The three main families of map projections unwrapping the sphere to a plane. 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. This requires a systematic transformation of the latitudes and longitudes of locations from the surface of the globe into locations on a plane. Planar projections project map data onto a flat surface touching the globe.
Zenithal projections also known as azimuthal projections are a class of projections in which the surface of projection is a plane. Map projection map projection is the method of transferring the graticule of. Also called azimuthal or zenithal can be any aspect. Download ncert solutions class 11 geography chapter 4 map projections free, ncert solutions for class 11 geography for chapter 4 map projectionsexercise1. The three classes of map projections are cylindrical, conical and azimuthal. A map projection is a way to flatten a globe s surface into a plane in order to make a map. Zenithal map projections part 2 some properties of the five projections by keith selkirk, school of education, university of nottingham introduction in the first article, five polar zenithal map projections were described. A great variety of map projections has been devised to provide for the various properties that may be desired in maps. Zenithal projection definition of zenithal projection by.
The euler angles for constructing oblique forms of these projections are specified in the same way as for the cylindrical projections, i. Some projections have equalarea properties, while others provide for conformal delineations in which, for small areas, the shape is. Map projections page 3 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. Planar projection azimuthal or zenithal in planar also known as azimuthal or zenithal projections, the reference spherical surface is projected onto a plane.
Map projections chapter 4 map projections what is map projection. We will taker a closer look at the popular mercator projection and examine how the projection. In them the map is assumed to touch the earth at the north pole. The native coordinate system is such that the polar axis is orthogonal to the plane of projection, whence the meridians are projected as equispaced rays emanating from a central point, and the parallels are mapped as concentric. This map projection is practical for nautical applications due to its ability to represent lines of constant course, known as rhumb lines, as straight segments that conserve the angles with the meridians. This type of projection is mostly used by the united states geological surveyusgs. Choose the right answer from the four alternatives given below.
The meridians are uniformly divided so as to give uniformly spaced parallels. Stereographic polar zenithal projection slideshare. Coordinate systems, projections, and transformations an overview. In this chapter, we will seek the answers of such essential questions. For example, the national atlas of the us uses a lambert azimuthal equalarea projection to display information in the online map maker application, and the european environment agency recommends its usage for european mapping for statistical analysis and display. Feb 29, 2008 the three classes of map projections are cylindrical, conical and azimuthal. Map projections mathematical conversion of 3d earth to a 2d surface longitude latitude to x, y. These maps are useful for navigation if the map reader knows how. Twopoint azimuthal shows correct azimuths but not distances from either of two points to any other point. When projected on a planar map it produces an azimuthal or zenithal map projections. A map projection without distortions would correctly represent shapes, angles. A light at the centre of the earth then casts a shadow of the earths surface on the plane map.
Zenithal projection definition and meaning collins. A map is a projection of data usually from the real earth. It is carried out by an orderly and systematic representation of the parallels of latitude and the meridians of longitude of the spherical earth or part of it on a plane surface on a conveniently chosen scale. In zenithal projection, direction is correct in all sides from the centre of the map. The earths surface projected on a map wrapped around the globe as a cylinder produces the cylindrical map projection. Zenithal projection definition at, a free online dictionary with pronunciation, synonyms and translation. A useful application for this type of projection is a polar. Nov 22, 2018 above video explains you the concept of gnomonic polar zenithal projection. Pdf a classification of map projections 1 waldo tobler. If it is tangential to a point between the pole and the equator, it is called the oblique projection. Conventional projections are puremathematical constructions designed to map the entire sphere with minimal distortion. Three large families of map projection, plus several smaller ones, are generally acknowledged. Copies of these textbooks may be downloaded and used as textbooks or for reference.
Map projections explained a beginners guide youtube. Types of map projections the number of map projections made possible is limitless, and hundreds have been published. A projection of the graticule of the reduced earth onto a plane placed tangential to the reduced earth at a point. The lambert azimuthal projection is used as a map projection in cartography. When using a plane projection the surveyor must be aware of the distortion that occurs as a result of using the projection. Zenithal projection definition of zenithal projection at. Which projection is most suitably used for which area. Thus the word projection may be used literally, and. The gnomonic map projection in the image is centered on the north pole with meridians radiating out as straight lines. Merit and demerits of polar zenithal map projection. The mercator projection is a cylindrical map projection presented by the flemish geographer and cartographer gerardus mercator in 1569. Jan 06, 2017 learn what a map projection is, why they are used and what impact they have on maps gis systems. In the second instance of projection, an equal area map is shown. All projections of a sphere on a plane necessarily distort the surface in some way and to some extent.
Mapmakers have developed hundreds of map projections, over several thousand years. Types of map projections based on developable surface. The figure below shows the surfaces involved in these three classes of projections. Zenithal projection meaning of zenithal projection by lexico. Williamolssons projection combines the lambert azimuthal equalarea with a modified werner. Ncert solutions class 11 geography chapter 4 map projections. Mercator projection an overview sciencedirect topics. This booklet provides a conceptual introduction to map projections and geographic reference systems. Every projection has its own set of advantages and disadvantages. Zenithal definition is of, relating to, or located at or near the zenith. In stereographic projections, the perspective point is located on the surface of globe directly opposite from the point of tangency of the plane. The geoid is defined as the surface of the earths gravity field, which is approximately the same as mean sea level. Pdf a projection aspect is usually defined in references as the relation to the socalled auxiliary surface. These are the polar zenithal projections we shall examine below.
Steerss useful little book on map projections, the third edition of which has recently been issued, is written for those students of geography who have only the most elementary knowledge of. As mentioned above, the correctness of area, shape, direction and distances are the four major global properties to be. Map cartography is the method of transferring the latitude and longitude lines of the globe to the plane paper under cartography. Directions from a central point to all other points are maintained accurately in azimuthal projections also known as zenithal or truedirection projections. As the age of exploration reached new heights and there was a need for an accurate map of the world, cartographers struggled with the challenge of.
A tutorial description of the general usage of the cartographic projection program proj. The gnomonic projection is said to be the oldest map projection, developed by thales in the 6th century bc. Stereographic polar zenithal projection draw a stereographic polar zenithal projection for northern hemisphere on a scale 1. Spherical earth or trap the latitudelongitude coordinates produced by light or geometric methods to create a map on a flat surface with a large terrain of earth or land grid map projection map projection are called. Points close to center point show great distortion on the map. The point of tangency is projected onto the center of the plane and its latitude and longitude are the points at the center of the map projection, respectively. The gnomonic projection in the gnomonic projection the map may be considered as a plane touching the earth at the north pole. The concept of map projection yaaka digital network. Stereographic projection is a conformal projection, that is over small areas angles and therefore shapes are preserved. A map projection is a systematic transformation of the latitudes and longitudes of positions on the surface of the earth to a. This is a summary of map projections that have articles of their own on wikipedia or that are otherwise notable.
Mapthematics and geocart projections list zenithal equivalent. Zenithal projection article about zenithal projection by. It is the system of transformation of the spherical surface onto a plane surface. Zenithal projection definition and meaning collins english. An introduction to the study of map projections nature. Distortion is moderate for one hemisphere but becomes extreme for a map of the entire earth.
When projected directly onto the mapping plane it produces an azimuthal or zenithal or planar map projection. While it may have been used by ancient egyptians for star maps in some holy books, the earliest text describing the azimuthal equidistant projection is an 11thcentury work by albiruni the projection appears in many renaissance maps, and gerardus mercator used it for an inset of the north polar regions in sheet and legend 6 of his wellknown 1569 map. They are basically classified into four groups in accordance with the map projection theory or the types of surfaces that are tangent with the globe. Projected on a map formed into a cone gives a conical map projection. Coordinate systems, projections, and transformations. These projections can also be equal area, conformal or equidistant. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Mapthematics and geocart projections list zenithal. The path of the shadowtip or lightspot in a nodusbased sundial traces out the same hyperbolae formed by parallels on a gnomonic map. Depending on whether the point of tangency is the pole or the equator or some other point, they are referred to as a polar, equatorial, or oblique azimuthal projection. Notice that the basic shape of the head is held true, but the area is severely distorted. In effect, a projection is a systematic method of drawing the earths meridians and parallels on a flat surface. Map projection is the method of transferring the graticule of latitude and longitude on a plane. Refer to other chapters and books at other links ncert now providing you soft copies of all textbooks of all subjects from class first to twelfth.
Types of map projections many types of map projections are being used for map making. It is perpendicular to the direction of gravity pull. Zenithal projections definition of zenithal projections by. This projection is useful for mapping the polar regions. Azimuthal projections with azimuthal projections, the uv plane is tangent to the globe. The mapmaker must select the one best suited to the needs, reducing distortion of the most important. Other names for this projection include postel and zenithal equidistant. Zenithal projections definition of zenithal projections. About map projectionthe classification of map projection.
Understanding map projections landing page for kartoweb. A planar projection is also known as an azimuthal projection or a zenithal projection. Several cartographers used it during the sixteenth century, including guillaume postel, who used it in 1581. In the first of these articles we shall study five basic types of projection and in the second we shall look at some of the mathematics which can be developed from them. Hence in both mapping and surveying we have the problem of which projection to use and of understanding the distortions that are introduced. From a mathematical viewpoint the conventional projections. Ncert class 11 geography map projections ncert book.
Because there is no limit to the number of possible map projections, there can be no comprehensive list. Map projections a map projection is used to portray all or part of the round earth on a flat surface. Zenithal projection can also be known as azimuthal projection zenithal projection is a type of projection which uses plane as the surface of projection. Because earth has a curving, notquite sphericial shape, planar maps. Planar, azimuthal or zenithal projection this type of map projection allows a flat sheet to touch with the globe, with the light being cast from.
Stereographic polar zenithal projection practical excercise 2. This projection may have been first used by the ancient egyptians for star charts. Transformation to oblique spherical coordinates from normal spherical. Map projections of practical work in geography book chapter 4 map projections what is map projection. Oct 01, 2015 types of map projections many types of map projections are being used for map making. The first projected map is a mercator, which is a conformal map we will look at the mercator in greater detail later. The native coordinate system is such that the polar axis is orthogonal to the. The quality of the images varies depending on the quality of the originals. The azimuthal equidistant projection is an azimuthal map projection. Types of map projections geoinformatics and space technology.