WebMercatorProjection

Members

ellipsoid :Ellipsoid

Gets the Ellipsoid.

<static> MaximumLatitude :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

project

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.

unproject

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> geodeticLatitudeToMercatorAngle

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> mercatorAngleToGeodeticLatitude

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.