anchor.diff:        endif
         write(*,*)
        1 'Usage: grid -x X1 X2 [-nx NX|-dx DX] ',
  -     2            '-y Y1 Y2 [-ny NY|-dy DY] '
  +     2            '-y Y1 Y2 [-ny NY|-dy DY] -RX1/X2/Y1/Y2'
         write(*,*)
        1 '            [-z Z|-dip X0 Y0 Z0 STR ',
        2              'DIP|-xsec X0 Y0 AZ [-xz]]'
  
positive.code:           p = 1
        elseif (tag(1:2).eq.'-h') then
            call usage(' ')
        else
            call usage('!! Error: no option '//tag)
        endif
  
negative.code:      2                            'lon lat z'
        write(*,*)
       1 '-clip XYFILE           Clip points to lie in interior of ',
       2                            'XYFILE (outside points are -12345)'
        write(*,*)
       1 '-o OFILE               Output to file (default prints to ',
       2              'standard output)'
  