GPX stands for GPS eXchange Format. It contains data generated by GPS devices.
We make such files available on our website. You can download them on your machine then read them with Google Earth or other geolocation software. We also sometime provide a simplified route (in kml), but the gpx is more exhaustive (in details and with time recording).
We keep a repository of our walks in the form of a big GPX file where we agglomerate all our recorded itineraries:
To add an entry, first edit it (with QLandkarte GT) and then from all-our-walks.gpx, Alt-A to Add-Geo-data (in the "File" menu). We put Spanish tracks in Yellow and UK ones in dark-brown.
While gpx files are better viewed with Google Earth, they are (sadly) better edited with other softwares. We like QLandkarte GT.
To retain as much as possible of the gpx information, it is best to Edit (right-click+'Edit') the track without converting it to an overlay (that is more easily edited if points are to be moved around), and then export to gpx.
This is achieved with gpsbabel, for any number of inputs:
gpsbabel -i gpx -f firstFile.gpx -f secondFile.gpx -f thirdFile.gpx -o gpx -F merged.gpx
Then, from within QLandKarte GT, which keeps them apart, these can be merged completely by Track->Join Tracks (F5).