There are three main types of data that GPSBabel deals with: waypoints, tracks, and routes. The nuketypes filter allows removing all the data of any or all of those three types.
Example 4.9. Filtering data types with nuketypes
If you have a GPX file that contains routes, tracks, and waypoints and you want a GPX file that contains only tracks, you may use this filter to remove the waypoints and the routes with this command:
gpsbabel -i gpx -f bigfile.gpx -x nuketypes,waypoints,routes -o gpx -F tracksonly.gpx
Remove all waypoints from data stream.
This option causes the nuketypes filter to discard all waypoints that are not associated with a track or route.
Remove all tracks from data stream.
This option causes the nuketypes filter to discard all track data.