根据坐标、半径和方向角，计算圆弧边缘中心顶点坐标的算法

function DegToRad(const Degrees: Extended): Extended;  { Radians := Degrees * PI / 180 }

begin

 Result := Degrees * (PI / 180);

end;

procedure DPtoVP(dx, dy: Double; var vX, vY: integer);

begin

 // FViewArea即可视区域的范围，主要用到其坐标范围

 vX := Trunc((dx - FViewArea.Left) / Scale);

 if(FCoordKind = csLeftHand) then

               vY := Trunc((dy - FViewArea.Top)/Scale)

       else

               vY := Trunc((FViewArea.Top - dy) / Scale);

 end;

function GetCellCenterInfo(const AGisX: TGisX; dX, dY: Double;

const AntLength: Integer; const Azimuth: Double): TPoint;

{

获取扇形上弧线中心顶点，结果为屏幕坐标

}

const

 CDOriginAngle = Pi / 2;

 CD360Angle = Pi + Pi;

var

 rAngle: Double;

begin

 Result.X := CIInvalid;

 Result.Y := CIInvalid;

 if not Assigned(AGisX) then Exit;

 if (dX < -180) or (dX > 180) then Exit;

 if (dY < -90) or (dY > 90) then Exit;

 //将经纬度转换为屏幕坐标

 AGisX.ViewPort.GeoCoordSys.ConvertForword(dX, dY, dX, dY);

// 平面坐标转换成屏幕坐标

 DPtoVP(dX, dY, Result.X, Result.Y);

 rAngle := CDOriginAngle - DegToRad(Azimuth);

 if rAngle < 0 then rAngle := rAngle + CD360Angle;

 Result.x := Result.x + Trunc(AntLength * Cos(rAngle));

 //由于屏幕坐标Y坐标是向下的，所以下面减法

 Result.y := Result.y - Trunc(AntLength * Sin(rAngle));

end;

function GetCellCenterInfo(const dX, dY: Double;

const AntLength: Integer; const Azimuth: Double): TPoint2DX;

{

获取扇形上弧线中心顶点，结果为经纬度

}

const

 CDOriginAngle = Pi / 2;

 CD360Angle = Pi + Pi;

var

 rAngle: Double;

begin

 Result.X := CIInvalid;

 Result.Y := CIInvalid;

 if (dX < -180) or (dX > 180) then Exit;

 if (dY < -90) or (dY > 90) then Exit;

 rAngle := CDOriginAngle - DegToRad(Azimuth);

 if rAngle < 0 then rAngle := rAngle + CD360Angle;

 Result.x := dX + AntLength * Cos(rAngle);

 Result.y := dY + AntLength * Sin(rAngle);

end;