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Change coordinate system in arcmap11/7/2022 For example, if z-value height is defined in NAD 1983, the geographic coordinate system must be defined in NAD 1983 also, not WGS84. When you use an ellipsoidal vertical coordinate system, you must ensure that it matches the geographic coordinate system. For example, a stream in a large-scale map may appear to flow in an uphill direction using an ellipsoidal vertical coordinate system. Since they are calculated on a mathematical model, they are simpler than gravity-based vertical coordinate systems, but they may lack significant accuracy, especially in large-scale applications. Ellipsoidal coordinate systems are based on a reference to a mathematically derived spheroidal or ellipsoidal volumetric surface. With this type, the reference surface is defined by a mean sea level calculation (or, in some cases, it is derived from the level of a single point). Gravity-based vertical coordinate systems are more commonly used. There are two types of vertical coordinate systems. Vertical coordinate systems are not applied by default to new maps and scenes you must explicitly choose one. Using a vertical coordinate system improves locational accuracy in analysis and editing. Vertical coordinate systems are always in linear units such as meters or feet. Vertical coordinate systems provide a reference for z-coordinates, which are measurements of the height or depth of features. The map projection contains the mathematical calculations that convert the geodetic locations to the planar system. A projected coordinate system is based on a geographic coordinate system and a map projection. A projected coordinate system is a planar system that uses two-dimensional coordinates and linear distance measurements as units. A geographic coordinate system is based on a three-dimensional ellipsoidal or spherical surface, and locations are defined using angular measurements, usually degrees of longitude and latitude. Horizontal coordinate systems are either geographic or projected. On the Layer Properties dialog box, click the Source tab and expand the Spatial Reference group. To see the coordinate system defined for your data source, or if your data source has a coordinate system defined, right-click the layer in the Contents pane and click Properties. Use the Project or Project Raster tool to project spatial data from one coordinate system to another.įollow the steps in this topic to specify a coordinate system, or create a coordinate system. It is better to ensure that all the data is in the same coordinate system. Be aware, however, that projecting in real time can take longer to draw and is not advisable if you are editing data or performing analysis. If the map or scene's geographic coordinate system is different than the geographic coordinate system of the layer, the data is projected in real time using a transformation. When you add more layers to a map or scene, they are automatically displayed using the same coordinate system of the map or scene. You can, optionally, define a vertical coordinate system for a map or scene.Įmpty maps and scenes derive their coordinate systems from the first layer added to them. A map or scene always has a horizontal coordinate system. There are numerous coordinate systems to choose from for maps and local scenes, but the horizontal coordinate system for a global scene is limited to either WGS84 or China Geodetic Coordinate System 2000 (CGCS 2000). For global scenes, the default horizontal coordinate system is WGS84. In a new, empty map or local scene, the default horizontal coordinate system is WGS84 Web Mercator. Coordinate systems can be defined in both maps and scenes. 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. A coordinate system is a reference framework that defines the position of features in either two- or three-dimensional space. Maps and scenes use coordinate systems to locate and display data correctly on the earth's surface and relative to one another.
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