Map projection definition of map projection by the free. There is no limit to the number of possible map projections 1 projections are a subject of several pure mathematical fields, including differential geometry, projective geometry, and manifolds. Mercator projection definition is a conformal map projection of which the meridians are usually drawn parallel to each other and the parallels of latitude are straight lines whose distance from each other increases with their distance from the equator. Map projection 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. When a map projection is in effect, the data coordinates for the current graphics window or device correspond to longitude xaxis and latitude yaxis in fractional degrees, and the oplot, plots, xyouts, and contour procedures plot in terms of longitude and latitude. Depending on the purpose of the map, some distortions may be less bad. Projected on a map formed into a cone gives a conical map projection. The azimuthal map projection is angular given three points on a map a, b, and c the azimuth from point b to point c dictates the angle someone would have to look or travel in order to get to a. When projected on a planar map it produces an azimuthal or zenithal map projections. Scale increases perpendicular to the radii toward the periphery. The equal earth map projection is a new equalarea pseudocylindrical projection for world maps.
Jan 06, 2017 learn what a map projection is, why they are used and what impact they have on maps gis systems. 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. The use of orthographic projection in cartography dates back to antiquity. Dec 27, 2002 a map projection is one of many methods used to represent the 3dimensional surface of the earth or other round body on a 2dimensional plane in cartography mapmaking. For larger scale maps, including topographic quadrangles and the state base map series, conformal projections such as the transverse mercator and the. A map projection is a way of showing the surface of a threedimensional sphere on a flat surface.
Geological survey usgs now uses several of the more common projections for its published maps. Every distinct map projection distorts in a distinct way, by definition. Because there is no limit to the number of possible map projections, there can be no comprehensive list. A map projection is a method for taking the curved surface of the earth and displaying it on something flat, like a computer screen or a piece of paper. Non projection definition, a projecting or protruding part. Apr 25, 2017 mercator projection is an example of cylindrical projection which became a standard map projection because of its ability to represent lines of steady course.
After decades of using only one map projection, the polyconic, for its mapping program, the u. Red circles on the map confirm that map scale is equal along both standard parallels. The lambert azimuthal equalarea projection is mathematically based on a plane tangent to the earth. Map projection simple english wikipedia, the free encyclopedia. Map projections explained a beginners guide youtube. This process is typically, but not necessarily, a mathematical procedure some methods are graphically based. Zenithal projection definition at, a free online dictionary with pronunciation, synonyms and translation. Conic projection definition of conic projection by the free. Feb 21, 2011 an overview of different map projections. Map makers have devised methods for taking points on the curved surface of the earth and projecting them onto a flat surface.
Map projection definition of map projection by the free dictionary. Every projection has its own set of advantages and disadvantages. Other measurement system properties such as a spheroid of reference, a datum, and projection parameters like one or more standard parallels, a central meridian, and possible shifts in the x and ydirections. Mercator projection definition of mercator projection by. These methods enable map makers to control the distortion that results from creating a flat map of the round earth. Jun 06, 2017 map projection 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.
Understanding map projections landing page for kartoweb. The map is a cylindrical projection that standardized nautical map projection. Map projection is the method of transferring the graticule of latitude and longitude on a plane surface. Map projection and coordinate system tasks common coordinate system and map projection tasks in arcgis here is a series of links to guidance on how to perform a number of common coordinate system tasks in arcgis. It is also known as the babinet projection, homalographic projection, homolographic projection, and elliptical projection. The stereographic map projection is conformal but not. The mollweide projection is an equalarea, pseudocylindrical map projection generally used for global maps of the world or night sky. Mercator distorts the size of geographical objects because its linear scale increases with the increase in latitude. Space oblique mercator maps show a satellites ground track as a curved line that is continuously true to scale as orbiting continues. Homolographic projection definition is an equalarea map projection.
We will taker a closer look at the popular mercator projection and examine how the projection. Definition and uses of map projections flashcards quizlet. Defining the coordinate systems, reprojecting, and transforming datasets coordinate system definition and projection. Zenithal projection definition of zenithal projection at. While the peters projection map is superior in its portrayal of proportions and sizes, its importance goes far beyond questions of cartographic accuracy it challenges our view of the world.
Peters projection map, widely used in educational and. In order to portray the surface of a round body on a twodimensional flat plane, you must first define a developable surface i. What is a map projection map projection definition. Map projections are attempts to portray the surface of the earth or a portion of the earth on a flat surface. It can also be defined as the transformation of spherical. Learn what a map projection is, why they are used and what impact they have on maps gis systems. It is the representation of the objects and information on a curved surface in a plane using mathematical and geometric relations. About map projectionthe classification of map projection.
A map projection systematically projects locations from the surface of a spheroid to representative positions on a flat surface using mathematical algorithms. A map projection by itself isnt enough to define a projected coordinate system. The study of map projections is the characterization of these distortions. It is the only projection that can accurately represent both areas and true direction from the center of the projection. Map projections may be defined in idl direct graphics. Map projections are introduced on pages 1012, and pages. The stereographic map projection is another ancient projection, dating back to the second century b.
Map makers attempt to transfer the eartha round, spherical globeto flat paper. The shape of the earth and the geodetic datum concept are covered on pages 46. The mapmaker must select the one best suited to the needs, reducing distortion of the most important features. Angles, areas, directions, shapes, and distances can become distorted when transformed from a curved surface to a plane. These projections are called secant conic projections and are defined by two standard parallels. Type of projection cylindrical in standard presentation, these map regularlyspaced meridians to equally spaced vertical lines, and parallels to horizontal lines. Homolographic projection definition of homolographic. The mercator projection was developed by gerardus mercator flemish in 1569. And so when a map projection or when we use map projection, will always have distortion of the shape, the area, the distance, and direction. Page 79 discuss map scale and the basics of coordinate systems. Conceptual model of a lambert conformal conic map projection left and the resulting map right. Define the spatial relationship between locations on earth and their relative locations on a flat map. 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. These angular relationships are more commonly known as great circle arcs or geodesic arcs.
Other measurement system properties such as a spheroid of reference, a datum, and projection parameters like one or more standard parallels, a central meridian, and possible. As soon as humans figured out that the world is round, not flat, map making got a lot more complicated. 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. This is a summary of map projections that have articles of their own on wikipedia or that are otherwise notable. Projection meaning in the cambridge english dictionary. Extent of the map is defined by orbit of the satellite. Mercator projection is an example of cylindrical projection which became a standard map projection because of its ability to represent lines of steady course. Aug 06, 2019 the albers projection is an example of a conic map projection. The stereographic map projection is most useful for maps of polar regions for navigation purposes or large continentsized areas of similar extent in all directions. A sphere, unlike a polyhedron, cone, or cylinder, cannot be reformed into a plane. It looks similar to the widely used robinson projection, but unlike the robinson projection, retains. The earths surface projected on a map wrapped around the globe as a cylinder produces the cylindrical map projection. Map projections are the different techniques used by cartographers for presenting a round globe on a flat. It is also possible to define a secant projection by one standard.
Because earth has a curving, notquite sphericial shape, planar maps of all but the smallest areas contain significant geometric distortions of shapes, areas, distances, or. Feb 29, 2008 the three classes of map projections are cylindrical, conical and azimuthal. Introduction to map projections although earth images and map data that you use are typically rendered onto flat surfaces such as your computer screen or a sheet of paper, the earths surface obviously is not flat. Transformation from the earth surface to a flat surface always involves. Pseudocylindrical in standard presentation, these map the central meridian and parallels as straight lines. The definition of the map projection for projected coordinate systems. The problem with projections is that they change the surface in some way. The two thick red lines marking the intersections of the globe and the projection surface the cone correspond with two standard parallels on the map. Mercator projection, a map projection introduced by flemish cartographer gerardus mercator in 1569.
The peters map, the work of the german historian arno peters, provides a helpful corrective to the distortions of traditional maps. The mercator projection is a useful navigation tool, as a straight line on a mercator map indicates a straight course, but it is not a practical world map, because of distortion of scale near the poles. You can state that a dataset is in transverse mercator, but thats not enough. Like the stereographic projection and gnomonic projection, orthographic projection is a perspective or azimuthal projection, in which the sphere is projected onto a tangent plane or secant plane. Map projections are the different techniques used by cartographers for presenting a round globe on a flat surface. This booklet provides a conceptual introduction to map projections and geographic reference systems. A map projection is used to portray all or part of the round earth on a flat. The main features of azimuthal map projections are straight meridian lines, radiating out from a central. Map projections a map projection is used to portray all or part of the round earth on a flat surface. So, no direction can preserve all these properties. The world is a threedimensional sphere, but a map is a twodimensional. Direction and shape are good at the equator to about latitude 40 44 n and s. The first step in projecting from one surface to another is creating one or more points of contact.
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