orthodrome | sphere geodesic | sphere point-point picking

A great circle is a section of a sphere that contains a diameter of the sphere. Sections of the sphere that do not contain a diameter are called small circles. A great circle becomes a straight line in a gnomonic projection. The shortest path between two points on a sphere, also known as an orthodrome, is a segment of a great circle. To find the great circle (geodesic) distance between two points located at latitude δ and longitude λ of (δ_1, λ_1) and (δ_2, λ_2) on a sphere of radius a, convert spherical coordinates to Cartesian coordinates using r_i = a[cos λ_i cos δ_i sin λ_i cos δ_i sin δ_i].

geodesic | great sphere | loxodrome | Mikusiński's problem | oblate spheroid geodesic | point-point distance--3-dimensional | pseudocircle | small circle | sphere | spheric section