anchor.diff:      !--------------------------------------------------------------------------
       ! Earth elevation data
       !--------------------------------------------------------------------------
  -
  -
       subroutine earth_elevation(iunit, alt_table)
           integer :: iunit
           real (kind=8), dimension(nlat_alt*nlon_alt,3), intent(inout) :: alt_table
  -
           integer :: i, j
           character (len=100) :: filename
           character (len=100) :: buffer
  
positive.code: 
          densf = interpol_densf([lat,lon], dens_table, -90._r8, 90._r8, -180._r8, 180._r8, nlat_alt, nlon_alt)
  
  
      end function dens_andes
  
  
  
negative.code:         real (kind=8) :: x1, x2, y1, y2, x0, y0
          real (kind=8) :: dx, dy
  
          dx = (xmax-xmin)/(nx-1)
          dy = (ymax-ymin)/(ny-1)
  
  