<para>
This option computes a value for the GPS speed at each trackpoint.
This is most useful with trackpoints from formats that don't support
speed information or for trackpoints synthesized by the
<link linkend="filter_interpolate">interpolate</link>
filter.</para>
<para>
The speed at each trackpoint is the average speed from the
previous trackpoint (distance divided by time).  The first trackpoint
in each track is assigned a speed of "unknown."
</para>
<para>
The unit of speed is meters per second.
</para>
