GeodesicLength(Geometry) Method

In This Topic

Gets the geodesic length of the input geometry.

Syntax

C#
Visual Basic (Declaration)

public double GeodesicLength( 
   Geometry geometry
)

Public Overloads Function GeodesicLength( _
   ByVal geometry As Geometry _
) As Double

Parameters

geometry: The input geometry. Cannot be null and its spatial reference cannot be null.

Return Value

The calculated geodesic length in meters. If the geometry is empty, then zero is returned.

Exceptions

Exception	Description
System.ArgumentNullException	Geometry is null or geometry's spatial reference is null.
System.NotImplementedException	The method is not implemented for GeometryBag or Multipatch.
System.NotImplementedException	Spatial reference of geometryis an image coordinate system.

Remarks

Geodesic length is calculated by using only the vertices of the geometry and defining the segments between the points as geodesic segments independent of the actual shape of the geometry. A geodesic segment is the shortest path between two points on an ellipsoid. For example, if you have a closed polyline with only two vertices that represents the equator, the length returned will be zero.

Example

Determine geodesic length of a line

var polyline = PolylineBuilderEx.CreatePolyline(new[]
{
    MapPointBuilderEx.CreateMapPoint(-10018754.1713946, 10018754.1713946),
    MapPointBuilderEx.CreateMapPoint(10018754.1713946, 10018754.1713946)
}, SpatialReferences.WebMercator);

var length = GeometryEngine.Instance.GeodesicLength(polyline);
// length is approx 5243784.5551844323 in meters

length = GeometryEngine.Instance.GeodesicLength(polyline, LinearUnit.Miles);
// length is approx 3258.33666089067 in miles

var polyline2 = GeometryEngine.Instance.Project(polyline, SpatialReferences.WGS84);
length = GeometryEngine.Instance.GeodesicLength(polyline2);
// length is approx 5243784.55518443 in meters after projecting

GeodeticDensifyByLength - polygon

List<Coordinate2D> coords = new List<Coordinate2D>()
{
  new Coordinate2D(-80, 0),
  new Coordinate2D(-20, 60),
  new Coordinate2D(40, 20),
  new Coordinate2D(0, -20),
  new Coordinate2D(-80, 0)
};

SpatialReference sr = SpatialReferences.WGS84;

// create a polygon
Polygon polygon = PolygonBuilderEx.CreatePolygon(coords, sr);

// get the geodesic lengths of the polygon segments
ReadOnlySegmentCollection segments = polygon.Parts[0];
List<Double> geoLengths = new List<Double>(segments.Count);
foreach (Segment s in segments)
{
  Polyline line = PolylineBuilderEx.CreatePolyline(s, sr);
  double geoLen = GeometryEngine.Instance.GeodesicLength(line);
  geoLengths.Add(geoLen);
}

// find the max length
geoLengths.Sort();
double maxLen = geoLengths[geoLengths.Count - 1];

// densify the polygon (in meters)
Polygon densifiedPoly = GeometryEngine.Instance.GeodeticDensifyByLength(polygon, maxLen, LinearUnit.Meters, GeodeticCurveType.Geodesic) as Polygon;

// densify the polygon (in km)
double maxSegmentLength = maxLen / 10000;
densifiedPoly = GeometryEngine.Instance.GeodeticDensifyByLength(polygon, maxSegmentLength, LinearUnit.Kilometers, GeodeticCurveType.Geodesic) as Polygon;

Requirements

Target Platforms: Windows 11, Windows 10, Windows 8.1

Reference

GeometryEngine Class
GeometryEngine Members
Overload List

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