Sep 20, 2019 this selfpaced, online training teaches the fundamental concepts of map projections, datums, and coordinate systems and demonstrates how to use them using esris arcgis. Coordinate systems enable geographic datasets to use common locations for integration. A projected coordinate system is a planar system that uses twodimensional coordinates and linear distance measurements as units. Then click next and follow the directions in the appropriate procedure below. When a map portrays areas over the entire map so that all mapped areas have the same proportional relationship to the areas on the earth that they represent, the map is an equalarea map area in projections, scale varies from place to place. Handbook for transformation of datums, projections, grids. Models of map projections there are two models for creating different map projections. There is no limit to the number of possible map projections. Equalarea and equidistant projections appear in the national atlas.
Gis data differs from other data types, primarily because it contains geographic coordinates describing the location of the data on the earth. Coordinate systems frameworks used to determine position on the surface of the earth. In the create coordinate system wizard, on the specify starting point page, specify whether to start with a coordinate system, or to first define or edit an ellipsoid or a datum. A map projection uses mathematical formulas to relate the spherical or ellipsoidal coordinates on the globe to flat, planar coordinates. Sep 15, 2017 working with map projections and coordinate systems in arcgis duration. Intro to coordinate systems and utm projection duration. Some projections treat the earth only as a sphere, others as either ellipsoid or sphere. The circle gives the impression that worcester is approximately the same distance from boston as new hampshire, and that the state is nearly five times longer, east to west, as it is northtosouth. The original data has no coordinate system definition the data was collected using a. The relationship between a distance portrayed on a map and the same distance on the earth.
A datum is a mathematicallydefined reference surface used to represent the size and shape of the earth. Spheroid or ellipsoid based systems, local systems. Map projections explained a beginners guide youtube. What it wont do is the geographicdatum transformation part if there are no transformations already set. All projections of a sphere on a plane necessarily distort the surface in some way and to some extent. Exploring map projections created using d3, map projection transitions provides an excellent way to visualize a wide range of map projections. Page 79 discuss map scale and the basics of coordinate systems. Circumference of lines of latitude getting smaller, maps width staying constant. In the translation from a spherical surface to a twodimensional, flat surface, a change in the expression of points occurs. If youre already familiar with projections and how they work and often dont. History, policy, and future directions 1 executive summary the state plane coordinate system spcs is a system of conformal map projections created by the national geodetic survey ngs. For larger scale maps, including topographic quadrangles and the state base map series, conformal projections such as the transverse mercator and the lambert conformal conic are used.
You are making a smallscale map such as a national or world map. Coordinate systems, map projections, and geographic datum. Systems introduces the mechanics of selecting coordinate reference system components. A coordinate system is a reference system used to represent the locations of geographic features, imagery, and observations, such as global positioning system gps locations, within a. A projected coordinate system is based on a geographic coordinate system and a map projection. Click map setup tab coordinate system panel create coordinate system definition. 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. Overview of coordinate reference systems crs in r coordinate reference systems crs provide a standardized way of describing locations. Being geospatiallyfriendly involves the ability to accurately, precisely. Unlike a geographic coordinate system, a projected coordinate system has constant lengths, angles, and areas across the two dimensions. Introduction to coordinate systems and projections fondren. The spatial or map extent covered by the dataset often referred to as the spatial domain learning more about coordinate systems here is a series of links to help you learn more about applying map projections and coordinate systems in your work. Geodesy, map projections and coordinate systems synopsis of.
How is the 3d surface of the earth modeled onto a 2d surface. Only the tm and utm projections are considered in this paper. The central focus of this book is on the theory of map projections. With a smallscale map, your choice of map projection determines the overall appearance of the map. Working with map projections and coordinate systems in arcgis duration. Just as all maps have a map scale, all maps have locations, too. The map of massachusetts in unprojected decimal degrees of longitude and latitude note the proportion of the lines and the circle. Map projections massachusetts institute of technology. Maps, coordinate reference systems and visualising geographic. Transform coordinates for position on a map converting latitude longitude degrees coordinates on a map pick gps lat & long or coordinates in a projection system from maptiler team. Geographic coordinates, latitude and longitude, are in fact not considered projected. It is possible, and even common for datasets to be in the same projection, but be referenced to different datums, and therefore have different coordinate values.
Map projections and coordinates a map projection is any method of representing the surface of a sphere or other threedimensional body on a plane. European commission joint research centre 2001 eur 20120 en institute for environment and sustainability map projections for europe edited by. Map projection, data frame and coordinates system geonet. In the translation from a spherical surface to a twodimensional, flat surface, a. A crash course to coordinate systems, map projections and. Although there has been no dearth of valuable books describing a wide range of map projec tions, an album of map projections is the. Some people casually refer to any coordinate system as a projection, but this is not strictly true. Learn what a map projection is, why they are used and what impact they have on maps gis systems.
The process of projection involves distorition of area, distance, shape, and angles. A map projection is a rigorous mathematical means of translating a particular region of our earths curvaceous threedimensional surface into a flat twodimensional representation. The present booklet provides a conceptual introduction to map projections, coordinate systems, and geodetic datums. The book concludes with a chapter on the abuse and misrepresentation of map. A projected coordinate system is defined on a flat, twodimensional surface. The course format includes detailed information on how these concepts are applied to different regions of the pacific islands. From our map projections you are aware that you must always be aware of how arcmap is transforming the geometry of your data to display on your map.
Coordinate systems and map projections, second edition. A horizontal datum is defined by an ellipsoid, and its fixation with respect to the surface of the earth. Some basic ideas about the mathematics of map projections. A gcs is often incorrectly called a datum, but a datum is only one part of a gcs. The easiest way to try to transfer the information onto a flat surface is to convert the geographic coordinates into an x and y coordinate system, where x is longitude and y is latitude. Map makers attempt to transfer the eartha round, spherical globeto flat paper. Using timedifferences, loranc can identify positions with an accuracy of onequarter of a mile. The datum is a integral part of the projection, as projected coordinated systems are based on geographic coordinates, which are in turn referenced to a datum. Specify a coordinate systemproperties of maps arcgis pro. Geodesy, coordinate systems, objectives and map projections. Many different crs are used to describe geographic data.
After decades of using only one map projection, the polyconic, for its mapping program, the u. Coordinate systems and map projections 2nd edition. Projection a process that involves conversion of data from geographic coordinates, lat long to projected coordinates. Understanding map projections, datums, and coordinate systems. A tutorial on map projections and geographic coordinate systems. Local navigation coordinates systems, such as loranc, define locations by referencing measurements of electronic signals. Lecture 2 map projections and gis coordinate systems. Making sense of projections and datums in arcgis 1102107 making sense of projections and datums in arcgis course length. To define a global coordinate system autocad map 3d 2016.
Work undertaken in the usa and ussr on the creation of suitable map projections obtained through numerical analysis has been included. Download the list of supported geographic and vertical coordinate systems. For example, with some projections, lines of latitude and longitude will appear curved. Map projections are used to transfer or project geographical coordinates onto a flat surface. A geographic coordinate system is a coordinate system that enables every location on earth to be specified by a set of numbers, letters or symbols. July 24th 30th, 2010 projections and coordinate systems page 2 projections, spheroids, datums and coordinate systems we are trying to represent a 3we are trying to represent a 3dimensional, roundish, lumpy earth on a flat map we cant do this unless we project this roundish object onto a flat surface a round planet on a flat map. We will taker a closer look at the popular mercator projection and examine how the projection.
Analytical derivation of some map projections including examples of pseudocylindrical and polyconic projections is also covered. Objectives coordinate systems and map projections for gis. Learn about geographic coordinate systems and map projections and how to work with them in arcgis pro. For instance, in geometry we use x horizontal and y vertical coordinates to define points on a twodimensional plane. Nearly all maps are an attempt to represent our environment generally earth in a twodimensional format. Geodesy, coordinate systems, and map projections objectives introduce the main concepts of geodesy coordinate systems, datums, ellipsoids, and geoids describe map projections and coordinate systems we use in gis two key questions what is the shape of the. Arcmap overview this oneday course teaches students the essentials of map projections and coordinate systems, and what they need to know about projecting geographic data with arcgis. Geological survey usgs now uses several of the more common projections for its published maps. The appearance, classification and naming of map projections.
At the end of the work day, all sectorsindustries have their own different needs, necessitating different map projections. Coordinate systems, projections, and transformations. Most repositories of spatial data provide longitudelatitude coordinates, although singlecountry data sources often use a countryspeci. Oct 25, 2016 arcmap will reproject all layers that have coordinate systems that arent the same as the data frames. A projected coordinate system is always based on a geographic coordinate system that is based on a sphere or spheroid. Geodesy, coordinate systems, and map projections objectives introduce the main concepts of geodesy coordinate systems, datums, ellipsoids, and geoids describe map projections and coordinate systems we use in gis two key questions what is the shape of the earth, and where are things on the earth. Pdf coordinate systems and map projections rcz uz on. The figure of the earth and the reference surfaces used in surveying and mapping. Purchase coordinate systems and map projections 2nd edition. 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 process of converting a threedimensional space to a twodimensional map is called projection. In cartography, a map projection is a way to flatten a globes surface into a plane in order to make a map.
A coordinate system is a reference system used to represent the locations of geographic features, imagery, and observations, such as global positioning system gps locations, within a common geographic framework. Map scale is concerned with reducing geographical features of interest to manageable proportions, coordinate systems help us define the positions of features on the surface of the earth, and map projections are concerned with moving from the threedimensional world to the two dimensions of a flat map or display, all of which are discussed in. Heres the recipe for a projected coordinate system. Projections and coordinate systems are a complicated topic in gis, but they form the basis for how a gis can store, analyze, and display spatial data. A projection is the means by which you display the coordinate system and your data on a flat surface, such as a piece of paper or a digital screen. The earth exists in threedimensions but, other than globes, most representations of the earth are two dimensional. The shape of the earth and the geodetic datum concept are covered on pages 46. This requires a systematic transformation of the latitudes and longitudes of locations from the surface of the globe into locations on a plane. There are several ways to refer to a coordinate system.
The basic concepts behind map projections explained. Understanding projections and coordinate systems important knowledge to have, especially if you deal with many different sets of data that come from different sources. Geodesy, map projections and coordinate systems synopsis of class 6, gis in water resources, fall 2011 the fundamentals of the material to be covered in this class are sufficiently extensive that this synopsis extends to three pages, rather than the two pages used previously. An album of map projections should enable read ers to sharpen and in some cases to correct their knowledge of the distances, directions, and relative areas of the world.
There are many different coordinate systems, based on a variety of geodetic datums, projections, and units in use geographic coordinate systems no projection. Pdf 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. The coordinates are often chosen such that one of the numbers represents a vertical position and two or three of the numbers represent a horizontal position. Projections and coordinate system linkedin slideshare. The act of systematically transposing a 3d to a 2d object is called projection, and its a key concept of cartography, the art and science of making maps. If you let arcmap choose the method for transforming the geometry in your data, you will very likely be portraying the directions sizes, shapes, and relationships of the entities in your map in a. A projected coordinate system based on a map projection such as transverse mercator, albers equal area, or robinson, all of which along with numerous other map projection models provide various mechanisms to project maps of the earths spherical surface onto a twodimensional cartesian coordinate plane. A projected coordinate system based on a map projection such as transverse mercator, albers equal area, or robinson, all of which along with numerous other map projection models provide various mechanisms to project maps. This means different y scales in different parts of the map. Within arcgis, coordinate systems are classified either as geographic coordinate systems latitude and longitude or projected coordinate systems such as the utm or state plane. Geomashup codecamp 2011 university of helsinki department of computer science a crash course to coordinate systems, map projections and data formats.
Map projections displaying the earth on 2 dimensional maps the world from space. All map projections distort the surface in some fashion. A gcs includes an angular unit of measure, a prime meridian, and a datum based on a. Ellipsoidal coordinate systems reference a mathematically derived spheroidal or ellipsoidal volumetric surface. The map projection contains the mathematical calculations that convert the geodetic locations to the planar system. The crs that is chosen depends on when the data was collected, the geographic extent of the data, the purpose of the data, etc. 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. Coordinate systems and map projections sciencedirect. Projections by presentation of a metric property would include equidistant, conformal, gnomonic, equal area, and compromise projections. Making sense of projections and datums in arcgis 1103107 making sense of projections and datums in arcgis course length. Geographic coordinates systems, on the other hand, are expressed in values of longitude and latitude. Map projections are introduced on pages 1012, and pages.
Map projection, coordinate system and datum youtube. Map projection concerns the science of mathematical cartography, the techniques by which the earths dimensions, shape and features are translated in map form, be that twodimensional paper or two or three dimensional electronic representations. Learning more about map projection and coordinate system concepts. Spcs was established to support surveying, engineering, and mapping activities in the united states and its territories. Projections transformation of curved earth to a flat map. Given a cylindrical projection, the x scale must increase away from equator.
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