# SpatialReference

The spatial reference specifies how geometry coordinates relate to real-world space. Instances of this class represent a specific coordinate system identified by a well-known ID (WKID) number or well-known text (WKT) string. There are two broad classes of coordinate systems:

Geographic coordinate systems use a 3-dimensional spherical surface to define locations on the earth.

Projected coordinate systems use a flat, 2-dimensional surface. See [https://developers.arcgis.com/documentation/spatial-references/] for more information about spatial references.

SpatialReference ensures that you can accurately view, query, and analyze the layers of a GeoModel.

The spatial reference value is available from a map or scene after loading has completed, and is immutable. If you want to set this value for a new map or scene, use the ArcGISMap.ArcGISMap(SpatialReference) or ArcGISScene.ArcGISScene(SceneViewTilingScheme) constructors.

#### Since

200.1.0

## Constructors

Creates a spatial reference based on WKID. The method will create a spatial reference that has only horizontal coordinate system and does not have vertical coordinate system associated with it.

Creates a spatial reference based on WKID for the horizontal coordinate system and vertical coordinate system. The method creates a spatial reference that has both horizontal and vertical coordinate systems. When the vertical WKID is 0, the method is equivalent to calling SpatialReference.SpatialReference(Int), and does not define a vertical coordinate system part.

Creates a spatial reference based on well-known text.

## Types

## Properties

If the given spatial reference is a projected coordinate system, then this returns the geographic coordinate system of that system. If the spatial reference is a projected coordinate system, then a spatial reference object representing the underlying geographic coordinate system is returned. Every projected coordinate system has an underlying geographic coordinate system. If the spatial reference is a geographic coordinate system, then a reference to itself is returned. If the spatial reference is a local spatial reference, a null is returned with an error.

True if spatial reference has a vertical coordinate system set; false otherwise. A spatial reference can optionally include a definition for a vertical coordinate system (VCS), which can be used to interpret the z-values of a geometry. A VCS defines linear units of measure, the origin of z-values, and whether z-values are "positive up" (representing heights above a surface) or "positive down" (indicating that values are depths below a surface).

The unit of measure for the vertical coordinate system of this spatial reference. Is null if SpatialReference.hasVertical is false.

## Functions

Calculate the grid convergence for a spatial reference at a given point. The grid convergence is the angle between True North and Grid North at a point on a map. The grid convergence can be used to convert a horizontal direction expressed as an azimuth in a geographic coordinate system (relative to True North) to a direction expressed as a bearing in a projected coordinate system (relative to Grid North), and vice versa.