AGSSpatialReference Class Reference

Description

Represents the spatial reference of a geometry.

A spatial reference determines how map coordinates, or the x,y,z-coordinates in the vertices of geometries, correspond to locations in real-world space. Therefore, it is very important to associate geometries representing spatial data with corresponding spatial references.

Each spatial reference can be represented by either a well-known ID (WKID), or a well-known text (WKT). Spatial references define the spatial properties of a geometry, for instance the coordinate system it uses. There are 2 broad classes of coordinate systems - Geographic & Projected. A Geographic Coordinate system uses a 3-dimensional spherical surface to define locations on the earth. A Projected Coordinate system on the other hand uses a flat, 2-dimensional surface.

Learn more about coordinate systems

Since

100

See also

AGSGeometry for geometry types

+ projectGeometry:toSpatialReference: (AGSGeometryEngine) to project geometries from one spatial reference to another

Inheritance diagram for AGSSpatialReference:

Instance Methods
(double)	- convergenceAngleWithPoint:
(nullable instancetype)	- initWithWKID:
(nullable instancetype)	- initWithWKID:verticalWKID:
(nullable instancetype)	- initWithWKText:
(BOOL)	- isEqualToSpatialReference:
(nullable id)	- toJSON:

Class Methods
(nullable id< AGSJSONSerializable >)	+ fromJSON:error:
(nullable instancetype)	+ spatialReferenceWithWKID:
(nullable instancetype)	+ spatialReferenceWithWKID:verticalWKID:
(nullable instancetype)	+ spatialReferenceWithWKText:
(AGSSpatialReference *)	+ webMercator
(AGSSpatialReference *)	+ WGS84

Properties
AGSSpatialReference *	baseGeographic
BOOL	geographic
BOOL	hasVertical
BOOL	pannable
BOOL	projected
AGSUnit *	unit
NSDictionary< NSString *, id > *	unknownJSON
NSDictionary< NSString *, id > *	unsupportedJSON
AGSLinearUnit *	verticalUnit
NSInteger	verticalWKID
NSInteger	WKID
NSString *	WKText

Method Documentation

convergenceAngleWithPoint:

- (double) convergenceAngleWithPoint:

(AGSPoint *)

point

Calculate the grid convergence for a spatial reference at a given point.

Remarks

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.

Sign convention

The grid convergence returned by this method is positive when Grid North lies east of True North. The following formula demonstrates how to obtain a bearing (b) from an azimuth (a) using the grid convergence (c) returned by this method: b = a - c.

This sign convention is sometimes named the Gauss-Bomford convention.

Other Notes

• Returns 0 if the spatial reference is a geographic coordinate system
• Returns NAN if the point is outside the projection's horizon or on error
• If the point has no spatial reference, it is assumed to be in the given spatial reference
• If the point's spatial reference differs from the spatial reference given, its location will be transformed automatically to the given spatial reference

  Parameters

  point

  The point at which to calculate the convergence angle.

  Returns

  The grid convergence in degrees.

  Since

  100.3

fromJSON:error:

+ (nullable id<AGSJSONSerializable>) fromJSON: (id)  JSONObject error: (NSError **)  error

staticrequiredinherited

Initializes and returns an object from its JSON representation.

Parameters

JSONObject	NSDictionary or NSArray containing the JSON.
error	encountered during the operation, if any.

Since

100

initWithWKID:

- (nullable instancetype) initWithWKID:

(NSInteger)

WKID

Creates a spatial reference with the given well-known ID (WKID).

Parameters

WKID	The well-known ID.

Since

100

initWithWKID:verticalWKID:

- (nullable instancetype) initWithWKID:		(NSInteger)	WKID
verticalWKID:		(NSInteger)	verticalWKID

Creates a spatial reference with the given well-known ID (WKID) and a vertical well-known ID.

Since

100

initWithWKText:

- (nullable instancetype) initWithWKText:

(NSString *)

WKText

Creates a spatial reference with the given well-known text (WKT).

Parameters

WKText

The well-known text.

Since

100

isEqualToSpatialReference:

- (BOOL) isEqualToSpatialReference:

(AGSSpatialReference *)

other

Compares whether two spatial references are equal. They are equal if they have the same WKID or #WKT.

Parameters

other

The other spatial reference to compare this one to.

Returns

YES if the spatial references are equal.

Since

100

spatialReferenceWithWKID:

+ (nullable instancetype) spatialReferenceWithWKID:

(NSInteger)

WKID

Creates a spatial reference with the given well-known ID (WKID).

Parameters

WKID	The well-known ID

Returns

A new spatial reference object.

Since

100

spatialReferenceWithWKID:verticalWKID:

+ (nullable instancetype) spatialReferenceWithWKID:		(NSInteger)	WKID
verticalWKID:		(NSInteger)	verticalWKID

Creates a spatial reference with the given well-known ID (WKID) and a vertical well-known ID.

Parameters

WKID	The well-known ID of the horizontal coordinate system. Must be a positive value.
verticalWKID	The well-known ID of the vertical coordinate system. Must be a non negative value.

Returns

A new spatial reference object.

Since

100

spatialReferenceWithWKText:

+ (nullable instancetype) spatialReferenceWithWKText:

(NSString *)

WKText

Creates a spatial reference with the given well-known text (WKT).

Parameters

WKText

The well-known text

Returns

A new spatial reference object.

Since

100

toJSON:

- (nullable id) toJSON: (NSError **)  error

requiredinherited

Returns JSON representation for this object.

Parameters

error

encountered during the operation, if any.

Returns

NSDictionary or NSArray containing the JSON.

Since

100

Reimplemented in AGSPortalItem.

webMercator

+ (AGSSpatialReference*) webMercator

A spatial reference representing the Web Mercator coordinate system (WKID:3857, equivalent to WKID:102113).

Since

100

WGS84

+ (AGSSpatialReference*) WGS84

A spatial reference representing the WGS84 coordinate system (WKID:4326).

Since

100

Property Documentation

baseGeographic

- (AGSSpatialReference*) baseGeographic

readnonatomicstrong

If the given spatial reference is a projected coordinate system, then this will return 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 nil is returned.

Since

100.0

geographic

- (BOOL) geographic

readnonatomicassign

YES if spatial reference is a Geographic Coordinate System.

Since

100.0

hasVertical

- (BOOL) hasVertical

readnonatomicassign

YES if spatial reference has a vertical coordinate system set; NO 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).

An AGSSpatialReference may have a VCS set, for example by calling the initWithWKID:verticalWKID: constructor. AGSSpatialReference::verticalWKID and AGSSpatialReference::WKText provide more information about the specific VCS set on this instance.

VCSs are used when projecting geometries using an AGSHorizontalVerticalTransformation.

See also

AGSSpatialReference::verticalWKID, AGSSpatialReference::verticalUnit

Since

100.9

pannable

- (BOOL) pannable

readnonatomicassign

YES if coordinate system is horizontally pannable.

Since

100.0

projected

- (BOOL) projected

readnonatomicassign

YES if spatial reference is a Projected Coordinate System.

Since

100.0

unit

- (AGSUnit*) unit

readnonatomicstrong

The unit of measure for the horizontal coordinate system of this spatial reference.

Since

100

unknownJSON

- (NSDictionary<NSString*,id>*) unknownJSON

readrequirednonatomiccopyinherited

A dictionary of values that was in the source JSON but was unparsed by API.

Returns

NSDictionary containing the unknown JSON.

Since

100

unsupportedJSON

- (NSDictionary<NSString*,id>*) unsupportedJSON

readnonatomiccopyinherited

A dictionary of values that are supported by the REST API, but not exposed through the SDK API.

Returns

NSDictionary containing the unsupported JSON.

Since

100

verticalUnit

- (AGSLinearUnit*) verticalUnit

readnonatomicstrong

The unit of measure for the vertical coordinate system of this spatial reference.

Is nil if the AGSSpatialReference::hasVertical property is NO.

Since

100.14

verticalWKID

- (NSInteger) verticalWKID

readnonatomicassign

The well-known ID for the vertical coordinate system.

The well-known ID for the vertical coordinate system (VCS) set on this AGSSpatialReference.

Returns 0 if there is no VCS set, if there is a custom VCS set.

See also

- initWithWKID:verticalWKID:

Since

100.0

WKID

- (NSInteger) WKID

readnonatomicassign

The well-known ID for the horizontal coordinate system.

The well-known ID for the horizontal coordinate system. Will return 0 if an error occurs.

Since

100

WKText

- (NSString*) WKText

readnonatomiccopy

The well-known text of the spatial reference.

Since

100