Training opportunities. Interestingly, all of Earth’s lines of longitude are great circles, yet the Equator is the only line of latitude that is a great circle. Such curves are said to be “intrinsically” straight. The distance between two points in Euclidean space is the length of a straight line between them, but on the sphere there are no straight lines. Because the map projection necessarily requires some distortion, simple Euclidian geometry often is not applicable.
Spherical geometry is the study of geometric objects located on the surface of a sphere. The great-circle distance or orthodromic distance is the shortest distance between two points on the surface of a sphere, measured along the surface of the sphere (as opposed to a straight line through the sphere's interior).
Sections of the sphere that do not contain a diameter are called small circles . Great circles through the poles are called lines of longitude (or meridians). Since they must follow the circumference of the Earth to divide it, great circles are about 40,000 kilometers (24,854 miles) in length along meridians. While geometry would say that the great circle path is always best, physics sometimes gets in the way. In the world of spherical geometry, two parallel lines on great circles intersect twice, the sum of the three angles of a triangle on the sphere's surface exceed 180° due to positive curvature, and the shortest route to get from one point to another is not a straight line on a map but a line that follows the minor arc of a great circle.
A great circle is the largest circle that can be drawn on any given sphere. A great circle is a section of a sphere that contains a diameter of the sphere (Kern and Bland 1948, p. 87).
Until the 19th century ships generally sailed along rhumb lines, which made use of prevailing winds and fixed compass headings. This is a consequence of the properties of a sphere, in which the shortest distances on the surface are great circle routes. The great circle equidistant to each is then the equator. This is also known as a great circle when a sphere is used. GREAT_ELLIPTIC — The line on a spheroid (ellipsoid) defined by the intersection at the surface by a plane that passes through the center of the spheroid and the start and endpoints of a segment. Great Circle Lesson For Teachers 9th - 11th Guide your class in this computer-based activity to explore Earth's spherical geometry and the concept of the Great Circle. The great circle is the largest possible circle able to be formed along a sphere, such as the Earth’s equator. Circles on the sphere that are parallel (i.e. Great circle definition is - a circle formed on the surface of a sphere by the intersection of a plane that passes through the center of the sphere; specifically : such a circle on the surface of the earth an arc of which connecting two terrestrial points constitutes the shortest distance on … Great circles are the “straight lines” of spherical geometry. Any diameter of any great circle coincides with a diameter of the sphere, and therefore all great circles have the same center and circumference as each other.