Selecting map projections in minimizing area distortions in gis applications article pdf available in sensors 812 december 2008 with 327 reads how we measure reads. We will taker a closer look at the popular mercator projection and examine how the projection. Create a custom projection file in arcmap to align cad data summary. A gis without coordinates would simply be a database like microsoft excel or access. However, if you want to make sure that all of the data you are using in a project has the same coordinate system for consistency and accuracy in analysis and editing, or to minimize. Gis data is created in one of two types of coordinate systems. Checking this setting will disable all projection handling within the qgis project, causing all layer and map coordinates to be treated as simple 2d cartesian coordinates, with no relation to positions on the earths surface. Map projections there are many different map projections.
The geoid is defined as the surface of the earths gravity field, which is approximately the same as mean sea level. In the process of projection the earth is represented by a model an ellipsoid. This process is typically, but not necessarily, a mathematical procedure some methods are graphically based. Every dataset in arcgis has a coordinate system which defines its map projection. A map projection is the mathematical algorithm used for this transformation. Introduction to map design introduction this document is intended to help people without formal training in map design learn to produce maps for publication or electronic display using arcview, a desktop geographic information system gis. A map is a representation of the spatial organization of the physical universe at any scale. Coordinate systems, projections, and transformations arcgis pro. The crs tab also has an optional setting for no projection. Low distortion map projections for engineering, surveying, and gis conference paper pdf available july 2016 with 399 reads how we measure reads. In cartography, a map projection is a way to flatten a globes surface into a plane in order to make a map. One easy way to identify whether a dataset uses a geographic or projected.
The following concepts are fundamental to understanding the use of map projections in arcgis. Map projection is a very complex topic and we cannot cover it completely here. Area of use values are in decimal degrees based upon. Esri, arcgis, the arcgis logo, arcinfo, arcglobe, and are trademarks, registered. It is thanks to the coordinates that we can create overlays in a gis and perform analyses that incorporate data from more than one. Npmap symbol library the npmap symbol library is the national park services web map icon set. Since the mass of the earth is not uniform at all points, and the direction of gravity changes, the. The interactive webmaps provide you with access to lethbridges most current geographic data in a map you can search, customize, or print. Equal earth map projection meets cartographic needs and.
It is important for a gis analyst to have a thorough understanding of map projections and coordinate systems. As implemented in geographic information systems, projections are transformations from spherical coordinates to xy coordinates systems and transformations from one xy coordinate system to another. Types of map projections the number of map projections made possible is limitless, and hundreds have been published. 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. Working with map projections and coordinate systems in arcgis mahmoud abdelrahman. A map projection is one of many methods used to represent the 3dimensional surface of the earth or other round body on a 2dimensional plane in cartography mapmaking. Working with map projections and coordinate systems in arcgis. Instructions provided describe how to create a custom projection file for cad data, and how to align the cad file with other data in a projected coordinate system with units of feet, meters or other linear units. Map projections explained a beginners guide youtube.
All projections of a sphere on a plane necessarily distort the surface in some way and to some extent. How to define map projections making sure your gis data is in the right place on the map as people share their data over the web, its becoming more important to define the coordinate system to ensure that a dataset displays in its proper location and aligns correctly with other data. Welcome to the wonderful world of geographical information systems gis. A paper describing the equal earth projection, written by patterson, jenny, and savric. Although the earth is best represented by a spheroid, the earth is sometimes treated as a sphere to make mathematical calculations easier. Coordinate systems, also known as map projections, are arbitrary designations for spatial data. Arcgis pro and arcmap will projectonthefly to make your data draw with whatever coordinate system your map is using, and it will draw in the right place. A gis is a system for the display, analysis, storage and retrieval of information about places on the earth. Iliffe, jonathan and lott, roger, datums and map projections.
Arctoolbox permits the transformation of data from one map projection to another. Because there is no limit to the number of possible map projections, there can be no comprehensive list. The map scale may be expressed in three ways and the pictorial representation of these three types is shown in the figure. All map projections distort at least some of the following. It is perpendicular to the direction of gravity pull. Area of use values are in degrees based upon wgs 1984. Coordinate systems, projections, and transformations arcgis. Doc page 4 of 14 the yale map collection at sterling memorial library wall street, room 707 stacey maples gis assistant 2034328269 stacey. This requires a systematic transformation of the latitudes and longitudes of locations from the surface of the globe into locations on a plane. The location shape size of the region to be mapped the theme or purpose of the map 37 38. The spatial or map extent covered by the dataset often referred to as the spatial domain learning more about coordinate systems.
Choosing a map projection the choice of map projection is made to give the most accurate possible representation of the geographic information, given that some distortion is inevitable. In the event that you cannot, you can create a custom coordinate system to display the data. Working with projections qgis documentation documentation. Learn what a map projection is, why they are used and what impact they have on maps gis systems. Gis gps education last updated 052901 what is a map projection. Individual shapefiles have a projection, and the data frame has a projection. Please note though that the topic of projections is extremely broad, and this article can do no more than touch on a few important topics.
Learning more about map projection and coordinate system concepts. Additional information on these topics is also available from numerous online gis knowledgesharing communities. Area of use values are in decimal degrees based upon wgs 1984. Handbook on geographic information systems and digital. Both of these need to be defined for your data to display properly. Brief overview of map projection using arcgis map projection involves taking spatial data defined on the curved surface of the earth and transforming it to the flat surface of a map.
The extent, location, and property you want to preserve must inform your choice of map projection. Each of the pictographic symbols has been carefully adapted to address legibility and accessibility needs specific to the web. A map projection is a rigorous mathematical means of translating a particular region of our earths curvaceous. It allows the reader to see quickly, if one map can be compared with another. Create a custom projection file in arcmap to align. This is a summary of map projections that have articles of their own on wikipedia or that are otherwise notable. In this series, we talk about the basics of map projections, including coordinate systems and datums. Map projections distortions projection refers to the notion of shining light through the earth surface and projecting latitudes, longitudes and geographic features onto a developable surface. Lethbridge streets, parks, ice centres, sports fields, pools, golf courses, trails, recycling depots, census demographics and aerial photography. 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. In this module, we introduce the qgis itself, as well as explaining the user interface, how to import data, and create simple maps. Map projections displaying the earth on 2 dimensional maps the world from space projection from esri, centered at 72 west and 23 south. Arcgis 10 arcmap projection and coordinate systems. Map projection a map projection is a systematic transformation of the latitudes and longitudes of locations on the surface of a sphere or an ellipsoid into locations on a plane.
Projections are chosen based on the needs of the map or data analysis and on the area of the world. Projection is how the 3d earth is mapped on a 2d planar surface paper map or digital gis. Without a coordinate system a map is just a drawing. Common coordinate system and map projection tasks in arcgis.
This approximates the view of the earth from the sun on the winter solstice at noon in cambridge, ma. Lecture 2 map projections and gis coordinate systems. Although the earth is best represented by a spheroid, the earth is sometimes treated as a sphere. Unit of measurement typically feet or meters for projected coordinate systems or decimal degrees for. Spatial data has coordinate systems, geographic coordinate systems, or projected coordinate systems defined. After completing this section, you will be able to correctly identify the main elements of the screen in qgis and. The equal earth map projection became one of the journals most read papers, with more than 12,000 views. There are over 4000 coordinate systems in the arcgis platform, so it is likely that you can find one to match your data. How do i define or change map projection in arcgis. Quick start guide to map projections national geospatial.
314 813 1290 1547 158 1082 656 354 1161 1374 1543 1629 369 877 855 751 712 893 1601 372 863 985 872 1418 647 66 1253 1314 94 833 224 560 719 27 603 773 1397 454 1214