anchor.diff:  
   c           # nv has unit length
               do m = 1,3
  -               ytangents(i,j,m) = taup(m)/tlen
  +c               ytangents(i,j,m) = taup(m)/tlen
  +               ytangents(i,j,m) = taup(m)
               enddo
               edge_lengths(i,j,2) = tlen
            enddo
  
positive.code:             tlen = sqrt(taup(1)**2 + taup(2)**2 + taup(3)**2)
  
              DO m = 1,3
                 xtangents(i,j,m) = taup(m)/tlen
              ENDDO
              edge_lengths(i,j,1) = tlen
           ENDDO
  
negative.code:             area(i,j) = sum_area
           enddo
        enddo
  
        end
  
  