+<para>
This option drops waypoints with an altitude higher than the specified value (in meters). See elemin for an explanation why this may be useful.
+</para>
+<para>
This option drops waypoints with an altitude lower than the specified
value (in meters). Although GPS altitude isn't very accurate,
GPS devices may log faulty waypoints from time to time, such as when
near tall buildings. Elevation values that are way off may signify such waypoints. Use this option to the filter to toss known rogue points.
+</para>