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I am able to draw the circle but I want a circle of radius 3 kms

I have checked all the previous posts.

I want to know what is the units of radius in the below code.

var radius, circle, ring, pts, angle;
var currentPoint = new esri.geometry.Point(longitude, latitude, this.parent.esriMap.spatialReference);

currentPoint = esri.geometry.geographicToWebMercator(currentPoint);
circle = new esri.geometry.Polygon(this.parent.esriMap.spatialReference);

ring = []; // point that make up the circle 
pts = 40; // number of points on the circle 
angle = 360 / pts; // used to compute points on the circle 

for (var i = 0; i <= 360; i = i + 10) {
    var radian = i * (Math.PI / 180.0);
    var x1= radius * Math.cos(radian);
    var y1= radius * Math.sin(radian);
    var circlePoint = new esri.geometry.Point(x1, y1, this.parent.esriMap.spatialReference);
    circlePoint = esri.geometry.geographicToWebMercator(circlePoint);

    points[i] = new esri.geometry.Point(
        parseFloat(circlePoint.x) + parseFloat(currentPoint.x), parseFloat(circlePoint.y) + parseFloat(currentPoint.y),
        this.parent.esriMap.spatialReference);
    ring.push(points[i]);
}
circle.addRing(ring);
//rest code to add the layers to map
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2 Answers 2

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Creating a 3km radius circle is quite easy in ArcGIS Desktop:

  1. Create a point featureclass marking the center of your area of interest.
  2. Use the Buffer (Analysis) tool to create the 3km radius buffer around the point featureclass.

enter image description here

2

When solving it programmatically I would start with this Snippet from ESRI:

Create Graphic Buffers around Selected Features Snippet:

///<summary>Draws graphic buffers around the selected features in the map using distance units specified.</summary>
///
///<param name="activeView">An IActiveView interface.</param>
///<param name="distance">A System.Double that is the distance in map units around the select features to draw a graphic buffer. Example: 10</param>
/// 
///<remarks></remarks>
public void CreateGraphicBuffersAroundSelectedFeatures(ESRI.ArcGIS.Carto.IActiveView activeView, System.Double distance)
{
  //parameter check
  if (activeView == null || distance < 0)
  {
    return;
  }
  ESRI.ArcGIS.Carto.IMap map = activeView.FocusMap;
  // Clear any previous buffers from the screen
  ESRI.ArcGIS.Carto.IGraphicsContainer graphicsContainer = (ESRI.ArcGIS.Carto.IGraphicsContainer)map; // Explicit Cast
  graphicsContainer.DeleteAllElements();

  // Verify there is a feature(s) selected
  if (map.SelectionCount == 0)
  {
    return;
  }

  // Reset to the first selected feature
  ESRI.ArcGIS.Geodatabase.IEnumFeature enumFeature = (ESRI.ArcGIS.Geodatabase.IEnumFeature)map.FeatureSelection; // Explicit Cast
  enumFeature.Reset();
  ESRI.ArcGIS.Geodatabase.IFeature feature = enumFeature.Next();

  // Buffer all the selected features by the buffer distance and create a new polygon element from each result
  ESRI.ArcGIS.Geometry.ITopologicalOperator topologicalOperator;
  ESRI.ArcGIS.Carto.IElement element;
  while (!(feature == null))
  {
    topologicalOperator = (ESRI.ArcGIS.Geometry.ITopologicalOperator)feature.Shape; // Explicit Cast
    element = new ESRI.ArcGIS.Carto.PolygonElementClass();
    element.Geometry = topologicalOperator.Buffer(distance);
    graphicsContainer.AddElement(element, 0);
    feature = enumFeature.Next();
  }

  activeView.PartialRefresh(ESRI.ArcGIS.Carto.esriViewDrawPhase.esriViewGraphics, null, null);
}

available at: http://help.arcgis.com/en/sdk/10.0/arcobjects_net/componenthelp/index.html#//0049000000n3000000

this takes a feature point geometry as input but you could create your own geometry with the coordinates of the buffer you want to draw. The distance is in map units but following site might help you get the relation to the geographic distance:

ArcGis Desktop Help: About setting distance units

http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=About_setting_distance_units

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