To correctly align a feature layer with an image layer in arcview. Map projection, coordinate system and datum youtube. A map projection is a rigorous mathematical means of translating a particular region of our earths curvaceous threedimensional surface into a flat twodimensional representation. Coordinate systems, map projections, and geographic datum. There are many different coordinate systems, based on a variety of geodetic datums, projections, and units in use geographic coordinate systems no projection. Refer to steps for warping raster images scaling a raster image files without a tfw file the following table shows how a raster map without a world file can be manually set to scale. Just as all maps have a map scale, all maps have locations, too. System spcs parameters or to create and employ supplemental plane coordinate projections. Coordinate systems enable geographic datasets to use common locations for integration. Thematic mapping using countries and us states as an example, map projections, coordinate systems, data classi. Understanding projections and coordinate systems important knowledge to have, especially if you deal with many different sets of data that come from different sources.
Map projections and coordinate systems, page 1 synoptic. A coordinate system, datum, and map projection are all components of. Geodesy, projections, and coordinate systems 117 surface figure 331. Map projections and coordinate systems gis courses. The previous specification 2008 allowed for the use of alternative coordinates systems, but this was removed because of interoperability issues. Within or on top of the projection is a coordinate system containing the x and y location values, which incorporates the ellipsoid shape of the earth, datum known base values, and units e. Projected coordinate systems are sometimes referred to as map projections. A tutorial on map projections and geographic coordinate systems. The earth exists in threedimensions but, other than globes, most representations of the earth are two dimensional. Map projection, coordinate system and datum content writer. Resources for further study are presented on page 23. Spheroid or ellipsoid based systems, local systems. In the translation from a spherical surface to a twodimensional, flat surface, a.
The definition of the map projection for projected coordinate systems. The main difference is that projected, geodetic coordinates are cartesian coordinates with two equally scaled orthogonal axes. Coordinate systems either geographic or projected provide a framework for defining realworld locations. The earth is almost spherical, however there is a tiny bulge at. 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. Teaching about coordinate systems is an excellent means of. In north america, if your dataset has an x or ycoordinate with 6, 7, or 8 digits to the left of the decimal point, then your coordinate system is projected most likely to the state plane or utm coordinate systems. Commonly used projections and coordinate systems in bc are utm and bc albers. Continue working your way through to the world folder plain world, not spherebased. Some basic ideas about the mathematics of map projections. Coordinate systems are referenced to the physical earth surface through the use of datums. Coordinate systems can be horizontal, defining where features are across the globe, or vertical, defining how high or deep features are relative to a surface.
Once the file is returned to the work area it can be warped to fit the existing cad work. A coordinate system is a reference framework that defines the position of features in either two or threedimensional space. For instance, in geometry we use x horizontal and y vertical coordinates to define points on a twodimensional plane. Working with map projections and coordinate systems in arcgis. Project the globe onto a 2d surface there are lots of. A gcs is often incorrectly called a datum, but a datum is only one part of a gcs. A map projection is a systematic rendering of locations from the curved earth surface onto a flat. Coordinate systems, projections, and transformations. Map projections summary projections specify a twodimensional coordinate system from a 3d globe all projections cause some distortion errors are controlled by choosing the proper projection type, limiting the area applied there are standard projections. 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. Coordinate systems can be defined in both maps and scenes.
Map projections and coordinate systems university of. The term predefined refers to various coordinate systems that have been preprogrammed into arcmap. Area of use values are in decimal degrees based upon wgs 1984. Understanding projections and coordinate systems important knowledge to have, especially if you deal with many different sets of. In the latest geojson specification 2016, the coordinate reference system for all coordinates is a geographic coordinate reference systemusing the world geodetic system 1984 wgs 84 datumwith longitude and latitude units of decimal degrees. Working with map projections and coordinate systems in. 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. Find a coordinate system and get position on a map. Coordinate systems and map projections provide information for locating data on the earth georeferencing. The process of projection involves distorition of area, distance, shape, and angles. For a conceptual overview, see georeferencing and coordinate systems. This is changing somewhat as more data are collected by gps. Conceptual summary of projections aa coo d ate syste sn coordinate systems xy coordinatesderived via projection from latlong t iti 2 dfl t lines of latitude and longituderepresent position on 2d flat map surface spheroid. 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.
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. Note that it is possible to map data without having defined a coordinate system. The process of converting a threedimensional space to a twodimensional map is called projection. Spatial data has coordinate systems, geographic coordinate systems, or projected coordinate systems defined. 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. Gis positional data are primarily printed maps which have been digitized. Geographic coordinate system uses 3d spherical surface to define locations often incorrectly called a datum includes angular unit of measure, prime meridian and datum point referenced by longitudelatitude angles measured by degrees. The map of massachusetts in unprojected decimal degrees of longitude and latitude note the proportion of the lines and the circle. 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. To adjust errors which occur at map digitization due to distortion of the map measured, 6.
Datums and map projections for remote sensing, gis and surveying, 2nd edition. There is more about map projections probability density function pdf matlab and the national grid in section 7. Page 79 discuss map scale and the basics of coordinate systems. Geodesy, coordinate systems, objectives and map projections.
Ellipsoidal coordinate systems reference a mathematically derived spheroidal or ellipsoidal volumetric surface. The appearance, classification and naming of map projections. Under related information below, click the link titled projections table 2009 to access. Coordinate systems frameworks used to determine position on the surface of the earth. Section 31 and appendix g of the djuric weather analysis textbook. 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. A rewritten and expanded practical guide to coordinate reference systems. A list of common projections for the world will be given.
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. That new file can be used to define or project other data sets. Data in a geographic coordinate system is referenced using latitude and. Objectives coordinate systems and map projections for gis. Two basic types of coordinate systems exist for geographic data. To transform different map projections of many gis data sources to an unified map projection in a gis database, 5. Geo327g386g lab 2 map projections and coordinate systems. Page 22 covers use of map projections in group display. Specify a coordinate systemproperties of maps arcgis pro. Learning the basic properties and uses of coordinate systems understanding the difference between geographic coordinates and projected coordinates getting familiar with different types of map projections managing and troubleshooting coordinate systems of feature classes and images. Projected coordinate systems are derived from map projections and geographic coordinate systems from latitude and longitude degrees. Defining a coordinate system updates the metadata onlydoesnt affect the coordinate valuesdefine data in its current coordinate system, then project add xy data tool uses the maps coordinate system by default exporting a layer in arcmap using the data frames coordinate systemsame as using the project or project raster tools utm n and s.
Coordinate systems and map projections 2nd edition. Map projections are introduced on pages 1012, and pages 19 present some widely used examples. Select a suitable map projection or coordinate system. Lecture 2 map projections and gis coordinate systems. Download the list of supported geographic and vertical coordinate systems. It is impossible to flatten a round object without distortion, and this results in tradeoffs between area. Projections transformation of curved earth to a flat map.
All mapping and coordinate systems are based on this shape. Tutorial 2 exploring map projections and grid systems in. A projected coordinate system pcs, is composed of a datum e. This pdf file lists map projections supported in arcgis desktop version 10. The employed plane coordinate system is either projected or geographic. 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. A geographic coordinate system uses a three dimensional sphere to locate data on the earth. 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. Several common projected coordinate systems are discussed on pages 2021. A gcs includes an angular unit of measure, a prime meridian, and a datum based on a.
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