Secant plane

Animation showing the circular secant planes of the ellipsoid

A secant plane is a plane containing a nontrivial section of a sphere or an ellipsoid, or such a plane that a sphere is projected onto. Secant planes are similar to tangent planes, which contact the sphere's surface at a point, while secant planes contact the surface along curves.

The two-dimensional representations of secant planes are secant lines, the lines that join two distinct points on a curve.

Applications

Comparison of tangent and secant cylindrical, conic and azimuthal map projections with standard parallels shown in red

Secant planes are used in map projections. The secant plane intersects a globe along a small circle with no distortion, forming a standard parallel which has true scale.[1]

See also

  • Circular section
  • Circular segment
  • Spherical cap
  • Tangent space

References

  1. ^ "Map projection - types and distortion". geokov.com. Retrieved 2016-11-02.

External links

  • Tangents and Secants in Map Projections