The map is thereby conformal. The Mercator projection has been used extensively for world maps im which the distortion towards the polar regions grows rather large, thus incorrectly Map Projections Geradus Mercator invented his famous projection in 1569 as an aid to navigators. If there is no such scale then the ruler distances between the end points and the equator, y1 and y2, give the result via an inverse formula: These formulæ give rhumb distances on the sphere which may differ greatly from true distances whose determination requires more sophisticated calculations. In this case the maximum latitude attained must correspond to y = ±W/2, or equivalently y/R = π. [16][19][e] For the Mercator projection, h = k, so the ellipses degenerate into circles with radius proportional to the value of the scale factor for that latitude. Oh yes, I did. It became the standard map projection for nautical purposes because of its ability to represent lines of constant course, known as rhumb lines or loxodromes, as straight segments that conserve the angles with the meridians. English-Estonian dictionary. Mercator, Projection de: Source file : RAMEAU: see also : Gerard Mercator (1512-1594) Field : Géographie: Variant subject headings : Mercator, Représentation de Projection de Mercator Représentation cylindrique conforme directe Représentation de Mercator: related to this theme (1 resources in data.bnf.fr) More general example of Tissot's indicatrix: the, Fisher, Irving (1943). 1989. If α is neither 0 nor π then the above figure of the infinitesimal elements shows that the length of an infinitesimal rhumb line on the sphere between latitudes φ; and φ + δφ is a sec α δφ. Mercator projection, type of map projection introduced in 1569 by Gerardus Mercator.It is often described as a cylindrical projection, but it must be derived mathematically.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. It is less practical for world maps, however, because the scale is distorted; areas farther away from the Equator appear disproportionately large. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. Specified in [square brackets]: Actual size of the projection (minus the black or white background). For a ruler measurement of a short line, with midpoint at latitude φ, where the scale factor is k = sec φ = 1/cos φ: With radius and great circle circumference equal to 6,371 km and 40,030 km respectively an RF of 1/300M, for which R = 2.12 cm and W = 13.34 cm, implies that a ruler measurement of 3 mm. projection.] Mercator or cylindrical map projection The Mercator projection is a cylindrical map projection presented by the Flemish geographer and cartographer Gerardus Mercator in 1569. Map Projections. Autor: Dr. Josep Maria Rabella. It became the standard map projection for nautical purposes because of its ability to represent lines of constant course, known as rhumb lines or loxodromes, as straight segments. The scale on the equator is 0.99; the scale is k = 1 at a latitude of approximately ±8° (the value of φ1); the scale is k = 1.01 at a latitude of approximately ±11.4°. projection cylindrique oblique. Scegli tra immagini premium su Mercator Projection della migliore qualità. For example, on a map with R = 1 the values of y = 0, 1, 2, 3 correspond to latitudes of φ = 0°, 50°, 75°, 84° and therefore the successive intervals of 1 cm on the map correspond to latitude intervals on the globe of 50°, 25°, 9° and distances of 5,560 km, 2,780 km, and 1,000 km on the Earth. Les coordonnées des contours résultent d'une simple conversion sur un plan des coordonnées géodésiques. Since α is constant on the rhumb this expression can be integrated to give, for finite rhumb lines on the Earth: Once again, if Δφ may be read directly from an accurate latitude scale on the map, then the rhumb distance between map points with latitudes φ1 and φ2 is given by the above. La projection de Mercator est une représentation plane de la Terre de type cylindrique. [1913 Webster] 1. A straight line on the Mercator map at angle α to the meridians is a rhumb line. Being a cylindrical projection, the deformation experienced by the areas closest to the poles is such that Greenland (2,166,086 km²) is similar in extent to Africa (30,221,535 km²), when the actual data show that comparing both territories is simply crazy. Similar phrases in dictionary English French. When the Earth is modelled by a spheroid (ellipsoid of revolution) the Mercator projection must be modified if it is to remain conformal. The Mercator projection was developed in 1569 by Gerardus Mercator as a navigational tool. It is often described as a cylindrical projection, but it must be derived mathematically. Longer distances require various approaches. Much Web-based mapping uses a zoomable version of the Mercator projection with an aspect ratio of one. When the Portuguese, under the leadership of Prince Henry the Navigator, ventured farther south along the west coast of Africa, they encountered navigational difficulties by assuming that the charts used in the Mediterranean could simply be extended. Interpretación Traducción Article 4 : Le système de coordonnées planimétriques est constitué d’un référentiel géodésique et d’une ... - La Projection cartographique BFTM (projection cylindrique transverse de Mercator) ; Similarly sec 2.56° = 1.001, so a strip of width 5.12° (centred on the equator) is accurate to within 0.1% or 1 part in 1,000. The Mercator projection is a cylindrical map projection presented by the Flemish geographer and cartographer Gerardus Mercator in 1569. Below is what it looked like: The difference is 3,338 km so the ruler distance measured from the map is quite misleading even after correcting for the latitude variation of the scale factor. The length of the chord AB is 2(a cos φ) sin λ/2. On a Mercator projection, for example, the landmass of Greenland appears to be greater than that of the continent of South America; in actual area, Greenland is smaller than the Arabian Peninsula. [1913 Webster] 2. A meridian of the map is a great circle on the globe but the continuous scale variation means ruler measurement alone cannot yield the true distance between distant points on the meridian. Our editors will review what you’ve submitted and determine whether to revise the article. Scopri le migliori foto stock e immagini editoriali di attualità di Mercator Projection su Getty Images. Even more extreme truncations have been used: a Finnish school atlas was truncated at approximately 76°N and 56°S, an aspect ratio of 1.97. The property of the Mercator projection map that made it useful to navigators is that it preserves angles. The graph shows the variation of the scale factor with latitude. 3:12. Therefore, the Mercator projection is adequate for mapping countries close to the equator. This chord subtends an angle at the centre equal to 2arcsin(cos φ sin λ/2) and the great circle distance between A and B is 2a arcsin(cos φ sin λ/2).) The difference is small for short distances but increases as λ, the longitudinal separation, increases. F. The scale factor is unity on the equator, as it must be since the cylinder is tangential to the ellipsoid at the equator. This map's grid is rectangular and lines of latitude and longitude are parallel throughout. He even quantifies his statement: "When the great circle distances which are to be measured in the vicinity of the equator do not exceed 20 degrees of a great circle, or 15 degrees near Spain and France, or 8 and even 10 degrees in northern parts it is convenient to use rhumb line distances". Converting ruler distance on the Mercator map into true (great circle) distance on the sphere is straightforward along the equator but nowhere else. Therefore, by construction, the Mercator projection is perfectly accurate, k = 1, along the equator and nowhere else. On the other hand, the geodesic between these points is a great circle arc through the pole subtending an angle of 60° at the center: the length of this arc is one sixth of the great circle circumference, about 6,672 km. Only accurate Mercator projections of regions near the equator will necessitate the ellipsoidal corrections. The ordinate y of the Mercator projection becomes infinite at the poles and the map must be truncated at some latitude less than ninety degrees. Cartography of Belgium (history of surveying and creation of maps of, Cartography of the Low Countries (history of surveying and creation of maps of the, This page was last edited on 8 December 2020, at 06:18. Najboljši sosed: prodajna mesta, akcije, ugodnosti, novice, dogodki, recepti in mnogo več. [1913… This is not the shortest distance between the chosen endpoints on the parallel because a parallel is not a great circle. [18] This section discusses only the last of these cases. In fact, the Mercator projection was the first projection regularly identified in atlases. The result is that deviation of the scale from unity is reduced over a wider range of latitudes. The classic way of showing the distortion inherent in a projection is to use Tissot's indicatrix. This article was most recently revised and updated by, https://www.britannica.com/science/Mercator-projection. If the latitudes of the end points cannot be determined with confidence then they can be found instead by calculation on the ruler distance. Over long distances the rhumb lines…, …the result was the now-familiar Mercator map shown in the photograph.…. Nicolas Tissot noted that the scale factors at a point on a map projection, specified by the numbers h and k, define an ellipse at that point. For two points, A and B, separated by 10° of longitude on the parallel at 60° the distance along the parallel is approximately 0.5 km greater than the great circle distance. Erläuterung Übersetzung English-Spanish dictionary of Geography . Working from the projected map requires the scale factor in terms of the Mercator ordinate y (unless the map is provided with an explicit latitude scale). For example, the basic transformation equations become. This is a standard technique of extending the region over which a map projection has a given accuracy. a map projection of the earth onto a cylinder; areas appear greater the farther they are from the equator It is a cylindrical map projection that is a product of its time. However, if the map is marked with an accurate and finely spaced latitude scale from which the latitude may be read directly—as is the case for the Mercator 1569 world map (sheets 3, 9, 15) and all subsequent nautical charts—the meridian distance between two latitudes φ1 and φ2 is simply. geography in cartography, any of numerous map projections of the terrestrial sphere on the surface of a cylinder that is then unrolled as a plane. English-German geography dictionary . For cylindrical projections, the axes of the ellipse are aligned to the meridians and parallels. The Mercator projection is a transformation of a cylindrical projection used for navigation. Mercator. [18], The above formulae are written in terms of the globe radius R. It is often convenient to work directly with the map width W = 2πR. Updates? Today, the use of the Mercator projection is not justified except by specific interests. On any other parallel the scale factor is sec φ so that. - Les déformations cartographiques - Projection cylindrique, conique, azimutale - Carte Mercator, Peters Erratum : dia 18 - nous sommes "proches" / dia 18 et 19 : territoires et non pays. Mercator projection translation in English-French dictionary. The projection of Mercator is a cylindrical cartographic projection that represents the whole terrestrial surface. His name is a latinized version of Gerhard Kramer. The ellipsoidal correction of the scale factor increases with latitude but it is never greater than e2, a correction of less than 1%. (See Legend 12 on the 1569 map.) So my first recommendation is: Verify if you reallyneed a rectangular map or if a different shape might fit the purpose of the map better. This need not be done symmetrically. For Greenland, taking 73° as a median latitude, hk = 11.7. The distinction between rhumb (sailing) distance and great circle (true) distance was clearly understood by Mercator. Abigail Alkire 48,509 views. See the discussion on distance formulae below. Image of: Mercator. When α = 0 or π it corresponds to a meridian great circle (if continued around the Earth). Since ruler measurements can furnish the map ordinate y and also the width W of the map then y/R = 2πy/W and the scale factor is determined using one of the alternative forms for the forms of the inverse transformation: The variation with latitude is sometimes indicated by multiple bar scales as shown below and, for example, on a Finnish school atlas. American Cartographer. Projection Pro*jec tion, n. [L. projectio: cf. The aspect ratio of his map is 198/120 = 1.65. English: The Mercator projection is a cylindrical map projection presented by the Flemish geographer and cartographer Gerardus Mercator in 1569. /mɜˌkeɪtəz prəˈdʒɛkʃən/ (say mer.kaytuhz pruh jekshuhn) noun a map projection with rectangular grid which is conformal and on which any rhumb line is represented as a straight line. (The value of e2 is about 0.006 for all reference ellipsoids.) Omissions? In the extreme case where the longitudinal separation is 180°, the distance along the parallel is one half of the circumference of that parallel; i.e., 10,007.5 km. For all other values it is a spiral from pole to pole on the globe intersecting all meridians at the same angle, and is thus not a great circle. When α = π/2 or 3π/2 the rhumb corresponds to one of the parallels; only one, the equator, is a great circle. Corrections? cylindrical projection 圆柱投影. "A World Map on a Regular Icosahedron by Gnomonic Projection.". It was developed by Gerardus Mercator in the sixteenth century, in the year 1569. A generator of a cylinder is a straight line on the surface parallel to the axis of the cylinder. The northern inflation acutely distorts Russia's shape as well, making it appear much taller north-to-south and greatly stretching its arctic regions compared to its mid latitudes. Did I mention that I’m not a big fan of cylindric projections? in any direction from a point on the equator corresponds to approximately 900 km. 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. Narrower strips are better: sec 8° = 1.01, so a strip of width 16° (centred on the equator) is accurate to within 1% or 1 part in 100. One problem is the variation of scale with latitude, and another is that straight lines on the map (rhumb lines), other than the meridians or the equator, do not correspond to great circles. projection de Mercator transverse [ projection cylindrique conforme de Lambert | projection de Gauss | projection de Mercator transversale ] The area scale factor is the product of the parallel and meridian scales hk = sec2φ. Elles correspondent donc à une projection cylindrique équidistante. Often, it is innocent of the crimes it is accused of, and I want to address this as well as what it actually is guilty of. Universitat de Barcelona Promotor: Institut Cartogràfic de Catalunya, 2013. sinònims complementaris: projecció cilíndrica conforme de Mercator, projecció conforme de Mercator, planisferi de Mercator, mapa de Mercator cs proyección de Mercator; fr projection cylindrique; it proiezione cilindrica; en cylindrical projection; de zylindrische Abbildung Le choix d'une projection et la conversion d'une projection à une autre comptent parmi les difficulté que les cartographes ont du … For the above model 1 cm corresponds to 1,500 km at a latitude of 60°. The interpretation of such bar scales is non-trivial. [17], There are many alternative expressions for y(φ), all derived by elementary manipulations. The corresponding distances for latitudes 20°, 40°, 60° and 80° are 846 km, 689 km, 450 km and 156 km respectively. gd−1(φ). The act of throwing or shooting forward. It became the standard map projection for navigation because it is unique in representing north as up and south as down everywhere while preserving local directions and shapes. cylindrical projection. This projection is widely used for navigation charts, because any straight line on a Mercator projection map is a line of constant true bearing that enables a navigator to plot a straight-line course. This is his famous world map of 1569. The Mercator Projection is frequently used as a scapegoat by people who are surprised by certain geographical facts, mostly relating to distance or area. Without a doubt, the most famous map projection is the Mercator projection. It is particularly useful for navigation, though the scale… cylindrical projection. The scale is now true at these latitudes whereas parallels between these latitudes are contracted by the projection and their scale factor must be less than one.