The gcs tells your data where to draw on the earth, and the projection tells the map how to distort the earth onto a flat surface. Types of map projections many types of map projections are being used for map making. What is a map projection map projection definition. The definition of the map projection for projected coordinate systems. This is a summary of map projections that have articles of their own on wikipedia or that are otherwise notable. Meaning, pronunciation, translations and examples log in dictionary. We could continue adding data frames to the previous map file, but to simplify things, lets create a new map file. 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. Because there is no limit to the number of possible map projections, there can be no comprehensive list.
Projection format once you have determined the correct size of screen based upon the audience area, that size may be modified based upon the projection equipment. In the sinusoidal projections, for example, the central meridian and all parallels are their true lengths. A map projection in which angles on the curved earth are preserved after being projected to a plane is called a conformal projection. Without maths and computers, teaching map projections is. A conformal projection maintains all angles at each point, including those between the intersections of arcs. The purpose of this publication is to assist countries by providing a reference document that focuses on digital mapping aspect when conducting population and housing censuses. Pdf a guide to selecting map projections for world and. Maps and map reading are essential skills that all of the armed forces need. Pdf world map from a different perspective, placing the american continent in the center. 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. Scanned map datasets dont contain spatial reference information.
A geospatial pdf contains information that is required to georeference location data. Geotiff is a public domain metadata standard which allows georeferencing information to be embedded within a tiff file. For example, in the sinusoidal projection, the equator and all parallels are their true lengths. Traditionally, the role of maps in the census has been to support enumeration and to present aggregate census results in cartographic form. Map charts have gotten even easier with geography data types. When the central axis of the developable surface is oriented eastwest, the projections aspect is. When geospatial data is imported into a pdf, acrobat retains the geospatial coordinates. The potential additional information includes map projection, coordinate systems, ellipsoids, datums, and everything else necessary to establish the exact spatial reference for the file.
Because the projective transformation has the property that it projects points behind the center of projection to points in front of it, it is important to discard points with a negative z value. Lines along which scale distance is correct are the same proportional length as the lines they reference on the globe. Pdf is often associated with paperless office and used for printing and designing. If the cone touches the earth at just one particular parallel of latitude, it is called tangent. In cartography, a map projection is a way to flatten a globes surface into a plane in order to. For example, the basic mercator projection is unique. A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive.
A map is a drawing of a particular area such as a city, a country, or a continent. Although they can represent size, shape, distance and directions of the earth features with reasonable accuracy, globes are not. Dec 30, 2015 the shapefile format is now a common format for storing vector gis data shapefiles store nontopological vector data along with related attribute data. This article introduces projection wizard, an online map projection selection tool available at that. Use this procedure to convert a file from its current map projection to a specified output projection. But distortion in some form or the other is inevitable. The european petroleum survey group epsg code contains the reference system wgs84 and projection utm zone used to map the data. Handbook on geographic information systems and digital. It is also known as the babinet projection, homalographic projection, homolographic projection, and elliptical projection. The second chapter discusses, inter alia, costbenefit analysis of an investment in digital cartography and gis, plans for census cartographic process, digital map database development, quality assurance, database maintenance, and use of gis during census enumeration. Heres the recipe for a projected coordinate system. The selection of map projections is difficult and confusing for many. Projection function an overview sciencedirect topics.
Excel will automatically convert your data to a geography data type, and. The work of a map is to illustrate specific and detailed features of a particular. For the normal aspect, the apex of the cone lies on the polar axis of the earth. 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. 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. The robinson projection is a map projection of a world map which shows the entire world at once. A map projection is a systematic representation of all or part of the surface of a round body, especially the earth, on a plane snyder, 1987, map projections a working manual, usgs professional paper 95. 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. Heres what a projection file looks like on the inside. It is possible to design a map such that some of the four remain undistorted by selecting an appropriate map projection. To make these representations, the cartographer must calculate geographic features so that they are represented as close to real as possible. Its simple, easy to read and was created by the open gis consortium.
Please also check our more detailed, editable america. Handbook on geographic information systems and digital mapping. 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. M 1900 2200 oblique mercator 2301 2302 2401 2402 2509 and 2506 or or 2507 2508. 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 done by projecting the geo points onto the flat surface and creating distortions of the original points. A map projection is a geometric function that transforms the earths curved, ellipsoidal surface onto a flat, 2dimensional plane. Lecture 2 map projections and gis coordinate systems. Area of use values are in decimal degrees based upon wgs 1984. Charts designed to meet requirements of aerial navigating, produced in several series, each on a specified map projection and differing in scale, format, and content, for use as dictated by type of aircraft and whether flight is to be conducted under visual or instrument flight rules. Please also check our more detailed, fully editable world map.
Georeferencing arcmap defini ng a projection a georeferencing a raster dataset raster data is obtained by scanning maps or collecting aerial photographs and satellite images. The choice of projection depends on the intended use of the map. Geo327g386g lab 2 map projections and coordinate systems. These methods enable map makers to control the distortion that. Industry employment and payroll information is produced both quarterly and annually for the state, labor market areas, workforce development areas, cities and towns, and counties. The shapefile format is now a common format for storing vector gis data. The projection parameters these depend on the locality a datum, which defines the datum shift algorithm, the datum shift parameters, and the ellipsoid definition. Every distinct map projection distorts in a distinct way, by definition. Simply input a list of geographic values, such as country, state, county, city, postal code, and so on, then select your list and go to the data tab data types geography. Cartography definition, types and elements the international cartographic association defines cartography as the discipline dealing with the conception, production, dissemination and study of maps. This handbook is intended to be a coordinate reference systems user manual, therefore we assume some knowledge and prior exposure to basic concepts of map projections and coordinate reference systems.
It was specifically created in an attempt to find a good compromise to the problem of readily showing the whole globe as a flat image. This template help you guide the planning phase and help to share key milestones with your team members and stakeholders. Small fonts are fine, but dont go below 6 thats too small. With the coordinates, you can view and interact with the pdf to find and mark location data. Cities and towns in an area employment and wage es202 data are derived from reports filed by all employers subject to unemployment compensation laws, both state and federal. Maps are a twodimensional representation of a threedimensional world. For example, shapefiles can be directly read by a number of gis software programs such as arcgis.
A projection that maintains scale along one or more lines, or from one or two points to all other points on the map. Map projection projections transform the curved, threedimensional surface of the earth into a flat, twodimensional plane. This topic shows how to use the map function to view projections, and how to warp a map image to a map projection. Slideshare uses cookies to improve functionality and performance, and to. Exercise 1 defining projections when adding a reader in this scenario, you want to define the projection of your dataset to match the coordinate system information that is stated in a metadata file. For example, the sinusoidal is called a pseudocylindrical projection because all lines of latitude are straight and parallel and all meridians are equally spaced. 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. In fact, it is a single string written in wellknown text format, or wkt. This requires the definition of the geodetic datum, the reference ellipsoid and the map projection. All map projections have distortions distance, area, direction, andor shape. Map projection transformation is an area of research in mathematical cartography newly developed over the last 25 years. Map definition and meaning collins english dictionary. A map projections aspect is its orientation on the page or display screen.
For example, the line of latitude or longitude where a projection intersects or cuts the earths surface is called the point of contact, or standard line, where distortion is minimized. Developers set the goal to create a format that can be displayed and opened the same on any device. Map makers attempt to transfer the eartha round, spherical globeto flat paper. Indeed it would be beyond the abilities of todays geospatial professionals to produce a map projection without a computer. Townships are further subdivided into 36 numbered sections of 1 square mile 640 acres each. This projection file has the same base name as the. The first fundamental form and the gaussian fundamental quantities are defined and applied to obtain the plotting equations and distortions in. This means that cartography is the whole process of mapping. The standard format for subdivision is by townshipsmeasuring 6 miles 480 chains on a side.
This procedure requires an input file, the output projection, and the resampling and warping method. The dialog box allows map projection definition and property modification. Map projections are the different techniques used by cartographers for presenting a round globe on a flat surface. The importance of map projections by sarah lyle on prezi. Direction and shape are good at the equator to about latitude 40 44 n and s. Understanding map projections landing page for kartoweb. Angles, areas, directions, shapes, and distances can become distorted when transformed from a curved surface to a plane. 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. In order to display some part or all of the earth on a flat surface, a map projection is required. Projection definition and coordinate transformation fme.
The topic map projection is very complex and even professionals who have studied geography, geodetics or any other gis related science, often have problems with the correct definition of map projections and coordinate reference systems. Because earth has a curving, notquite sphericial shape, planar maps of. Map projection definition of map projection by the free. If made smaller, the cone will intersect the earth twice, in which case it is called secant. And embedded in the software will be mathematical algorithms. Planar, azimuthal or zenithal projection conic projection cylindrical projection mathematical or conventional projection. A conic projection is derived from the projection of the globe onto a cone placed over it. This book reflects several aspects of the development of modern mathematical cartography, especially the theory and methods of map projection transformation. Requirements for projection definition include the following header rec ords. Because earth has a curving, notquite sphericial shape, planar maps. Usually when you work with gis, you already have projected data to start with.
The problem with projections is that they change the surface in some way. May 14, 2015 the projection file is really just a simple text file with keywords in a specific format. Geospatial data can be either vector or raster based or a combination of both. Shapefiles store nontopological vector data along with related attribute data. If north or south is straight up, the aspect is said to be equatorial.
Idls map function allows you to view more than 30 different map projections. In other equidistant projections, the equator and all meridians are true. In a conformal projection, graticule lines intersect at 90degree angles, and at any point on the map the scale is the same in all directions. Advantages and disadvantages of pdf format logaster. Another example is the robinson projection, which is often used for smallscale thematic maps of the world it was used as the primary world map projection by the national geographic society from 19881997, then replaced with another compromise projection, the winkel tripel. Map projection definition, a projecting or protruding part. Pdf projection wizard an online map projection selection tool. 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. We will now examine map projections used for the continental united states. The study of map projections is the characterization of these distortions. This procedure converts among many projections in envi classic.
The purpose of the map determines which projection should form the base for. Map makers have devised methods for taking points on the curved surface of the earth and projecting them onto a flat surface. Mathematics and computers are the indispensable allies of map projection. 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. A map is a visual representation of an entire area or a part of an area, typically represented on a flat surface. Project point onto projection plane and compute light 728. Whenever you select a new crs, the layer units will automatically be changed in the general tab of the project properties dialog under the project or settings. In order to display some part or all of the earth on a flat surface, a map. There are thousands of different map projections all depending on how they intersect earths surface and how they are oriented. The map grid and bin grid reference frames the map grid coordinates are referenced to a geodetic coordinate framework. A map projection is a way of showing the surface of a threedimensional sphere on a flat surface. Feb 21, 2011 we use your linkedin profile and activity data to personalize ads and to show you more relevant ads.
Developed by esri, shapefiles are now an open format and is a popular option for data transfer. Map projectionspdf versions of numerous projections. The mollweide projection is an equalarea, pseudocylindrical map projection generally used for global maps of the world or night sky. Map projections map projections are mathematical formulas used to transfer shapes from an oval surface the earth surface more accurately, a model of it onto a flat surface.
The references and resources section in this handbook provides additional references. Define map axes and modify map projection and display. In this lab, we will assess map projection differences for the conterminous us. Working with projections qgis documentation documentation. It is also modeled more accurately as an oblate spheroid or an ellipsoid. We will create a map layout with multiple data frames in it four maps in one page, and we will create a new shapefile in different map projections. The ellipsoid is the regular shape chosen to approximate the irregular earth, defining an angular. This projection file has the same base name as the shapefile and a. It is impossible to map a curved earth on a flat map using plane coordinates without distorting angles, azimuths, distances, or area. The map projection applied to the processed archive data level1c. For instance, for the shapefile format this is a file containing the wellknown text wkt representation of the layers crs. If the screen will only be used with one type of projector ntsc video, hdtv, etc. Lambert conformal format noaa earth system research laboratory.
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