function WebMercatorProjection(ellipsoid) {
  this._ellipsoid = ellipsoid ?? Ellipsoid.WGS84;
  this._semimajorAxis = this._ellipsoid.maximumRadius;
  this._oneOverSemimajorAxis = 1.0 / this._semimajorAxis;
}
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.

@alias WebMercatorProjection
@constructor

@param {Ellipsoid} [ellipsoid=Ellipsoid.WGS84] The ellipsoid.

@see GeographicProjection