code: public static double latitudeToMetersY( double latitude ) {
          return EQUATORIALRADIUS * Math.log(Math.tan(Math.PI / 4 + 0.5 * Math.toRadians(latitude)));
      }
docs: Convert a latitude coordinate (in degrees) to a vertical distance in meters from the
  equator
  
  @param latitude in degrees
  @return latitude in meters in spherical mercator projection