ExtractSector

function ExtractSector(TPA:TPointArray; angle,sector:Double; radLo,radHi:Int32; center:TPoint):TPointArray;
var
  i,j:Int32;
  theta,dist,delta:Double;
begin
  SetLength(Result, Length(TPA));
  angle := Radians(angle);
  for i:=0 to High(TPA) do
  begin
    dist  := Sqrt(Sqr(TPA[i].x-center.x) + Sqr(TPA[i].y-center.y));
    theta := ArcTan2(TPA[i].y-center.y, TPA[i].x-center.x) + (PI / 2);
    delta := Degrees(ArcTan2(Sin(theta-angle), Cos(theta-angle)));
    if (Abs(delta) <= sector) and (dist >= radLo) and (dist <= radHi) then
    begin
      Result[j] := TPA[i];
      Inc(j);
    end;
  end;
  SetLength(Result, j);
end;