public double SemiAxis1Length {get; set;}

{
  GeodesicEllipseParameter param = new()
  {
    AxisDirection = 4 * Math.PI / 3,
    Center = new Coordinate2D(-120, 60),
    LinearUnit = LinearUnit.Meters,
    OutGeometryType = GeometryType.Polyline,
    SemiAxis1Length = 6500000,
    SemiAxis2Length = 1500000,
    VertexCount = 800
  };

  Geometry geometry = GeometryEngine.Instance.GeodesicEllipse(param, SpatialReferences.WGS84);
  // geometry.IsEmpty = false

  polyline = geometry as Polyline;
  // polyline.PointCount = 801
  // polyline.PartCount = 1
}