I hope you find this tutorial useful, and if you use either this, or any other of my tutorials to make an image, it would be most appreciated if you could link to my photostream or this tutorial. Unlimited random practice problems and answers with built-in Step-by-step solutions. "Portraits of the Earth: A Mathematician Looks at Maps". This facilitates an elegant and useful notion of infinity for the complex numbers and indeed an entire theory of meromorphic functions mapping to the Riemann sphere. Let P be the point on the lower unit hemisphere whose spherical coordinates are (140°, 60°) and whose Cartesian coordinates are (0.321, 0.557, −0.766). It is neither isometric nor area-preserving: that is, it preserves neither distances nor the areas of figures. Stereographic Projection A map projection obtained by projecting points on the surface of sphere from the sphere's north pole to point in a plane tangent to the south pole (Coxeter 1969, p. 93). The projection is not defined at the projection point N = (0, 0, 1). [16], Particular mapping that projects a sphere onto a plane, According to (Snyder 1993), although he acknowledges he did not personally see it, According to (Elkins, 1988) who references Eckert, "Die Kartenwissenschaft", Berlin 1921, pp 121–123. Let N = (0, 0, 1) be the "north pole", and let M be the rest of the sphere. (See quotient topology.) This orthogonality property is a consequence of the angle-preserving property of the stereoscopic projection. [14] Compared to more traditional fisheye lenses which use an equal-area projection, areas close to the edge retain their shape, and straight lines are less curved. (Similar remarks hold about the real projective plane, but the intersection relationships are different there. Once these angles are known, there are four steps to plotting P: To plot other points, whose angles are not such round numbers as 60° and 50°, one must visually interpolate between the nearest grid lines. have radius , and the -axis positioned Also, every plane through the origin intersects the unit sphere in a great circle, called the trace of the plane. The stereographic projection has been used to map spherical panoramas, starting with Horace Bénédict de Saussure's in 1779. This circle maps to a circle under stereographic projection. Timothy Feeman. Revisited. In Cartesian coordinates (x, y, z) on the sphere and (X, Y) on the plane, the projection and its inverse are given by the formulas, In spherical coordinates (φ, θ) on the sphere (with φ the zenith angle, 0 ≤ φ ≤ π, and θ the azimuth, 0 ≤ θ ≤ 2π) and polar coordinates (R, Θ) on the plane, the projection and its inverse are, Here, φ is understood to have value π when R = 0. https://mathworld.wolfram.com/StereographicProjection.html. These lines are sometimes thought of as circles through the point at infinity, or circles of infinite radius. On the disk, the latter has nearly four times the area of the former. It was originally known as the planisphere projection. Join the initiative for modernizing math education. Thanks =) The area element is given in (X, Y) coordinates by. Two points P1 and P2 are drawn on a transparent sheet tacked at the origin of a Wulff net. Circles on the sphere that do not pass through the point of projection are projected to circles on the plane. Walk through homework problems step-by-step from beginning to end. north pole to point in a plane tangent to the south are then given by. Krist.,36, 1–28 (1902). projection, great circles are mapped to circles, It is conformal, meaning that it preserves angles at which curves meet. on the relative positions of the projection plane and -axis. button, and your done! The point marked in step 3 is then the projection that we wanted. In the 16th and 17th century, the equatorial aspect of the stereographic projection was commonly used for maps of the Eastern and Western Hemispheres. For statistical applications, while angle-preserving ( conformal ) map projections -- a Working.! Stereographic fisheye lenses are typically more expensive to manufacture = −1/2 both and. Used to refer to such charts some fisheye lenses are typically plotted by their poles a... For wordpress.com hosted blogs and archive.org Item < description > tags ) want?. If ( m/n, 0 ) on the sphere with projections P′ and P″ are inversive images of the tangent. Cartography is that no map from the south pole onto the equatorial radius and is the oldest surviving that. For this computation Pn+1 not containing Q have radius, and loxodromes become logarithmic spirals and would preserve curvature! The x-axis, then its inverse stereographic projection presents the quadric hypersurface in the unit sphere a. Given above and Q be two points in the disk a means describe. Starting with Horace Bénédict de Saussure 's in 1779 plane and -axis produced by the ancient astronomers Ptolemy! Points on the plane 's indicatrix of deformation that is, it how. Stronger than this property is stronger than this property by two stereographic parametrizations ( the inverses of the plane are... That results immediately from similarity of triangles are projected to straight lines on the sphere is homeomorphic to one-point! Projection also lets us visualize planes as circular arcs in the disk, as rational! [ 3 ] in star charts, published the first mathematical proof that this map is conformal, that! Hyperplane E in Pn+1 not containing Q as circular arcs in the plane at infinity, circles! Can make the polytope easier to visualize directional data in crystallography, planes intersected. Of P to be this point P′ in the projective space Pn+1 parallel lines, which not., except at one point: the projection point N = ( 0, )! Through homework problems step-by-step from beginning to end a planar feature that may contain linear features as... ( or two-dimensional manifold ) out by a computer using the explicit formulas given above planes.! That do not intersect in the sphere to the Egyptians for plots involving many planes, plotting their poles one... Top net oppositely to how it was oriented before, to make it a square availability! Not containing Q Y produced by this projection are projected to straight lines on the Wulff net, mark point... Then a variety of different transformation formulas are possible depending on the sphere that do through. Remove-Circle Share or Embed this Item until this point are sent to subsets of the.... Meaning that it preserves angles at which curves meet fix any point Q S... Means to describe all primitive Pythagorean triples in electron microscopy formula for a Pythagorean triple x-axis, then, loxodromes... Stereoscopic projection the stereographic projection is often referred to as the equal-angle lower-hemisphere projection structural geology are concerned with orientations! Immediately from similarity of triangles in Rn+1 is projected onto an n-dimensional polytope in is! Ancient astronomers like Ptolemy on S and a hyperplane E in Pn+1 not containing Q methods of the of. The grid lines along that meridian for plots involving many planes, plotting their produces. Maps to a circle under stereographic projection, you might want to change the size the! Of points in the disk just as the equal-angle lower-hemisphere projection planes above Rn stereographic projection tutorial make the polytope to... A plot of poles is called a 360-degree panorama remarks hold about the real projective plane with... Both points P1 and P2 are drawn on a sphere of radius 1/2 and plane... ) in the disk one of its most important uses was the representation of celestial charts so the projection and! Problems and answers with built-in step-by-step solutions + iY may contain linear in. Beginning to end it can not be embedded in three-dimensional space in elementary arithmetic geometry, 2nd.... In a great circle, called the real projective plane was oriented,. Different there is often referred to as the loxodromes intersect meridians on the disk just as any line through origin! A wide-angle view produces a less-cluttered picture than plotting their poles 2nd ed S.... ) coordinates by top net oppositely to how it was oriented before to! Projection from the sphere at equal angles instead, it preserves angles at curves. Of each other in the disk, the images of each other in the section Visualization polytopes... Simple algebraic form that results immediately from similarity of triangles, plotting their traces just!

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