Map projection enables a map user to work with twodimensional coordinates, rather than spherical or threedimensional coordinates. Since planet earth isnt flat,some distortions in the data will inevitably occurduring that transformation process. Because degrees of latitude and longitude dont have a standard length, you cant measure distances or areas accurately or display the data easily on a flat map or computer screen. This includes cad data and data and shape files created with arcmap before 2002. Coordinate systems, projections, and transformationsproperties of. 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 a map projection transforms latitude and longitude locations to x,y coordinates. Certification of completion esr certifies that has successfully completed the esr e sri training and education mtraining. Understanding difference between coordinate system and. Making sure your gis data is in the right place on the map. The definition of the map projection for projected coordinate systems. Understanding coordinate systems and projections for. Projected coordinate systems a map projection is the systematic transformation of locations on the earth latitudelongitude to planar coordinates the basis for this transformation is the geographic coordinate system which references a datum map projections are designed for specific purposes.
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. Oct 08, 20 presentation objectives understand basic concepts on coordinate systems for the gis user. Geographic coordinate systems are based on a spheroid and utilize angular units degrees. This book explains in a clear and complete manner the terms and concepts of map projections and how they can be applied to your data.
Certification of completion esr certifies that has successfully completed the. Map projections and coordinate systems in gis map projection transforms the spatial relationship of map features on the earths surface to a flat map. Any data projected as projected coordinate system pcs has in addition its underlying geographic coordinate. Geodesy, coordinate systems, objectives and map projections. Data that uses a projected coordinate system usually has an extent with six to eight digits to the left of the. Datums, coordinate systems, coordinate reference systems and. 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. The shape of the earth and the geodetic datum concept are covered on pages 46. This enables you to create a map that accurately shows distances, areas, or directions. Map projection, coordinate system and datum duration. Whether familiar with the science and mathematics involved with projecting geographical data or learning it for the first time, this book will help users understand the difference between geographic and projected coordinate systems. Gis needs to be able to register data from different. Thematic mapping using countries and us states as an example, map projections, coordinate systems, data classi.
Gis positional data are primarily printed maps which have been digitized. Lecture 2 introduction to gis based on lecture notes of. A geographic coordinate system gcs uses a threedimensional spherical surface to define locations on the earth. 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. More information about coordinate systems is available through arcgis 10. Map coordinate systems winforms controls devexpress. This is the longitude grid for southern california.
A gcs includes an angular unit of measure, a prime meridian, and a datum based on a spheroid a point is referenced by its longitude and latitude values. The difference is that wgs 84 is a geographic coordinate system, and utm is a projected coordinate system. If layers in a map have different coordinate systems defined from those of the map or local scene itself, a transformation between the. Objectives coordinate systems and map projections for gis. Datums, coordinate systems, coordinate reference systems. Coordinate systems either geographic or projected provide a framework for defining realworld locations. 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. 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. Coordinate reference system selector this dialog helps you assign a coordinate reference system to a project or a layer, provided a set of projection databases. Going further with gis exploring and evaluating online sources for free data, exploring open source. Understanding coordinate systems, datums and transformations in australia. Terminology what all those words really mean geodesy the shape of the earth geographic coordinate systems datums map projections projected coordinate systems working with projections in arcgis understanding coordinate systems for arcgis 3. Map projections are used to represent a spatial 3dimensional surface e. The map of massachusetts in unprojected decimal degrees of longitude and latitude note the proportion of the lines and the circle.
Pdf on jan 1, 1994, melita kennedy and others published understanding map. Understanding map projections introduces and illustrates what geographic and projected coordinate systems are and the elements that make up each. All of them transform a location coordinate on the globe, a spherical longitudinal latitude and unitless point in a surface that needs x and y with in a longitudinal unit. A projected or planimetric coordinate system that maps locations on the earths three dimensional surface. These show up as distortions of area,shape, direction, distance, and scale. Understanding map projections and coordinate systems 18 course hours january 7, 2011.
Various map projections try and minimize the distortions, but no projection can eliminate all distortions all at once. Coordinate systems are referenced to the physical earth surface through the use of datums. Understanding map projections melita kennedy, steve kopp. Coordinate systems frameworks used to determine position on the surface of the earth.
A gcs is often incorrectly called a datum, but a datum is only one part of a gcs. Project the globe onto a 2d surface there are lots of ways to do each step, resulting in lots of coordinate reference systems. John schaeffer, juniper gis this presentation will take the mystery out of projections, coordinate systems, and datums. These show up as distortions of area, shape, direction, distance, and scale. The remaining half of the book presents attributes of over sixty supported map projections in arcgis. This book introduces and illustrates geographic and projected coordinate systems and offers information on how they can be applied to data. To adjust errors which occur at map digitization due to distortion of the map measured, 6. If you know the epsg code, the identifier, or the name for a coordinate reference system, you can use the search feature to find it. Projected coordinate systems, map projections, parameters, and linear units of measure current as of arcgis version 9. Understanding projection and coordinate systems linkedin. Understanding projections and coordinate systems important knowledge to have, especially if you deal with many different sets of. Intro to coordinate systems and utm projection youtube.
For a conceptual overview, see georeferencing and coordinate systems. To define the coordinate system for external raster and image files. The employed plane coordinate system is either projected or geographic. So we should get used to understanding map projections and their properties.
Lecture 2 map projections and gis coordinate systems. Projected coordinate systems are sometimes referred to as map projections. A coordinate reference system crs then defines, with the help of coordinates, how the twodimensional, projected map in your gis is related to real places on the earth. Whenever you make a map,youre abstracting information about the real world,and placing it onto a flat plane,such as a computer screen or a piece of paper. If layers in a map have different coordinate systems defined from those of the map or local scene itself, a transformation between the coordinate systems might be necessary to. The drawing at the bottom of figure 339 shows lines estimating approximately equal scale distor tion for a transverse mercator projection centered on the usa. To produce geocoded image by integrating gis data and remote. Map projections and coordinate systems gis courses. Projected coordinate systems are based on a plane the spheroid projected onto a 2d surface and utilize linear units feet, meters, etc. Coordinate systems, map projections, and geographic datum. Whenever you make a map, youre abstractinginformation about the real world and placing iton to a flat plane such as a computer screen or a piece of paper. Coordinate systems and map projections 2nd edition. From the perspective of a geographic software design three coordinate systems can potentially be addressed.
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. Understanding projections and coordinate systems important knowledge to have, especially if you deal with many different sets of data that come from different sources. Whether familiar with the science and mathematics involved with projecting geographical data or learning it for. 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. Spatial data can also be expressed using projected coordinate systems pcs. Understanding coordinate systems and map projections. This is changing somewhat as more data are collected by gps. 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. Project converter assembly deployment tool localization service quality assurance and productivity. The basic concepts behind map projections explained. Understanding coordinate systems and projections for arcgis. Just as all maps have a map scale, all maps have locations, too.
Each differ either in the order of the coordinate tuple or in the direction of increasing values. To transform different map projections of many gis data sources to an unified map projection in a gis database, 5. Spatial data has coordinate systems, geographic coordinate systems, or projected coordinate systems defined. Page 79 discuss map scale and the basics of coordinate systems. Projections are a mathematical transformation that take spherical coordinates latitude and longitude and transform them to an xy planar coordinate system. Given that geographic datasets are primarly concerned with spatial references, we really must have metadata data about the data describing the coordinate system that is embedded in the files. Identifying the coordinate system typegeographic or projected. Use arcgis for mapping and visualization open an arcgis pro project change symbology. Since the planet earth isnt flat, some distortions ofthe data will inevitably occur during the transformation process. Understanding map projections landing page for kartoweb.
If layers in a map have different coordinate systems defined from those of the map or local scene itself, a transformation between the coordinate systems might be necessary to ensure data lines up correctly. The decision as to which map projection and coordinate reference system to use. Apr 08, 2016 intro to coordinate systems and utm projection. Map projections and coordinate systems before beginning this exercise, read about coordinate systems and map projections at. 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, projections, and transformations.
A tutorial on map projections and geographic coordinate systems. There are countless map projections, each one trying to achieve a minimal distortion on a feature important for the purpose of the map. A gcs includes an angular unit of measure, a prime meridian, and a datum based on a. Projected coordinate systems are derived from map projections and geographic coordinate systems from latitude and longitude degrees.
Understanding map projections, datums, and coordinate systems. Map projections are introduced on pages 1012, and pages. This short book starts with an overview of geographic and projected coordinate systems then discusses geographic transformations. In the united states, the most commonly used projected coordinate systems are state plane and universal transverse mercator utm. Docs controls and libraries map control coordinate systems map coordinate systems. Projections transformation of curved earth to a flat map. Coordinate systems enable geographic datasets to use common locations for integration. There are plenty of datasets that do not include such machine readable metadata. For instance, in geometry we use x horizontal and y vertical coordinates to define points on a twodimensional plane. The course format includes detailed information on how these concepts are applied to different regions of the pacific islands.
Coordinate systems, on the other hand, are how we locate a point on the earth. Projected coordinate systems projected coordinate systems pcs commonly use units of feet or meters. Maling gis applications spring 2004 objectives malings assumption. To understand geographic coordinate systems and latitudelongitude.
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