GeodesicBuffer(IEnumerable<Geometry>,Double,LinearUnit) Method

In This Topic

Creates buffers at the specified distance around the given geometries. Will union the results of all buffers.

Syntax

C#
Visual Basic (Declaration)

Geometry GeodesicBuffer( 
   IEnumerable<Geometry> geometries,
   double distance,
   LinearUnit distanceUnit
)

Overloads Function GeodesicBuffer( _
   ByVal geometries As IEnumerable(Of Geometry), _
   ByVal distance As Double, _
   ByVal distanceUnit As LinearUnit _
) As Geometry

Parameters

geometries: Specifies the input geometries.
distance: The distance to buffer the geometries.
distanceUnit: The unit of the buffer distance. If null, then the buffer distance is in meters.

Return Value

The polygon that represents the buffered area.

Exceptions

Exception	Description
System.ArgumentNullException	Geometries is null or empty
System.NotImplementedException	The method is not implemented for GeometryBag.
System.ArgumentException	Geometries have no spatial reference.
System.NotImplementedException	The first non-null spatial reference is an image coordinate system.
System.ArgumentException	The buffer distance must be a valid floating point number.

Remarks

At least one geometry must have a spatial reference that is not null or Unknown. The spatial reference of the output geometries is the first valid spatial reference found in the list of geometries. All other geometries are projected to this spatial reference, if necessary. The returned polygon is the union of all the buffered geometries.

If the buffer distance is zero and the input geometry is a polygon or an envelope, then a polygon is created from the input geometries.

If the distance is less than or equal to zero and the input geometry is not a polygon or an envelope, then an empty polygon is created.

Example

Create a buffer polygon at the specified geodesic distance

// buffer a point
MapPoint pt = MapPointBuilderEx.CreateMapPoint(1.0, 1.0, SpatialReferences.WGS84);
Polygon outPolygon = GeometryEngine.Instance.GeodesicBuffer(pt, 5) as Polygon;

double delta = SpatialReferences.WGS84.XYTolerance * 2 * Math.Sqrt(2);
ReadOnlyPointCollection points = outPolygon.Points;
foreach (MapPoint p in points)
{
  double d = GeometryEngine.Instance.GeodesicDistance(pt, p);
  // d = 5 (+- delta)
}

// specify a unit for the distance
outPolygon = GeometryEngine.Instance.GeodesicBuffer(pt, 5000, LinearUnit.Millimeters) as Polygon;

// buffer of 0 distance produces an empty geometry
Geometry g = GeometryEngine.Instance.GeodesicBuffer(pt, 0);
// g.IsEmpty = true

// buffer many points
List<MapPoint> list = new List<MapPoint>();
list.Add(MapPointBuilderEx.CreateMapPoint(1.0, 1.0, SpatialReferences.WGS84));
list.Add(MapPointBuilderEx.CreateMapPoint(10.0, 20.0));
list.Add(MapPointBuilderEx.CreateMapPoint(40.0, 40.0));
list.Add(MapPointBuilderEx.CreateMapPoint(60.0, 60.0));

outPolygon = GeometryEngine.Instance.GeodesicBuffer(list, 10000) as Polygon;
// outPolygon.PartCount = 4

// buffer different geometry types
List<Coordinate2D> coords = new List<Coordinate2D>()
{
  new Coordinate2D(1, 2), new Coordinate2D(10, 20), new Coordinate2D(20, 30),
  new Coordinate2D(50, 60), new Coordinate2D(70, 80), new Coordinate2D(80, 40),
  new Coordinate2D(90, 10), new Coordinate2D(110, 15), new Coordinate2D(120, 30),
  new Coordinate2D(10, 40), new Coordinate2D(-10, 40), new Coordinate2D(-10, 50)
};

List<Geometry> manyGeometries = new List<Geometry>
{
  MapPointBuilderEx.CreateMapPoint(1.0, 1.0, SpatialReferences.WGS84),
  PolylineBuilderEx.CreatePolyline(new List<Coordinate2D>(){coords[0], coords[1], coords[2]}, SpatialReferences.WGS84),
  PolylineBuilderEx.CreatePolyline(new List<Coordinate2D>(){coords[3], coords[4], coords[5]}),
  PolygonBuilderEx.CreatePolygon(new List<Coordinate2D>(){coords[9], coords[10], coords[11]})
};

outPolygon = GeometryEngine.Instance.GeodesicBuffer(manyGeometries, 20000) as Polygon;

// specify unit types
outPolygon = GeometryEngine.Instance.GeodesicBuffer(manyGeometries, 20, LinearUnit.Miles) as Polygon;

Requirements

Target Platforms: Windows 11, Windows 10, Windows 8.1

Reference

IGeometryEngine Interface
IGeometryEngine Members
Overload List

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