The Chamberlin trimetric projection is a map projection where three points are fixed on the globe and the points on the sphere are mapped onto a plane by

triangulation In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle me ...

. It was developed in 1946 by Wellman Chamberlin for the National Geographic Society. Chamberlin was chief

cartographer Cartography (; from grc, χάρτης , "papyrus, sheet of paper, map"; and , "write") is the study and practice of making and using maps. Combining science, aesthetics and technique, cartography builds on the premise that reality (or an im ...

for the Society from 1964 to 1971. The projection's principal feature is that it compromises between distortions of area, direction, and distance. A Chamberlin trimetric map therefore gives an excellent overall sense of the region being mapped. Many National Geographic Society maps of single continents use this projection. As originally implemented, the projection algorithm begins with the selection of three points near the outer boundary of the area to be mapped. From these three base points, the true distances to a point on the mapping area are calculated. The distances from each of the three base points are then drawn on the plane by compass circles. Unlike triangulation on a plane where three such compass circles will intersect at a unique point, the compass circles from a sphere do not intersect precisely at a point. A small triangle is generated from the intersections, and the center of this triangle is calculated as the mapped point. A Chamberlin trimetric projection map was originally obtained by graphically mapping points at regular intervals of latitude and longitude, with shorelines and other features then mapped by interpolation. Based on the principles of the projection, precise, but lengthy, mathematical formulas were later developed for calculating this projection by

computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...

for a spherical earth. The Chamberlin trimetric projection is neither

conformal Conformal may refer to: * Conformal (software), in ASIC Software * Conformal coating in electronics * Conformal cooling channel, in injection or blow moulding * Conformal field theory in physics, such as: ** Boundary conformal field theory ...

nor equal-area. Rather, the projection was conceived to minimize distortion of distances everywhere with the side-effect of balancing between areal equivalence and conformality. This projection is not appropriate for mapping the entire sphere because the outer boundary would loop and overlap itself in most configurations. In some cases, the Chamberlin trimetric projection is difficult to distinguish visually from the Lambert azimuthal equal-area projection centered on the same area.

References

External links

The Chamberlin Trimetric Projection
- Implementations of the projection using Matlab scripts.
The Chamberlin Trimetric Projection
- Notes on the projection from a cartography class at

Colorado State University Colorado State University (Colorado State or CSU) is a public land-grant research university in Fort Collins, Colorado. It is the flagship university of the Colorado State University System. Colorado State University is classified among "R1: ...

. {{DEFAULTSORT:Chamberlin Trimetric Projection Map projections

See also

References

External links