WebMercatorProjection

WebMercatorProjection

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The map projection used by Google Maps, Bing Maps, and most of ArcGIS Online, EPSG:3857. This projection use longitude and latitude expressed with the WGS84 and transforms them to Mercator using the spherical (rather than ellipsoidal) equations.

Parameters:
Name Type Argument Default Description
ellipsoid Ellipsoid <optional>
Ellipsoid.WGS84 The ellipsoid.
See:
Source:

Members

<static> :Number

The maximum latitude (both North and South) supported by a Web Mercator (EPSG:3857) projection. Technically, the Mercator projection is defined for any latitude up to (but not including) 90 degrees, but it makes sense to cut it off sooner because it grows exponentially with increasing latitude. The logic behind this particular cutoff value, which is the one used by Google Maps, Bing Maps, and Esri, is that it makes the projection square. That is, the extent is equal in the X and Y directions. The constant value is computed by calling: WebMercatorProjection.mercatorAngleToGeodeticLatitude(Math.PI)

Methods

Gets the Ellipsoid.

Returns:
Ellipsoid The ellipsoid.

Converts geodetic ellipsoid coordinates, in radians, to the equivalent Web Mercator X, Y, Z coordinates expressed in meters and returned in a Cartesian3. The height is copied unmodified to the Z coordinate.

Parameters:
Name Type Argument Description
cartographic Cartographic The cartographic coordinates in radians.
result Cartesian3 <optional>
The instance to which to copy the result, or undefined if a new instance should be created.
Returns:
Cartesian3 The equivalent web mercator X, Y, Z coordinates, in meters.

Converts Web Mercator X, Y coordinates, expressed in meters, to a Cartographic containing geodetic ellipsoid coordinates. The Z coordinate is copied unmodified to the height.

Parameters:
Name Type Argument Description
cartesian Cartesian2 The web mercator coordinates in meters.
result Cartographic <optional>
The instance to which to copy the result, or undefined if a new instance should be created.
Returns:
Cartographic The equivalent cartographic coordinates.

<static>

Converts a geodetic latitude in radians, in the range -PI/2 to PI/2, to a Mercator angle in the range -PI to PI.

Parameters:
Name Type Description
latitude Number The geodetic latitude in radians.
Returns:
Number The Mercator angle.

<static>

Converts a Mercator angle, in the range -PI to PI, to a geodetic latitude in the range -PI/2 to PI/2.

Parameters:
Name Type Description
mercatorAngle Number The angle to convert.
Returns:
Number The geodetic latitude in radians.