Our study uses the geographic coordinate system but there are other coordinate systems that divide the globe differently, like the universal transverse mercator or utm coordinate system, this system divides the earth into 60 zones vertically, and 20 sections horizontally. Projected coordinate systems are sometimes referred to as map projections. Download the list of supported geographic and vertical coordinate systems. Though it was suggested millennia ago that the earth rotates once a day, this fact was not widely accepted until the 17th century, and was not firmly established until the 19th century. Choose the projected coordinate system folder or the geographic coodinate system folder, depending upon the coordinate systems of your other files and how you want to match them. You can give any location on earth latitude and longitude coordinates. Introduction much of this basic map coordinates material in these notes may be wellknown to many students in this class. Gis coordinate systems handle significantly larger scales than cad coordinate systems and deal with issues such as the curvature of the earth and terrain, which are insignificant to cad coordinate systems. It is based on a sphere or spheroid geographic coordinate system, but it uses linear units of measure for coordinates, so that calculations of distance and area are. Unlike a geographic coordinate system, a projected coordinate system has.
View of the united states in the geographic coordinates click on the new map file button to create a new map file, and save it as usa. The basis for this transformation is the geographic coordinate system which references a datum map projections are designed for specific purposes. To define the coordinate system for external raster and image files. If you choose create coordinate system or create coordinate system definition on the map setup tab, you will see a wizard. Arcmap will reproject all layers that have coordinate systems that arent the same as the data frames.
Coordinate systems, map projections, and geographic datum. Geodesy, datums, map projections, and coordinate systems introduction geographic information systems are different from other information systems because they contain spatial data. Chapter 9 coordinate systems intro to gis and spatial analysis. Each point can be designated merely by its x, y coordinates. Projected coordinate systems which are based on cartesian coordinates. The employed plane coordinate system is either projected or geographic. Understanding difference between coordinate system and. Select a suitable map projection or coordinate system. Presentation objectives understand basic concepts on coordinate systems for the gis user. Geodesy, map projections and coordinate systems synopsis.
The appearance, classification and naming of map projections. Click the add data button, and add the data with the unknown coordinate system to arcmap. Army corps of engineers topographic engineering center 7701 telegraph road alexandria. A geographic coordinate system is a reference system for identifying locations. Datums, projections, grids and common coordinate systems january 1996 approved for public release. Rightclick the name of the layer, click properties, and select the source tab. Geodesists use coordinate reference systems such as wgs84, nad27 and nad83. Here are the coordinates in dms of a control point in redlands, california, on the north american datum of 1983 nad 1983 or nad83. The input for the shapefile is in latlong without regard to projection. Coordinate systems enable geographic datasets to use common locations for integration. Learn more about spheroids and spheres geographic coordinate system,the coordinate values of your data will change. This chapter introduces geodesy, the science of measuring the shape of the earth, and map projections, the transformation of coordinate locations from the earths curved surface onto flat maps.
This selfpaced, online training teaches the fundamental concepts of map projections, datums, and coordinate systems and demonstrates how to use them using esris arcgis. Anyway, projected coordinate system 2d is always based on some angular coordinate system 3d. Unlike data in a geographic coordinate system that has its origin 0,0 coordinates, where the prime meridian crosses the equator off the west coast of africa, a local coordinate system can have its origin 0,0 anywhere on the surface of the earth. For a conceptual overview, see georeferencing and coordinate systems. 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. Projections and coordinate systems revisited you must understand this to become proficient in gis different projections for different purposes sometimes you really have to.
A gcs is often incorrectly called a datum, but a datum is only one part of a gcs. Articulate the leader in rapid elearning and communications. A gcs includes an angular unit of measure, a prime meridian, and a datum based on a. Coordinate systems are referenced to the physical earth surface through the use of datums. Geodesy, coordinate systems, objectives and map projections. Some basic ideas about the mathematics of map projections. Since the time of the ancient greeks it has been known that the earth was a spherical object rather than a flat surface. Projections and map design the course will continue core concepts of gis that began in the first course, including projections, coordinate systems, cartography, and the difference between raster and vector data models. Datum and projections coordinate systems georeferencing.
Gis coordinate systems, on the other hand, describe locations on the surface of the earth. Projected coordinate systems also use a zvalue to measure elevation. Projected coordinate systems are based on a plane the spheroid projected onto a 2d surface and utilize linear units feet, meters, etc. Geographic coordinates tutorial with online converter tool. The field of study that measures the shape and size of the earth is geodesy. The figure of the earth and the reference surfaces used in surveying and mapping. 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. Since the introduction of the state planecoordinate systems on the lambert and transverse mercator projections in 1935, numerous questions have arisen among prospective users of these systems concerning their applicability in connection with geological survey maps on the polyconic projection. Defining coordinates for the earths surface is complicated by two main factors. Understanding coordinate systems and projections for arcgis. Add the states and latlong feature classes to the data frame. These spatial data include coordinates that define the location, shape, and extent of. Understanding coordinate systems and projections for arcgis 1.
A tutorial on map projections and geographic coordinate systems. Nearly all projections are applied via exact or iterated mathematical formulas that convert between geographic latitude and longitude and projected x an y. Cad data is frequently created in a local coordinate system. If you create a coordinate system by duplicating and then editing an existing system in the coordinate system library, you will see a dialog box with sets of options listed on the left. Data is defined in both horizontal and vertical coordinate systems. This pdf file lists map projections supported in arcgis desktop version 10. I am trying to display a shapefile over this landsat image, but the shapefile is in wgs84 which is a geographic coordinate system in arcmap. In the extent section, note the number of digits to the left of the decimal in top, bottom, left, and right positions. Lecture 2 map projections and gis coordinate systems.
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. Geographic coordinate systems are based on a spheroid and utilize angular units degrees. Introduction to maps,coordinate system and projection system. Once the value of k is defined,the value of m can be got,so they can be transformed according to the scale factor.
Horizontal coordinate systems can be of three types. Ellipsoidal coordinate systems reference a mathematically derived spheroidal or ellipsoidal volumetric surface. 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. Working with map projections and coordinate systems in arcgis duration. Handbook for transformation of datums, projections, grids. Understanding datums, coordinate systems and map projections. Relationship and applications of utm projection and gauss. Because utm projection and gausskruger projection have the same character, so there is a similar exchange relation between them. Background on the geographic coordinate system and map. Projected coordinate systems are derived from map projections and geographic coordinate systems from latitude and longitude degrees. In each coordinate system, geodists use mathematics to give each position on earth a unique.
The browse for coordinate system dialog box will appear. The geographic coordinate systems warning box may appear to warn you that the layers geographic. The map of massachusetts in unprojected decimal degrees of longitude and latitude note the proportion of the lines and the circle. Grids rectangular grids have been developed for the use of surveyors. I address this topic because so much visualization is related to the. What it wont do is the geographicdatum transformation part if there are no transformations already set. Presented by john schaeffer juniper gis services, inc. Horizontal coordinate systems locate data across the surface of the earth, and vertical coordinate systems locate the relative height or depth of data. I also intend to reproject on the fly thousands of shape files and rasters. These are often referred to as geographic coordinate systems. Handbook on geographic information systems and digital. With both files in the same projection and coordinate system, you are now ready to do correct overlay analyses. 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. Map projections use cartesian coordinates a projected coordinate system is any coordinate system designed for a flat surface.
Rectangular coordinate system uses x,y coordinates to represent positions on a plane. Cartesian coordinate system using x, y coordinate values 2d, planar surface 4 projection. Useful for locating positions on the curved surface of the earth. In the table of contents, rightclick layers properties, then click the coordinate system tab. The geographic coordinate system great lakes worm watch.
Coordinate systems, projections, and transformations. This powerpoint is available at gis linkspresentations understanding coordinate systems for arcgis 2. Map projection, coordinate system and datum youtube. Within arcgis, every dataset has a coordinate system, which is used to integrate it with other geographic data layers within a common. Coordinate systems either geographic or projected provide a framework for defining realworld locations. 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. Understanding map projections, datums, and 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 earth, and where are things on the earth. The definition of the map projection for projected coordinate systems. 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 difference is that wgs 84 is a geographic coordinate system, and utm is a projected coordinate system. Types of coordinate systems 1 global cartesian coordinates x,y,z for the whole earth 2 geographic coordinates. Grid systems are normally divided into zones so that distortion and variation of scale within any one zone are kept small.
In the select a coordinate system section, expand predefined projected coordinate systems state plane one by one, expand the folders, click a state plane projection file, then click apply. As mentioned above, there are many angular systems with their parameters called shortly datums and many projected systems each based on some datum. Map projections and coordinate systems gis courses. Geographical coordinate system uses latitude and longitude to represent the x,y position in space.
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