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.
| Name | Type | Default | Description |
|---|---|---|---|
ellipsoid |
Ellipsoid |
Ellipsoid.WGS84
|
optional The ellipsoid. |
See:
Members
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 rectangle is equal in the X and Y directions.
The constant value is computed by calling:
WebMercatorProjection.mercatorAngleToGeodeticLatitude(Math.PI)
readonly ellipsoid : Ellipsoid
Gets the
Ellipsoid.
Methods
Converts a geodetic latitude in radians, in the range -PI/2 to PI/2, to a Mercator
angle in the range -PI to PI.
| Name | Type | Description |
|---|---|---|
latitude |
number | The geodetic latitude in radians. |
Returns:
The Mercator angle.
Converts a Mercator angle, in the range -PI to PI, to a geodetic latitude
in the range -PI/2 to PI/2.
| Name | Type | Description |
|---|---|---|
mercatorAngle |
number | The angle to convert. |
Returns:
The geodetic latitude in radians.
project(cartographic, result) → Cartesian3
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.
| Name | Type | 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:
The equivalent web mercator X, Y, Z coordinates, in meters.
unproject(cartesian, result) → Cartographic
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.
| Name | Type | Description |
|---|---|---|
cartesian |
Cartesian3 | The web mercator Cartesian position to unrproject with height (z) in meters. |
result |
Cartographic | optional The instance to which to copy the result, or undefined if a new instance should be created. |
Returns:
The equivalent cartographic coordinates.