Mapmakers have developed hundreds of map projections, over several thousand years. Although the projection procedure inevitably introduces systematic spatial distortions, particular types of distortion can be minimized to suit the geographic scope and intended use of the map data. Since the mass of the earth is not uniform at all points, and the direction of gravity changes, the shape of the geoid is irregular. A map projection is a geometric function that transforms the earths curved, ellipsoidal surface onto a flat, 2dimensional plane.
The quartic authalic is a pseudo cylindrical equalarea projection used. A map projection is any of many methods used in cartography mapmaking to represent the twodimensional curved surface of the earth or other body on a plane. Supported linear units, map projections, and projected. A new pseudocylindrical equalarea projection for adaptive. This gives the illusion of a threedimensional globe. Eth cas ris module from gis data to interactive web maps institute of cartography and geoinformation. Although they can represent size, shape, distance and directions of the earth features with reasonable accuracy, globes are not practical or suitable for many applications. The map is made by equally dividing a spherical surface into 96 triangles, transferring it to a tetrahedron while maintaining area proportions, and unfolding it onto a rectangle. In the transformation from the ellipsoid to the authalic sphere. The show link will display the projection in single view mode. Adaptive composite map projections accepted author. Media in category images of map projections the following 200 files are in this category, out of 247 total. This pseudo cylindrical equalarea projection is primarily used for thematic maps of the.
Pdf in this paper, we introduce some known map projections from a model of. Types of map projections the number of map projections made possible is limitless, and hundreds have been published. All map projections distort the surface in some fashion. The epsg geodetic parameter dataset is a structured. Azimuthal projection projection on which the azimuth or direction from a given central point to any other point is shown correctly. Since the earth is roughly the shape of an oblate spheroid, map projections are necessary for creating maps of the earth or parts of the earth that are represented on a plane such as a piece of paper or a computer screen. Map projection concerns the science of mathematical cartography, the techniques by which the earths dimensions, shape and features are translated in map form, be that twodimensional paper or two or three dimensional electronic representations. A new pseudocylindrical equalarea projection for adaptive composite map projections article pdf available in international journal of geographical information science 2812. This usually includes lines delineat ing meridians and parallels, as required by some definitions of a map projection, but it may not, depending on the purpose of the map. Actual size of the projection minus the black or white background. Understanding map projections landing page for kartoweb.
Authagraph is an approximately equalarea world map projection invented by japanese architect hajime narukawa in 1999. Its key features are its resemblance to the popular robinson projection and continents with a visually. The quartic authalic is a pseudocylindrical equalarea projection, created by modifying the lambert azimuthal. A new pseudocylindrical equalarea projection for adaptive composite map projections bojan savric and bernhard jenny college of earth, ocean, and atmospheric sciences, oregon state university, corvallis, or, usa. The three main families of map projections unwrapping the sphere to a plane. Geographic coordinate systems, datums, spheroids, prime meridians, and angular units of measure current as of arcgis version 9. Although there has been no dearth of valuable books describing a wide range of map projec tions, an album of map projections is the. Although the earth is best represented by a spheroid, the earth is sometimes treated as a sphere to make mathematical calculations easier. It is perpendicular to the direction of gravity pull. In cartography, a map projection is a way to flatten a globes surface into a plane in order to make a map.
The authalic latitude f3, on a sphere having the same surface area as the. Pdf the equal earth map projection is a new equalarea pseudocylindrical projection for world maps. Coordinate systems, projections, and transformations. Planar perspective projection, viewed from infinity. A geographic coordinate systems pdf file which contains lists of supported gcs. Distortion in size and area near the projection limit appears more realistic than almost any other projection, except the vertical nearside perspective. Encyclopedia article about authalic map projection by the free dictionary. Dl tr3624 00 map projection equations by frederick pearson i warfare analysis department march 1977. The geoid is defined as the surface of the earths gravity field, which is approximately the same as mean sea level. Map projections ibm informix spatial data types support many map projections. Commonly, a map projection is a systematic transformation of the latitudes and longitudes of locations on the surface of a sphere or an ellipsoid into locations on a plane. In map projection, equalarea maps preserve area measure, generally distorting shapes in order to do that. The central focus of this book is on the theory of map projections.
A sound knowledge of map projections and grids requires an understanding of the mathematical nature of projections and the size and shape of the earth, since in our context. The quartic authalic is a pseudo cylindrical equalarea projection used primarily for thematic maps of the world. It is also modeled more accurately as an oblate spheroid or an ellipsoid. This requires a systematic transformation of the latitudes and longitudes of locations from the surface of the globe into locations on a plane. Comparing map projection apart from the center of its projection. The nomenclature and classification of map projections csiss. Mapping the ellipsoid to sphere and from sphere to plane double projection, authalic projection 257 91 general mapping equations ellipsoidofrevolution to plane 257 911 the setup of the mapping equations ellipsoidofrevolution to plane 257 912 the metric tensor of the ellipsoidofrevolution, the first differential form 258.
A sphere, unlike a polyhedron, cone, or cylinder, cannot be reformed into a plane. This perspective projection views the globe from an infinite distance. To sort the list, click the headline in the table head. Vii january 1944 pages 190 200 the nomenclature and classification of map projections l. A map projection is a systematic transformation of the latitudes and longitudes. Depending on the purpose of the map, some distortions are acceptable and others are not.
The term projection here refers to any function defined on the earths surface and with values on the plane, and not necessarily a geometric projection. It is currently incomplete in four ways, two diagrams are missing. Pdf a new pseudocylindrical equalarea projection for. A map projection is a systematic transformation of the latitudes and longitudes of positions on the surface of the earth to a. A new pseudocylindrical equalarea projection for adaptive composite map projections bojan savric and bernhard jenny college of earth, ocean, and atmospheric. Aspect conceptual placement of a projection system in relation to the earths axis direct, normal, polar, equatorial, oblique, and so on. Mathematics and implementation details for the equal earth. S areal distortion a x b 2 maximum angular distortion 2u u 28 blue circle represents distortion at a point on a map. In order to portray the surface of a round body on a twodimensional flat plane, you must first define a developable surface i. This booklet provides a conceptual introduction to map projections and geographic reference systems. Supported linear units, map projections, and projected coordinate systems map projection parameters name sphereonly parameters key below aitoff yes lam0 albers equal area conic lam0 phi1 phi2 phi0 azimuthal equidistant lam0 phi0 behrmann yes lam0 bonne lam0 phi1 cassini lam0 phi0 k0 craster parabolic yes lam0 cube yes lam0 option.
This is a summary of map projections that have articles of their own on wikipedia or that are otherwise notable. An album of map projections should enable read ers to sharpen and in some cases to correct their knowledge of the distances, directions, and relative areas of the world. Although they can represent size, shape, distance and directions of the earth features with reasonable accuracy, globes are not. The mercator projection is a cylindrical projection that was developed for navigation purposes. Three large families of map projection, plus several smaller ones, are generally acknowledged. Authalic map projection article about authalic map.
Because there is no limit to the number of possible map projections, there can be no comprehensive list. The mercator projection was used for its portrayal of direction and shape, so it was helpful to the sailors of that time. Equalarea maps are also called equivalent or authalic several equivalent projections were developed in an attempt to minimize the distortion of countries and continents of planet earth, keeping the area constant. The following table lists a representative sample of the map projections supported by the ibm informix spatial data types. A map projection is a systematic representation of all or part of the surface of a round body, especially the earth, on a plane.
175 1457 342 578 51 1169 1342 500 1468 1019 517 1157 1544 1078 52 440 1179 594 1499 763 1464 291 1304 799 513 176 641 705 132 192 10 88 1051 136 4 597 1036 616 441 1165 661 302