   <chapter id="Data_Filters">
      <title>Data Filters</title>
      <para> GPSBabel supports data filtering.  Data filters are
      invoked from the command line via the '-x' option.  It should be
      noted that data filters are invoked in the internal pipeline at
      the point that corresponds to their position on the
      command. This implies that specifying a filter before reading
      any data ('-x &lt;filter&gt; -f &lt;file&gt;'), despite being
      legal, will not have any effect. The advantage is that filters
      can be used intermittently between several variations of input
      and output functions.  It should also be noted that filtering
      data from different input types can sometimes produce
      undesirable results due to differences in the native data
      formats.
</para>
      <para> Beware that most filters only apply to a certain kind of
      data. This is usually indicated below by referring to points,
      tracks or routes in the first sentence which describes each
      filter or in the table at <ulink url="http://www.gpsbabel.org/capabilities.html">gpsbabel.org</ulink>
      .
</para>
     &filters;
     </chapter>
