anchor.diff:       yChk=zero
        xChk=-xRe
        nChk=xRe
  -  else if(abs(thetaRay/(pi*three/two)-one).lt.c1m6) then ! thetaRay=1.5pi
  +  else if(abs(thetaRay/(pi*(three/two))-one).lt.c1m6) then ! thetaRay=1.5pi
        yChk=-yRe
        xChk=zero
        nChk=yRe
  
positive.code:      else if(pi/two.lt.thetaRay.and.thetaRay.lt.pi) then ! second quadrant
          tmpX0=-abs(x0)
          tmpY0=abs(y0)
       else if(pi.lt.thetaRay.and.thetaRay.lt.pi/two*three) then ! second quadrant
          tmpX0=-abs(x0)
          tmpY0=-abs(y0)
       else ! fourth quadrant
  
negative.code:      delta=-(mRay*tmpX0-tmpY0+qRay)**2+(bb**2+aa**2*mRay**2)
       if(delta.lt.zero) return
       if((zero.lt.thetaRay.and.thetaRay.lt.pi/two).or. & ! first quadrant
   &       (pi*(three/two).lt.thetaRay.and.thetaRay.lt.two*pi)) then ! fourth quadrant
          xChk=((aa**2*(mRay*(tmpY0-qRay))+bb**2*tmpX0)+(aa*bb)*sqrt(delta))/(bb**2+aa**2*mRay**2)
       else
          xChk=((aa**2*(mRay*(tmpY0-qRay))+bb**2*tmpX0)+(-one*(aa*bb))*sqrt(delta))/(bb**2+aa**2*mRay**2)
       end if
       yChk=mRay*xChk+qRay
       nChk=sqrt(xChk**2+yChk**2)
  