A gcs is often incorrectly called a datum, but a datum is only one part of a gcs. 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. It also defines its map extent, or the maximum coverage over the earth of a box. The definition of the map projection for projected coordinate systems. In the event that you cannot, you can create a custom coordinate system to display the data. Georeferencing, map projections, cartographic concepts. Purchase coordinate systems and map projections 2nd edition. Rectangular coordinate system uses x,y coordinates to represent positions on a plane. The figure of the earth and the reference surfaces used in surveying and mapping. Projected coordinate systems, map projections, parameters, and linear units of measure.
Georeferencing, map projections, cartographic conceptsmap projectionscoordinate systemsdatum. A projected coordinate system such as universal transverse mercator utm, 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 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. The term coordinate system, which includes both geographic and projected coordinate systems, is used to describe the information about the projection, as well as other specifics, such as datum, units, and meridians. Spcs was established to support surveying, engineering, and mapping activities in the united states and its territories. A tutorial on map projections and geographic coordinate systems. Understanding map projections landing page for kartoweb. Objectives coordinate systems and map projections for gis. Mar 10, 2015 spatial referencing system map projection and coordinate system with arcgis 10. The course format includes detailed information on how these concepts are applied to.
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 accurate depiction of a 3dimensional body on a 2dimensional surface is impossible. Choosing an appropriate coordinate system for your map is often an important step to create a map display that will meet your needs. Circumference of lines of latitude getting smaller, maps width staying constant. Nov 14, 2019 to select a map projection, determine which of the properties is the most important for the project, and select the coordinate system or map projection that best preserves that property. This means different y scales in different parts of the map what is the xscale factor. The modern topographic map was also created to the scale 1. There are over 4000 coordinate systems in the arcgis platform, so it is likely that you can find one to match your data. Geodesy, map projections and coordinate systems synopsis of class 6, gis in water resources, fall 2011. Defines origin and orientation of the coordinate axes as well the sizeshape of earth a map a 2d representation of the 3d earth with eastingnorthing coordinates an overview of ellipses, datums, and projections the projection.
You can choose coordinate reference system parameters in tntmips when you establish georeference control for your project materials, when you import georeferenced data, or when. The relationship between a distance portrayed on a map and the same distance on the earth all three properties can be controlled through the scale factor scale factor grid projection length datum length scale factor is a ratio of a length on projection surface to the. Coordinate systems, map projections, and geographic datum. Mathematical calculations are used to convert the coordinate system used on the curved surface of earth to one for a flat surface. Map projection, data frame and coordinates system geonet. The map of massachusetts in unprojected decimal degrees of longitude and latitude note the proportion of the lines and the circle.
Map projection is a method of producing a flat map representation of a portion of the earths surface. In any case, it is extremely important, as a user, to know the projection and coordinate system of all the data you use. Just as all maps have a map scale, all maps have locations, too. Project the globe onto a 2d surface there are lots of. As described under map projections, traditional coordinate systems are based on a flat coordinate system. To select a map projection, determine which of the properties is the most important for the project, and select the coordinate system or map projection that best preserves that property. Coordinate systems and map projections, second edition. Introduction to maps,coordinate system and projection system. Since such a map will cover a large area we want a projected coordinate system that will show the entire world in an attractive way, but also minimizes distortion from the projection process.
Map projections are introduced on pages 1012, and pages. The signs of x and ycoordinates in a projected coordinate system. Page 79 discuss map scale and the basics of coordinate systems. Understanding projections and coordinate systems important knowledge to have, especially if you deal with many different sets of.
Dec 03, 2011 map projection is a set of techniques designed to depict with reasonable accuracy the spherical earth in a twodimensional i. Coordinate systems frameworks used to determine position on the surface of the earth. Dec 09, 2014 rectangular coordinate system uses x,y coordinates to represent positions on a plane. Map projection involves transforming spatial data defined on the curved surface of the earth to the flat surface of a map. Some basic ideas about the mathematics of map projections.
A map projection is a rigorous mathematical means of translating a particular region of our earths curvaceous threedimensional surface into a flat twodimensional representation. Answering these questions will determine what map projection and projected coordinate system youll want to use to display your data. Map projections can be generally classified according to what spatial attribute they preserve. In the translation from a spherical surface to a twodimensional, flat surface, a change in the expression of points occurs. 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 two. Projections transformation of curved earth to a flat 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. So most of the time, the maps coordinate system is the same as the coordinate system of your geographic data. Updating the coordinate system properties of a dataset. Map projection earth surface in reality is a curved surface with no perfect geometrical shape. The location of any point in this system is defined by a set of two values, p x, y. 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. However, many maps must use a specialized map projection in order to meet a particular requirement.
Mathematical cartography also takes in map scales and their variation, the. A map projection is a systematic transformation of the latitudes and longitudes of positions on the surface of the earth to a. A coordinate system provides a framework for referencing locations on a map to locations in the real world. The default coordinate system used by arcgis explorer online is called web mercator auxiliary sphere. This selfpaced, online training teaches the fundamental concepts of map projections, datums, and coordinate systems and demonstrates how to use them using esris arcgis. A projection is a mathematical formula for translating information from the curved surface of the earth to a flat, planar map. Coordinate systems for map displayhelp arcgis for desktop. Coordinate systems and map projections 2nd edition. The process of projection involves distorition of area, distance, shape, and angles. The map above describes the position of the city of melbourne, florida using the transverse mercator projection. A map projection is the mathematical algorithm used for this transformation. Arctoolbox allows the transformation of data from one map projection to another. Under related information below, click the link titled projections table 2009 to access.
The shape of the earth and the geodetic datum concept are covered on pages 46. Thus, any map projection causes distortion in the shape, area, distance, scale or direction of the data. The extent, location, and property you want to preserve must inform your choice of map projection. Map projections and coordinate systems gis courses. 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. 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.
Map projection types are created by an imaginary source of light projected inside the earth. 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. The process of converting a threedimensional space to a twodimensional map is called projection. What is a coordinate system a coordinate system defines the location of a point on a planar or spherical surface a geographic coordinate system is a threedimensional reference system that locates points on the earths surface. A map projection uses mathematical formulas to relate the spherical or ellipsoidal coordinates on the globe to flat, planar coordinates. 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. Geodesy, map projections and coordinate systems gis in water resources, fall 2015.
The earth exists in threedimensions but, other than globes, most representations of the earth are two dimensional. The central focus of this book is on the theory of map projections. Any planar coordinate system is based on a map projection, which is the orderly transfer of positions or places on the surface of the earth to c orresponding points on a twodimensional surface, like a sheet of paper. If a dataset has no projection defined, it is possible to use the software to define the projection, that is, to add extra data that describe the projection and coordinate system of the dataset. There are several ways to refer to a coordinate system.
Map projection can be best visualized by imagining a light bulb placed at the center of a transparent globe and having its lines of longitude and latitude cast upon either a flat sheet of paper or a sheet of paper rolled into a cylinder or cone placed over the globe. A coordinate system, datum, and map projection are all components of the coordinate reference system for a spatial object. Spatial referencing system map projection and coordinate system with arcgis 10. A projected coordinate system based on a map projection such as transverse mercator. Small scale global, continental maps a small scale map covers a large area. Some people casually refer to any coordinate system as a projection, but this is not strictly true. Coordinate systems and map projections 2nd edition elsevier. 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. This example shows the formulas defining the mercator projection for a sphere. For instance, in geometry we use x horizontal and y vertical coordinates to define points on a twodimensional plane.
A handy map of universal transverse mercator system zones by alan morton. Geodesy, coordinate systems, objectives and map projections. Coordinate systems, projections, and transformations. Geodesy, projections, and coordinate systems 117 surface. Given a cylindrical projection, the x scale must increase away from equator. Select a suitable map projection or coordinate system. The signs of x,y coordinates in a projected coordinate system. 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. The bounding coordinates of the map are 20n, 90w for the southwest corner to 40n, 70w in the northeast corner. Georeferencing, map projections, cartographic concepts map. Map projection is the process of systematically transforming positions on the earths spherical surface to a flat map while maintaining spatial relationships. They are almost always a positive quadrant coordinate system, and are easier to develop and use over a small area. Geodesy, map projections and coordinate systems synopsis.
Geodesy, map projections and coordinate systems gis in. Arctoolbox permits the transformation of data from one map projection to another. A map projection transforms latitude and longitude to x and y coordinates in a projected coordinate system. 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. Mapping in a globe is an easy way to map the earth. Map projection, coordinate system and datum content writer. The appearance, classification and naming of map projections.
In romania, over time many cartographic projections were. Units of measurement typically feet or meters for projected coordinate systems or decimal degrees for latitudelongitude. Coordinate systems enable geographic datasets to use common locations for integration. Spatial referencing system map projection and coordinate. 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. We use your linkedin profile and activity data to personalize ads and to show you more relevant ads. A gcs includes an angular unit of measure, a prime meridian, and a datum based on a. Within the 2dimensional universal transverse mercator utm coordinate system positions are expressed as the number of metres east of the central meridian. So most of the time, the map s coordinate system is the same as the coordinate system of your geographic data. Geographic coordinates, latitude and longitude, are in fact not considered projected. Lecture 2 map projections and gis coordinate systems.
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. Map projection, coordinate system and datum youtube. Understanding map projections, datums, and coordinate systems. This is defined uniquely for a feature dataset within a geodatabase, and serves to. Apr 26, 2011 we use your linkedin profile and activity data to personalize ads and to show you more relevant ads. Map projection and coordinates chiang mai university.