anchor.diff:        write(*,*)
        1 '-o OFILE               Output to file (default prints to ',
        2              'standard output)'
  +      write(*,*)
  +     1 '-exp x|y               Make grid increment x|y exponential'
  +      write(*,*)
  +     1 '                           nx/ny => equal fraction spacing'
  +      write(*,*)
  +     1 '                           dx/dy => fractional increment'
         write (*,*)
        1 '-p                     Print results to standard output ',
        2                               '(overrides -o)'
  
positive.code: 3         var = (Y(I)*X(J)-X(I)*Y(J))/(X(J)-X(I))
            if (var.lt.0.0d0) then
                goto 2
            elseif (var.eq.0.0d0) then
                goto 4
            else
                goto 5
  
negative.code:       zsave = z
        if (p.eq.0) open(unit=101,file=ofile,status='unknown')
        do 16 i = 0,nx-1
            ! Using equal or fractional spacing?
            if (mod(expflg,10).eq.0) then
                x = x1 + dble(i)*dx
            else
                x = x1
                do 201 k = 1,i
                    x = x*dx
    201         continue
            endif
            if (xsec.eq.1) then
                call dlola(lo,la,ref(1),ref(2),x,ref(3))
            endif
            do 15 j = 0,ny-1
                if (expflg.lt.10) then
                    y = y1 + dble(j)*dy
                else
                    y = y1
                    do 202 k = 1,j
                        y = y*dy
    202             continue
                endif
  C             CALCULATE Z ON DIPPING GRID
                if (ref(5).gt.0.0d0) then
                    call ddistaz(dist,az,ref(1),ref(2),x,y)
  