3DSoftware.com  >   Cartography  >  Map Projections Map Projections

Map Projection Pages

The following web pages on this web site contain extensive information about map projections from U.S. Geological Survey documents.

General Information

 General overview of map projection concepts. Includes examples. Definitions of map projection terms. How to locate a point on Earth using meridians, parallels, and grids. Accounting for the Earth not being perfectly round.
The rest of this page lists links to specific map projections, listed by types of projections which were categorized by John P. Snyder (see book references at the end of this page). All images on this page are from those books.
 Terms Used In This Page: Meridian  – Longitude line.       Parallel  – Latitude line.       Conformal  – Projection on which all angles at each point are preserved.       Equal-Area  – Projection on which the areas of all regions are shown in the same proportion to their true areas. Shapes may be greatly distorted.       Equidistant  – Projection that maintains constant scale along all great circles from one or two points. See the Definitions Page

 Cylindrical projections are used primarily for complete world maps, or for maps along narrow strips of a great circle arc, such as the Equator, a meridian, or an oblique great circle. In the normal (regular) aspect, meridians and parallels are straight lines. Regular Transverse Oblique

 This widely used projection simply consists of plotting longitude and latitude points on an evenly spaced X,Y (Cartesian) graph. Meridians and parallels are equally spaced, forming squares. A modification of the Plate Carree (Geographic) projection, with the meridians spaced closer together, forming rectangles with the parallels instead of squares. The Cassini map projection is the transverse aspect of the Plate Carree projection. Equidistant. The Mercator projection has area distortion, but is the only map projection that shows true compass bearings for navigation. Historically used in combination with the Gnomic. Conformal. The transverse aspect of the Mercator projection, used to map quadrangles throughout the world. Conformal. The oblique aspect of the Mercator projection, used to map regions having greater extent in an oblique direction, such as Hawaii and the Alaska panhandle. Conformal. A cylindrical projection used for world maps in British atlases. Looks like the Mercator, but takes up less space on the printed page. A cylindrical projection used for world maps in American atlases. Similar to the Gall. Easy to construct equal-area maps, used for education purposes. Equal-area.

 Like the Regular Cylindrical projections, the Pseudocylindrical (or “false cylindrical”) projections have latitude lines that are straight and parallel, and longitude lines (meridians) that are equally spaced. But in the pseudocylindrical, only the central meridian is straight; all other longitudinal meridians are curved. Some of these projections are interrupted to reduce curvature of meridians. Interrupted Sinusoidal

Used for world maps.

Used for thematic and other world maps in numerous atlases and textbooks and for sheet maps. Equal-area.

Used for thematic world maps in the Soviet World Atlas of 1937. Some recent use for climatic maps by U.S. publishers. Equal-area.

Used for world maps, and maps of continents and other regions especially those bordering the Equator. Used in atlases to map Africa and South America. Also used for interruptions (see above), transformations, and in combination with other projections. Equal-area, Equally spaced parallels.

An equal-area projection of the Earth bounded with an ellipse. The basis of several other map projections. Example of interrupted form to show oceans. Equal-area.

Interrupted projection used for world maps. A merging of the Mollweide and Sinusoidal projections. Equal-area.

Based on the Mollweide and Sinusoidal projections. Equal-area.

A flat pole projection with equally spaced meridians as portions of semi-ellipses. Equal-area.

Used for thematic world maps in textbooks. Meridians are equally spaced parabolas intersecting at the poles. Equal-area.

Flat-Polar Sinusoidal Projection. Basis of merged projections by McBryde. Equal-area.

World map interrupted to show oceans or land masses, by McBryde. Equal-area.

 To show a region for which the greatest extent is from east to west in the temperate zones, conic projections are usually preferable to cylindrical projections.

 The most common projection in atlases for small countries. It was also used to map the Soviet Union. One of the most commonly used projections for maps of the conterminous United States. Equal-area. A conic projection with one standard parallel, and the pole as a point. Equal-area. Used for large-scale mapping of regions of predominantly east-west extent, including topographic quadrangles for many of the U.S. State Plane Coordinate System zones. Conformal. Shows North and South America in one map. Conformal. The Polyconic projection shows meridians curved, not straight A pseudoconic projection, popular in atlases for maps of continents until the mid-20th century. Equal-area. Used in the 16th and 17th centuries. Mathematically similar to the Bonne. Equal-area.

 While cylindrical and conic projections are related to cylinders and cones wrapped around the globe, the azimuthal projections are formed onto a plane which is tangent to the globe.                   by John P. Snyder, U.S. Geological Survey Polar Oblique

 Perspective Azimuthal Projections: The Earth as viewed from deep space. Perspective projection. The Earth as viewed from near space (for example, as viewed from the position of a satellite). Perspective. Used to map polar regions, and large continent-sized areas that extend similarly in all directions. Also has many other applications. Conformal, Perspective. Also called the “Gnomic,” it diplays all great circles as straight lines, showing the shortest distance between any two points. All great circles are shown as straight lines, not merely those passing through the center of the projection. Historically used for navigation. Perspective. Nonperspective Azimuthal Projections: Areas are correct, and the overall scale variation is less than that found on the major perspective azimuthals. Equal-area. Distances from the center of the projection to any other point are shown correctly. Overall scale variation is moderate compared to the perspective azimuthals. Equidistant. The mimimum-error azimuthal projection of the region enclosed by a great or small circle of chosen radius from a given center. Nonperspective, neither conformal nor equal area. Minimum-error. Modified Azimuthal Projections: Used for whole-world maps. Less shearing on the outer meridians near the poles than there is on pseudocylindrical projections. Equal-area. Also used for whole-world maps. A modification of the Hammer projection. Used for world maps, such as climatic maps prepared by the U.S. Department of Commerce. Equal-area. Whole-world map, derived from the equatorial aspect of the Lambert Azimuthal Equal-Area projection. Equal-area. Whole world maps showing continents grouped near the center. Derived from the oblique aspect of the Hammer projection. Equal-area. Used for areas that can be contained within an oval shape to minimize the scale distortions in the area. Conformal. A geometric tilting of the Gnomonic. Rarely used, but can be used to find the location of a ship at sea with a radio direction finder and known locations of radio transmitters. Shows true distances, but not true azimuths, from either of two chosen points to any other point on the map. Has received moderate use and interest.

 The world enclosed in a circle. Suitable for mapping imagery from Landsat and other vertically scanning satellites. Also for mapping the groundtrack of orbiting satellites. Cylindrical or Conic Mathematical projection for displaying the U.S. with minimal distortion. Developed by John P. Snyder. Most of the world, projected onto a portion of a torus ring (similar to a doughnut).

 An Album of Map Projections USGS Professional Paper 1453 by John P. Snyder and Philip M. Voxland 1994, 249 pp. Map Projections: A Working Manual USGS Professional Paper 1395 by John P. Snyder 1997, 383 pp.   Note: John P. Snyder was the U.S. Government's leading cartographer.