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. It can also be defined as the transformation of spherical network of parallels and meridians on a plane surface. Understanding map projections landing page for kartoweb. 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. Jan 06, 2017 learn what a map projection is, why they are used and what impact they have on maps gis systems.
For example, map for example, map projections that preserve angles at a point are known as conformal, i. A map projection is a geometric function that transforms the earths curved, ellipsoidal surface onto a flat, 2dimensional plane. Every projection has its own set of advantages and disadvantages. Distortion in size and area near the projection limit appears more realistic than almost any other projection, except the vertical nearside perspective. Imagine a map projection as an attempt to reconstruct your face in two dimensions. We often talk about map projections in terms of the ways in which they distort or preserve certain things about the earth, which we call projection properties. A text entry field allows a map scale factor to be entered. Projections which preserve areas are called equivalent or equalarea projections. 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.
Each projection preserves, compromises, or approximates basic metric properties in different ways. This pdf file lists map projections supported in arcgis desktop version 10. Depending on the purpose of the map, some distortions are acceptable and others are not. The lambert azimuthal equalarea projection is mathematically based on a plane tangent to the earth. If it is tangential to a point between the pole and the equator, it is called the oblique projection. Transverse mercator is a transverse cylindric projection. The map projection is classified depending on the type of projection surface on which the globe is projected conceptually. The meridians are equally spaced parallel vertical lines, and the parallels of latitude are parallel horizontal straight lines that are spaced farther and farther apart as their distance from the equator increases.
About map projectionthe classification of map projection. The mapmaker must select the one best suited to the needs, reducing distortion of the most important features. 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. The title string has a carriagereturn font positioning code appended. It is often described as a cylindrical projection, but it must be derived mathematically. A map is a projection of data usually from the real earth. If the graticule of latitude and longitude are projected onto the cylinder and the cylinder unwrapped, then a gridlike pattern of straight lines of latitude and longitude would result. Are mathematical expressions which transform the spherical earth to a flat map. Pdf in this paper, we introduce some known map projections from a.
These include a title, scale, legend, date of publication, direction, borders, and information about the map projection. Indeed it would be beyond the abilities of todays geospatial professionals to produce a map projection without a computer. Map projections explained a beginners guide youtube. The subsections below describe the stereographic projection properties. The earths surface projected on a map wrapped around the globe as a cylinder produces the cylindrical map projection. Additional detailed information about these projections is available at the links entitled supported map projections. It is, unfortunately, impossible to have all these properties together in one map projection. A transverse projection has its main orientation perpendicular to the earths axis. The stereographic projection was known to hipparchus, ptolemy and probably earlier to the egyptians. Projected on a map formed into a cone gives a conical map projection. We will taker a closer look at the popular mercator projection and examine how the projection.
Mapprojection map projection is the method of transferring the graticule of latitude and longitude on a plane surface. This results in effects known as a little planet when the center of projection is the nadir and a tube when the center of projection is the zenith. The purpose of the map determines which projection should form the base for the map. Typically calculated from formula, and not based on a particular projection polyhedral maps polyhedral maps can be folded up into a polyhedral approximation to the sphere, using particular projection to map each face with low distortion.
No map projection can preserve shapes of larger regions. A map projection is the mathematical transformation of coordinates on one surface, in our case the ellipsoidal reference surface of the earth, to coordinates on the projection plane. It is a visual representation of an area a symbolic depiction. An equivalent map projection, also known as an equalarea map projection, correctly represents areas sizes of the sphere on the map. This projection is best suited for northsouth oriented areas. There is some info about projections, but more importantly, its about their appearance. Equalarea projections a map projection is equal area if every part, as well as the whole, has the same area as the corresponding part on earth, at the same reduced scale. 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. This is not because a sufficiently clever projection has yet to be devised. The transverse mercator projection is shown centered on greenwich.
Learn what a map projection is, why they are used and what impact they have on maps gis systems. This booklet provides a conceptual introduction to map projections and geographic reference systems. Select a suitable map projection or coordinate system. Out of more than 200 different map projections images you can select two at a time to view their. No projection can retain more than one of these properties over a large portion of the earth. It is the only projection that can accurately represent both areas and true direction from the center of the projection. The stereographic map projection is another ancient projection, dating back to the second century b.
There are many properties that might be relevant to all sorts of questions but there are two major properties that we will consider here. As you know that, the earth on which we live in is not flat. Apr 25, 2017 the map projection is classified depending on the type of projection surface on which the globe is projected conceptually. The eckert iv map projection properties of maps when considering what map to use for a particular purpose, you need to know what type of properties the map has. This gives the illusion of a threedimensional globe. Converting a sphere to a flat surface results in distortion. Map projections are the different techniques used by cartographers for presenting a round globe on a flat surface. During such transformation, the angular geographic coordinates latitude, longitude referencing positions on the surface of the earth are converted to cartesian coordinates x, y. This site ist about map projections, specifically about world map projections.
Form some projections distort the form of features e. The three possible apects of a map projection are normal, transverse and oblique. This booklet provides a conceptual introduction to. 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. A sphere is based on a circle, while a spheroid or. Feb 29, 2008 the three classes of map projections are cylindrical, conical and azimuthal. One of its most important uses was the representation of celestial charts. We have also seen in class that for a bounded linear map p.
Scale increases perpendicular to the radii toward the periphery. A menu bar at the top allows configuration of application properties. The term planisphere is still used to refer to such charts. Map makers attempt to transfer the eartha round, spherical globeto flat paper. Other geographical properties vary according to the specific projection.
This is the most profound single fact about map projectionsthey distort the worlda fact that you will investigate in more detail in module 4, understanding and controlling distortion. For example, in the map propertiescoordinate systems window select. The stereographic projection is available in arcgis pro 1. A cylindrical projection can be imagined in its simplest form as a cylinder that has been wrapped around a globe at the equator. Map projections and distortion city university of new york. Planar perspective projection, viewed from infinity. A map projection is needed to show the spherical surface of the earth on a flat map see whats a map projection. Different projections have been designed where the distortion in one property is minimized, while other properties become more distorted. Some map projections preserve none of the properties described above, but instead seek a compromise that minimizes distortion of all kinds. Vice versa, an areapreserving projection can not be conformal, resulting in shapes and bearings distorted in most places of the map. The universal transverse mercator utm coordinate system and gausskruger coordinate systems are based on the transverse mercator projection and the state plane coordinate system uses it for all northsouth zones. However, to maintain accuracy for largerscale maps scales of 1.
All map projections distort the surface in some fashion. The stereographic map projection is conformal but not. When this type of projection is used for smallscale maps showing large regions, the distortion of angles and shapes is. The albers projection is an example of a conic map projection. A map projection is a systematic transformation of the latitudes and longitudes of positions on the surface of the earth to a. Which lines these are depends on the projection and even on particular settings within a projection. A map projection either preserves areas everywhere, or distorts it everywhere. 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.
Elements of map projection with applications to map and chart construction by deetz, charles henry, 1864. Usgs topographic map based on the transverse mercator projection is nearly correct in every respect. Aug 06, 2019 the albers projection is an example of a conic map projection. 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. In order to portray the surface of a round body on a twodimensional flat plane, you must first define a developable surface i. Despite the impossibility of maintaining consistent linear scale on a map projection, there are two other properties that may be maintained, though not both on the same projection. When, at every point on the map, maximum linear scale distortion is compensated by opposite distortion in the opposite direction, area scale is maintained. The central meridian and antimeridian lines are presented as one vertical line in the middle of the projection. With the exception of mental maps, all maps share common properties or map basics that provide information to assist the reader in studying and interpreting the map. Nov 14, 2019 this pdf file lists map projections supported in arcgis desktop version 10. Introduction a map is a representation of all or part of the earth drawn on a flat surface at a specific scale. The definition of the map projection for projected coordinate systems. 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.
A scrolling list allows a map projection to be chosen. As mentioned above, the correctness of area, shape, direction and distances are the four major global properties to be. This perspective projection views the globe from an infinite distance. The stated scale of a map is true for certain lines only. Transverse mercatorproperties of maps documentation. Mathematics and computers are the indispensable allies of map projection. Additional detailed information about these projections is. Three horizontal sliders allow the projection center and rotation to be changed. Mercator projection, a map projection introduced by flemish cartographer gerardus mercator in 1569. The subsections below describe the transverse mercator projection properties. Five essential characteristic properties of map projections are subject to distortion.
C to leave room for grid labels along the top of the projection border. A map projection is the transformation of earths curved surface or a portion of onto a twodimensional flat surface by means of mathematical equations. Between those scales, choosing to use a sphere or spheroid will depend on the maps purpose and the accuracy of the data. The example shown above is the polyconic projection, where parallels are all nonconcentric circular arcs, except for a straight equator, and the centers of these circles lie along a central axis. A map projection is used to portray all or part of the round earth on a flat surface. Orthographic projection an overview sciencedirect topics. Mercator projection, type of map projection introduced in 1569 by gerardus mercator. There are several map projections which preserve some of the properties of the sphere at the expense of others. A sphere, unlike a polyhedron, cone, or cylinder, cannot be reformed into a plane. This process is typically, but not necessarily, a mathematical procedure some methods are graphically based.
A graphics window displays the name of the currently selected. This centering minimizes distortion of all properties in that region. The stereographic map projection is shown centered on the south pole. Angles, areas, directions, shapes, and distances can become distorted when transformed from a curved surface to a plane. Planisphaerium by ptolemy is the oldest surviving document that describes it. We will taker a closer look at the popular mercator projection and examine how the. It was originally known as the planisphere projection. Pdf properties of projections roshan senaratne academia. In a normal projection, the main orientation of the projection surface is parallel to the earths axis as in the second figure below. The three classes of map projections are cylindrical, conical and azimuthal. Projected coordinate system continental north america nad832011 contiguous usa albers on hitting ok, the properties window should disappear, and the counties change shape and orientation a bit, from.
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