Getting point from known points to specific distance of polyline using ArcObjects?

Question

I want to know the coordinates of a polyline from specific point and distance. I have attached image to clear the specification. say, I have a points B(2,3). I want to know the coordinates of A and C from 2 feet distance of B point. I have tried this:

public IPoint GetPointAtFrom(double distance, Coordinate givenCoordinate)
    {
        ArcGeometry.IPoint outletPoint = new ArcGeometry.PointClass();
        ArcGeometry.ICurve curve = _polyline;
        curve.QueryPoint(ArcGeometry.esriSegmentExtension.esriExtendTangentAtFrom, distance, false, outletPoint);
        return new Point(outletPoint);
    }

but it gives from point or others.

Any idea? I am using .net in arcgis 10.0

Answer 1

One way would be to use ICurve QueryPointAndDistance to and get the DistanceAlongCurve value for your 'B' point.

Then call ICurve.GetSubcurve twice (with the DistanceAlongCurve + 2 and DistanceAlongCurve - 2) and the fromDistance parameter as 0. And the asRatio as false.

The "To" points of the resulting subcurves would be your 'A' and 'C'.

http://resources.arcgis.com/EN/HELP/ARCOBJECTS-NET/COMPONENTHELP/index.html#/GetSubcurve_Method/002m00000110000000/