anchor.diff:       2                            'lon lat z'
         write(*,*)
        1 '-clip XYFILE           Clip points to lie in interior of ',
  -     2                            'XYFILE (outside points are nan)'
  +     2                            'XYFILE (outside points are -12345)'
         write(*,*)
        1 '-o OFILE               Output to file (default prints to ',
        2              'standard output)'
  
positive.code:       endif
        write(*,*)
       1 'Usage: grid -x X1 X2 [-nx NX|-dx DX] ',
       2            '-y Y1 Y2 [-ny NY|-dy DY] '
        write(*,*)
       1 '            [-z Z|-dip X0 Y0 Z0 STR ',
       2              'DIP|-xsec X0 Y0 AZ [-xz]]'
  
negative.code:           p = 1
        elseif (tag(1:2).eq.'-h') then
            call usage(' ')
        elseif (tag(1:2).eq.'-R') then
            call getarg(i,tag)
            j = index(tag,'-R')
            tag(j:j+1) = ''
            j = index(tag,'/')
            tag(j:j) = ' '
            j = index(tag,'/')
            tag(j:j) = ' '
            j = index(tag,'/')
            tag(j:j) = ' '
            read(tag,*) x1,x2,y1,y2
        else
            call usage('!! Error: no option '//tag)
        endif
  