Acoordinate systemIt is a frame of reference that defines the location of features in a two- or three-dimensional space. Maps and scenes use coordinate systems to correctly locate and display data on the Earth's surface and in each other. Coordinate systems can be horizontal, which define where features are located around the world, or vertical, which define how high or low features are relative to a surface. Coordinate systems can be defined in maps and scenes.

A map or scene always has a horizontal coordinate system. Optionally, you can also configure avertical coordinate system. In a new blank map or local scene, the default horizontal coordinate system is WGS84 Web Mercator. For global scenes, the default horizontal coordinate system is WGS84. There are many coordinate systems to choose from for local maps and scenes, but the horizontal coordinate system for a global map is limited to WGS84 or China Geodetic Coordinate System 2000 (CGCS 2000). see topicCoalunderstand the differences between local and global scenarios.

Blank maps and scenes derive their coordinate systems from the first layer added. As you add additional layers to a map or scene, they are automatically displayed using the scene's current map or coordinate system. If the geographic coordinate system of the map or scene is different from the geographic coordinate system of the layer, the data is projected in real time using aTransformation.

##### Careful:

Real-time data plotting can take longer and is not recommended when editing data or performing analysis. It is best to make sure that all the data is in the same coordinate system. Use theProjectoProject-RasterTool for projecting spatial data from one coordinate system to another.

Complete the following steps to select or import a coordinate system or you cancreate a coordinate systeminstead of that.

## Define the coordinate system

You can define the coordinate system of a map or scene directly, you can define it from a layer in the map or scene, or you can define it from another data source.

#### Choose a coordinate system from a list

Follow these steps to define the coordinate system directly, choosing one from a list:

- Nocard propertiesIn the dialog box, click the buttoncoordinate systemAba.
The buttons below theXY actualmiZ actualTitles show the current horizontal and vertical coordinate systems of the map or scene. Cannot define a vertical coordinate system. Clickdetailsfor each coordinate system to see how they are defined.

- To change the horizontal or vertical coordinate system, click the button below theXY actualoZ actualOrientation o Select a suitable coordinate system from the correspondingavailable coordinate systemsList.
- To get more information about a coordinate system, right-click on it and click on it in the listdetails to display the coordinate system parameters. The valid application area for each coordinate system is indicated in the details list and also visually as a blue rectangle on the map at the bottom of the dialog window. If the area is too small, it may simply appear as a circular dot.
- Optionally, search for coordinate systems. Enter a search term in thisLook forto find a specific coordinate system.
- Optionally, filter the list of coordinate systems. squeezeSpatial FilterI likeand clickDefine spatial filter . NoSpatial Filter Indexdialog, selectData scope in all layersocustom extension. Calculate a custom extent of a layer on the map or define an exact numeric extent.

- CliqueOKDefine and close the coordinate systemcard propertiesdialog box.

#### Specify the coordinate system of a layer

Follow these steps to define a coordinate system for a map or scene from a layer it contains. This is recommended to ensure that all layers in a map use the same coordinate system.

- Nocard propertiesIn the dialog box, click the buttoncoordinate systemAba.
- Underavailable coordinate systemsenumerate, expandTo her. Expand the title of a coordinate system to see the layers that reference it.
- To set the coordinate system of another data source, clickadd coordinate systemI likeand clickimport coordinate system . Navigate to a data source (or a previously saved fileprjfile) defined with the coordinate system you want to use. You can then add the coordinate system to yourfavoritesready to make them available for all your projects.
- CliqueOKDefine and close the coordinate systemcard propertiesdialog box.

#### Set the coordinate system of a data source

To define a coordinate system from a data source, do the following:

- I amContentIn the panel, right-click the map or scene and clickCharacteristics.
- Nocard propertiesIn the dialog box, click the buttoncoordinate systemAba.
- squeezeadd coordinate systemI likeand clickimport coordinate system . Navigate to a data source (or a previously saved fileprjfile) defined with the coordinate system you want to use.
- CliqueOKDefine and close the coordinate systemcard propertiesdialog box.

## save coordinate systems

If you frequently use coordinate systems in your projects, you can add them to your listfavoritesto find them more easily. Favorites are available in all your projects. You can also save each coordinate system as a projection file (prjfile extension). Projection files can be used to define a coordinate system in geoprocessing.

#### Save a coordinate system as a favorite

Follow these steps to save a coordinate system as a favorite:

- Nocard propertiesIn the dialog box, click the buttoncoordinate systemAba.
- Right-click on a coordinate system in theavailable coordinate systemslist and clickAdd to favorites so that the coordinate system is displayed below thefavoritesTitle on this listing for easy reference.

#### Save a coordinate system as a projection file

Follow these steps to save a coordinate system as a projection file:

- Nocard propertiesIn the dialog box, click the buttoncoordinate systemAba.
- Right-click on a coordinate system in theavailable coordinate systemsList.
- CliqueSave as projection file .
- NoSave coordinate system as PRJ fileIn the dialog, browse to a location on your file system and enter a file name.
The default location to save the projection file is the Favorites folder, located in[Install Drive]:\Users\[Your Name]\AppData\Local\ESRI\ArcGISPro\Favorites. If you save to this folder, the coordinate system you saved to a projection file will appear in thefavoritessection inavailable coordinate systemslist notcard propertiesdialog box.

## Working with vertical coordinate systems

Maps and scenes must have a defined horizontal coordinate system, but a vertical coordinate system is optional. To specify an elliptical vertical coordinate system, it must have the same data as the horizontal coordinate system. The datum name, spheroid name, and all spheroid properties of the two coordinate systems must match exactly.

If the current horizontal coordinate system is not compatible with the current vertical coordinate system, follow these steps to select compatible pairs of horizontal and vertical coordinate systems:

- Click the button below thatZ actualtitle and selectnoneof the list.
- Click the button below thatXY actualAddress and select a coordinate system from the list with data that corresponds to the elliptical vertical coordinate system you need.
To view the datum of a coordinate system, right-click in the list and clickdetails .

- Click the button below thatZ actualDirection and choose an elliptical vertical coordinate system with the same datum.

#### Related topics

- Coordinate systems, map projections and transformations
- Geographic Date Transformations
- Vertical coordinate systems
- Define a new coordinate system
- Allow panning on the international date line on maps

Comments on this topic?