if I am not mistaken) while a sphere missing a point is flat, doesn't it?

A sphere missing a point is not flat. Topologically it is the same as a plane but not geometrically.

The best you can do is map the sphere- point conformally onto the plane. Stereographic and Mercator projections are examples.
 

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