A brief look at map projections views of the world. In all the map projections we will be dealing with, the datum surface is a 3dimensional surface, either a sphere or ellipsoid, representing the earth. Armed forces military maps show the earth drawn to scale as you would see it from above the military uses the universal transverse mercator utm and the universal polar stereographic ups grid system. All meridians are straight lines merging at the pole. In cartography, a map projection is a way to flatten a globes surface into a plane in order to make a map. To avoid having negative coordinates, false easting and false northing are used in gis. Cylindrical wrap a piece of paper around the earth to form a cylinder that touches the equater all the way around the earth. A map projection systematically projects locations from the surface of a spheroid to representative positions on a flat surface using mathematical algorithms. This projection is perhaps the most famous of the cylindrical map projections. Page 79 discuss map scale and the basics of coordinate systems. Map projection is the method of transferring the graticule of latitude and longitude on a plane. Although the earth is best represented by a spheroid, the earth is sometimes treated as a sphere.
However, map projections have distortions which depend largely on the size of the area being mapped. In this paper, we introduce some known map projections from a model of the earth to a flat sheet of paper or map and derive the plotting equations for these projections. To create a flat representation of earths curved surface something has to give. Some data visualization types are difficult to interpret.
Although the earth is best represented by a spheroid. Map projectionspdf versions of numerous projections, created. How to build a merger model a basic overview of the key. This is the concept behind the construction of a map projection. The process of projection involves distorition of area, distance, shape, and angles. Types of map projections portland state university. Name date comparing map projections to the globe analyze the maps on the map projections handout and a globe to complete the charts below. A world map that isnt quite right when it comes to any individual criteria, but isnt as terribly wrong in any of them, either, as other formulae used to create projections. A map projection is the mathematical transformation of coordinates on a. Each and every map represents a distorted view of reality. Interactive map projections and distortion uc santa barbara. Scale changes in one direction to be offset by scale changes in the other direction. Name date map projections analyze the three map projections.
This requires a systematic transformation of the latitudes and longitudes of locations from the surface of the globe into locations on a plane. 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. Map projections are created for certain purposes and should be used for those purposes. He may actually believe that all map projections are in a way bad. Except where otherwise noted, images on this site are by tobias jung and are licensed under cc bysa 4. This could be inferred from the fact that he much later began publishing a series of bad map projections, starting with 1784. On a map of the united states, distortion may affect careful long distance measurements but is of little concern to nontechnical users.
Therefore, cartograms are not as unusual as they might appear at a first glance. The process of converting a threedimensional space to a twodimensional map is called projection. Central line the center origin of a map projection. An example would be the takeover of one printing firm by another.
Composite map projections combine several projections that are. Adaptive composite map projections cartography and. There are various techniques for creating new map projections from existing pro. This booklet provides a conceptual introduction to map projections and geographic reference systems. The three main families of map projections most map projections can be categorized into three families based on the cylinder, cone, and plane geometric shapes. The state grids have been merged into countrywide grids. There are three types of developable1 surfaces onto which most of the map. 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. In cartography, a map projection is a way to flatten a globes surface into a plane in order to.
Types of map projections city university of new york. Most of these types of projections distort shape in the polar regions more than at the equator. Although a map projection gets its name from the idea of projecting a globe onto a flat surface, map projections are actually created using mathematical formulas. In this guide, well outline the acquisition process from start to finish, the various types of.
Map projections are a central aspect of the worldmapper project because the maps respectively cartograms featured in the project are basically not different from some sort of reprojection of the world, albeit in a different way than conventional. Map projections are influenced and constrained by five characteristic properties. Bibliography of map projections editors of first edition. Planar, azimuthal or zenithal projection conic projection cylindrical projection mathematical or conventional projection. Snyder, 1987 an album of map projections usgs pp 1453, j. The following formulas combine these steps in a form which may be. Conceptually, there are three types of surfaces that a map can be projected onto. Pay attention to the lines of longitude and any distortion. Equivalent or equal area projections a map areaof a given size, a circle three inches in diameter for instance, represents same amount of earth space no matter where on the globe the map area is located. Pdf, 1997 cegis map projection bibliography usgs, database, 2011 map projections a working manual usgs pp 95, j. The earth exists in threedimensions but, other than globes, most representations of the earth are two dimensional. Map projections used by the us geological survey usgs. Scale distortions on maps are shown on the map by an ellipse of distortion or using scale factor which is the ratio of the scale at a given point to the true scale.
There are two common types of coordinate systems used in gis. Learn how mergers and acquisitions and deals are completed. In the end each and every map projection has a place, and there is no limit to the amount of projections that can be created. The shape of the earth and the geodetic datum concept are covered on pages 46. Maps and map reading are essential skills that all of the armed forces need.
The definition of the map projection for projected coordinate systems. The importance of map projections by sarah lyle on prezi. Types of map projections the number of map projections made possible is limitless, and hundreds have been published. It differs from other types of cylindrical projections in that it is conformal. Because maps are flat, some of the simplest projections are made onto geometric shapes that can be flattened without stretching their surfaces. Because there is no limit to the number of possible map projections, there can be no comprehensive list. Ppt chapter 2 map projection powerpoint presentation. Tobler university of california santa barbara, usa since the time of ptolemy 2000 years ago the objective of map projections has been to produce maps of high metric fidelity, and this is still the prime objective today. This is a summary of map projections that have articles of their own on wikipedia or that are otherwise notable. Part or all of this report is presented in portable document format pdf. In horizontal mergers one corporation acquires another corporation whose product or service is closely related or of the same type nahavandi and malekzadeh 1993, 27. All projections of a sphere on a plane necessarily distort the surface in some way and to some extent. Types of map projections many types of map projections are being used for map making. Geological survey bulletin 1856, 1997 also two online editions installed at ohio state university, 1994, 1996 under supervision of eric john miller and duane f.
When mapping a small area, distortion is negligible. Snyderand harry steward editor of revisions 1st edition. Pdf cartographers have developed various techniques for deriving new. Some common examples are cones, cylinders, and planes.
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