GeodesicEllipse Method

The function returns a piecewise approximation of a geodesic ellipse (or geodesic circle, if semiAxis1Length = semiAxis2Length). Constructs a geodesic ellipse centered on the specified point. If this method is used to generate a polygon or a polyline, the result may have more than one part, depending on the size of the ellipse and its position relative to the horizon of the coordinate system. When the method generates a polyline or a multipoint, the result vertices lie on the boundary of the ellipse. When a polygon is generated, the interior of the polygon is the interior of the ellipse, however the boundary of the polygon may contain segments from the spatial reference horizon, or from the GCS extent.

Syntax

C#
Visual Basic (Declaration)

Geometry GeodesicEllipse( 
   GeodesicEllipseParameter parameter,
   SpatialReference spatialReference
)

Function GeodesicEllipse( _
   ByVal parameter As GeodesicEllipseParameter, _
   ByVal spatialReference As SpatialReference _
) As Geometry

Parameters

parameter: The geodesic ellipse parameter that describes how to create the geodesic ellipse.
spatialReference

Return Value

The geometry that contains the geodesic ellipse.

Exceptions

Exception	Description
System.NotSupportedException	Only Polygon, Polyline and Multipoint are supported for GeodesicEllipseParameter.OutGeometryType.
System.ArgumentNullException	Either parameteror spatialReference is null.
System.NotImplementedException	The spatial reference is an image coordinate system.

Remarks

If the smaller axis is zero, the ellipse will degenerate to a line segment, a point, or an empty geometry (depending on the larger axis and output type). Otherwise, if VertextCount < 10, the number of vertices will default to 10.

Example

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

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

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

Requirements

Target Platforms: Windows 10, Windows 8.1, Windows 7

Reference

IGeometryEngine Interface
IGeometryEngine Members