<para>
This option specifies the maximum allowable error that may be introduced
by removing a single point. Used with the <option>length</option>
and <option>crosstrack</option> methods, the value of this option is a distance,
specified in miles by default.  You may also specify the distance in 
kilometers by adding a 'k' to the end of the number.
For the <option>relative</option> method it is a dimensionless quantity.
</para>
<para> 
How the error is determined depends on whether the <option>length</option>,
<option>crosstrack</option>, or <option>relative</option> method is used.
If you are using the length method, the error is the change in the length of
the route introduced by removing a point.  If you are using the crosstrack
method, the error is the distance from the point to the line that results if
that point is removed. If you are using the relative method, the error is the
ratio between the crosstrack error and the horizontal accuracy (derived from
HDOP data).
</para>
